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AUTO-POWERED ARC WELDER By Norman E. Schuttz

ENOUGH to be hidden beneath Sful'MALL the hood of a passenger car, yet powerenough to handle electrodes up to3/16-

in. dia., this 200-amp. welder is powered by the engine of the car in which it is installed, and can be taken anywhere that an automobile can be driven. The main component of the welder is a war-surplus Delco Remy P-l aircraft generator that is rated at 24 v. and 200 amp. at 2500 to 4000 r.p.m. Since this generator has a counterclockwise rotation, it must be turned end for end and driven from the commutator end when rotated by a car engine. This requires that the floating shaft, which drives the free-turning armature, be removed from the generator and modified. First, cut this shaft about 1 1/2 in. from the driving spline. Next, center-drill the end of a 7-in. length of 3/4-in. steel shafting to provide a press fit for the cutoff shaft. Force the 1 1/2-in. length into the hole in the new shaft and braze or weld it in place. Mill a 3/16 x 3/16-in. keyway 4 in. long in the end of the shaft to hold the pulleys and bore a clearance hole for the shaft in the end housing of the generator opposite the original location. The shaft

Above, welder connected and ready to run. Below, support frames bolted to head, ready for welder

WELDING MACHINES generator, One flange of the 1/8 x1 1/2 x1 1/2 in, channel is cut back to 1/2 in. as indicated. When assembling the frame, first mount the two self-aligning, pillow-block bearings on the shaft; then adjust the various frame members to keep the shaft aligned properly while they arc welded together. Front and rear supports for the generator frame are shown in Fig. 5. These supports were designed to hold the Frame above the spark plugs when they arc bolted to the head of a 1953 or 1954 "flathead'1 V8 engine, Fig2. Supports for bolting the generator frame to in-line-type engines and overhead-valve V8 engines will have to be modified or redesigned to suit a particular engine. Steel angles, spaced by lengths of 3/4-in. pipe, were used on the original supports. Holes in the bottom angles are 1/2-in, dia. to fit over the head bolts while holes in the upper angles are 3/8-in. dia., and are matched by holes in the generatorsupport frame. When considered necessary for more rigid mounting, a center support also can be used. Drive Pulleys A 3-in.-dia. double V-pulley is fitted on the welding-generator shaft. A 6-in.-dia. double V-pulley is welded to the crankshaft pulley of the car engine. Care must be taken in the latter operation to make sure the double pulley is centered on the crankshaft pulley to prevent misalignment. The center of the double pulley is cut out to permit tightening the pulley nut on the crankshaft Because the engine-fan will strike the modified pulleys, it is necessary to reposition it. Remove the blades from the fan hub, insert spacers and rerivet the blades to the hub as shown in Fig. 8. On a different type of engine, more or less modi-

fication of the fan may be required. When the fan is. moved forward it requires that the radiator be moved forward a similar distance to keep the fan blades clear of it. On the original car, four 5/8-in. hardwood blocks were used as spacers to relocate the radiator. Sheet-metal pans at the top and bottom of the radiator may require cutting or bending to allow the forward movement of the radiator. Arc Stabilizer and Rheostat To assure that the welder produces a steady arc, an arc stabilizer must be wired into the welding circuit. The stabilizer, Figs. 3 and 7, consists of a core of 2-in.-dia. cold-rolled steel approximately 5 1/2 in. long. First, a layer of insulating cloth is wrapped on the core, then five layers of 4ga. enamel-coated copper wire are wrapped on the core, each layer being separated by insulating cloth. Finally, the completed core is wrapped with tape and tied to make sure the wire stays wrapped tightly. The beginning and end leads are left about 9 in. long to permit attaching them to the terminals. Make sure the ends of the stabilizer core make good contact with the metal frame which is made of double 8-ga. sheet steel. Short flanges are bent along the edges, then mitered at the corners and welded to provide additional strength as shown in Fig. 7. The frame for the stabilizer also is used to support the rheostat, terminal connections and throttle for controlling engine speed, Figs. 3 and 7. The rheostat is a heavy-duty type, rated at 6 ohms, 11.1 amp. Fig. 6 is a wiring diagram, showing the connections between the stabilizer, welder and rheostat. Note that all wires in this circuit are 4 ga., except the lines to the Arc-stabilizer-rheostat assembly. Note how flanges are bent on stabilizer frame for added rigidity

WELDING MACHINES

Original engine fan was modified by removing blade

One method of controllong engine speed requires choke cable to which linkage is welded as shown

rheostat which are 14 ga. As shown in Figs, 1 and 2, the stabilizer-rheostat assembly is bolted to the inside of a fender. Large washers on the underside prevent the bolts from pulling through the sheet, metal of the lender. Throttle Hookup To control the speed of the car engine and thus the r.p.m. of the welding generater, it is necessary to add an auxiliary throttle control to the carburetor. As shown in Fig. 9. some cars are equipped with throttle linkage that has springloaded connectors that easily snap off without tools. An extra piece of the linkage is welded or brazed to the end of a choke cable that leads to the stabilizer frame where it is easy lo reach when operating the welder. To change from control by foot throttle inside the car to hand control at the welder' rcquires only unhooking one control and hooking on the other, On engines with other types of linkage connectors it may he possible to locate the 2436

from

hub,

adding

spacers, then

reriveting

blades

choke cable so that it can he hooked onto the throttle lever without the necessity of removing the regular foot-control linkage, hi some cases, the latter-type linkage is bolted together and requires the use of wrenches for disassembly, The less time required to connect the welder to the engine, the more time used profitably for welding, so it is important that any shortcut in making the hookup be considered, Operating the Welder Two heavy-duty V-belts are used to drive the welder from the crankshaft. Belts for the original installation were 54 in. long. Belts for other type installations are selected by measuring the distance around and between both sets of pulleys. To install the belts on the generator pulleys, the front pillow-block bearing is removed, both belts clipped over the pulleys, then the bearing is reinstalled. To fit the belts on the crankshaft pulleys, tip the forward end of the welder frame down, loop the belts over the crankshaft pulleys, then level the welder. Belt tension is adjusted by fitting thin washers or sheet-metal shims between the forward ends of the welder frame and the support frame. When the welder is to be run. continu ously for some time on a big job, connect the air scoop of the welding generator. Fig, 5. to the air horn of the carburetor with flexible tubing. Carburetor vacuum will draw air through the generator housing, thus cooling the generator. An ammeter and voltmeter are not wired into the welder, and since each welder will differ in characteristics due to being custombuilt, no precise calibration of the rheostat is suggested, After a few jobs with the welder, the operator will become familiar with the machine and can make his own calibrations, which can be marked on the frame under the rheostat dial, * * *

WELDING MACHINES-

HIS bandsaw, made largely of %-in. fir Tplywood, has a 12-in. swing, a tilting . table and cuts 2-in. stock with ease and accuracy. If it is carefully constructed, so that both wheels are in perfect alinement, you will have no trouble with the saw blade r q m b g off. The cost of building the original saw from wgch these plans were taken was four dollars. -.- For the base and core of the vertical frank pfeee, Fig.l,l%-in. yellow pine is used. The pattern for this part is laid out on a piece of heavy wrapping paper, as in Fig. 3. Cut the piece about I/s in. oversize, to Leave emugh stock for finishing. The plywood ,sides are then cut to size and glued to the core, using casein glue, after which additional strength at the edges is obtained by driving in wood screws. After the glue has dried, the edges of the £rame should be sanded on a drum or spindle sander. W e wheels are bhilt up of four 12-in. e

plywood

-5,

which are glued together

with the grain running crosswise to prevent warping. If desired, the outer, exposed disk may have its center cut out to £ o m a ring. Th6 6-in. pulley is similarly built up from.pl$wood disks, but the edge,

instead of being flat and covered with a rubber band, should have a V-groove. The hubs for the wheels and pulley are 4-in. ceiling-outlet covers, used in electrical conduit work. Drill a %-in. hole through the exact center of each, and screw them to the wheels as shown in Fys. 4 and 7, t a k i i care to get them on coricentrically. If a %-in. bolt, with the head 11

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BATTERY CHARGERS

DONT BE CAUGHT WITH A DEAD BATTERY

BUILD YOUR OWN QUICK-CHARGER By Patrick K. Snook

FEW MOTORISTS are able to put back what they take out of a battery during winter driving- The extra drain of coldmorning starts, increased use of lights and added heater consumption takes its toil and unless you do lots of highway driving, you can't hope to keep the battery up to par by mere driving alone. The in-town driver, particularly, will do well to have his own quick-charger which he can use on occasion to keep up with the increased battery drain that comes with winter driving. A simple quick-charger can be put together at little cost from odd parts that can be found in almost any junk yard. If possible, select a generator and voltage regulator from the same car—the generator being of the same voltage as that in your own car. You'd also better see if you can't

you've cleaned the generator thoroughly, make sure that the pulleys on both the generator and the motor are equal in size. The carriage, or dolly, which makes the charger portable, consists of a 3/4-in. board measuring approximately 12 x 27 in, which is mounted on an axle and two 8-in. wheels and provided with a handle. Mount the motor on blocks of 2 x 4 cut to conform and bolt this assembly to the dolly. To find the proper position for the generator, bolt it to its single mounting block, slip the 3/8 x 36in. V-belt over the pulleys and move the generator assembly back until the belt is snug when the generator inclines about 15 deg. toward the motor, This will enable you to mark the assembly's exact position. The generator then may be removed from its mounting block and the block bolted

BATTERY CHARGERS

the wiring, at) that remains to be done now is to fit the foot block and handle. The heavy-duty, two-wire power cable {No. 12 ga.) runs through the conduit and out of a hole drilled near the base, then under the dolly and up through a hole near the motor to which it is connected. Since most 1/4-hp, motors can be reversed make sure to connect the wiring so that the motor runs counterclockwise, viewing it from the shaft end. There are probably half a dozen different generator-regulator wiring set ups depending on the make and vintage of the car.

One possible set up is shown in the dia gram below. The generator terminals as well as those on the regulator are letter coded so that there should be no problems involved. One word of caution: On some models the field terminal is grounded by way of a resistor to the generator shell. In this case, mount the negative lead of the battery power cable to the screw that an chors the resistor, not to the field terminal. The direct lead from the field terminal should be attached to the F-post of the voltage regulator. * * *

201

OLD MAGNETO PROVIDES PARTS FOR BUILDING

Small

The compressor partly disassembled to show piston, connecting rod, and crank disk made from contact breaker

Workshop Compressor M

ADE entirely out of scrap materials, the small compressor illustrated will raise a pressure of 25 lb. per sq. in. in a 6-cu. ft. tank in 25 minutes, which is ample for the average small gas torch. The consumption of line-shaft power is very small, an important consideration in many small shops. Construction of the compressor is clearly shown in the photograph and large drawing below. Simplicity is the keynote of its construction throughout. The magneto which supplied most of the larger parts was purchased for fifty cents.

WORKSHOP HINTS

The method of procedure will be governed to some extent by the type of magneto available. Assuming the gear housing to be of cast iron and the end bearings to be of brass, it is a simple matter to saw and file out the gear housing to fit on the end bearing housing as shown. The two are fastened by a machine screw after being sweated together with soft solder. To do this successfully, the cast iron must be thoroughly cleaned and well tinned. The axis of the shaft hole in the gear housing must be kept parallel with the finished face of the brass base, Do not fasten these

parts together permanently at this stage. Chuck the base in the lathe and bore for the cylinder. The size depends upon the bushing used for a cylinder, but the drawing indicates the proportionate allowances to be made for shoulders and the like. The next step is to turn, bore, and lap the cylinder to an inside diameter of 7/8 in., with other dimensions to suit the actual bushing available. The cylinder bottom is soldered into place after fitting the simple ball valve. Make the valve seat very narrow, use a new ball, and tap the ball lightly on its seat before assembling to insure a tight valve. Mount the cylinder in the base and solder as shown. Care must be taken to see that the bore is at right angles to the finished face of the base. Note the aluminum cooling fins, which can be turned in the form of washers and threaded on the cylinder before mounting, with aluminum separators between them. The piston is built up from 1/8 in. sheet aluminum cut into disks 7/8 in. in diameter and riveted together. The rivets must be so placed that they will not interfere with the ring grooves or the piston-pin hole. The inlet valve in the base of the piston is retained with two turns of very light steel spring sprung into a groove just above the valve seat. The ring grooves are turned 1/16 in. wide and 1/16 in. plus .002 in. deep. The rings are 7/8 in. in diameter and 1/16 in. thick, split at an angle of 45 deg. and sprung over the body into place, care being taken not to deform them. The connecting rod is also built up out of the 1/8-in. aluminum sheet, two pieces being riveted together through the center section. The ends are left square in section as shown in the photograph and are fitted with bronze bushings for suitable pins, as indicated in the drawing. Care is necessary to insure that all joints are air-tight, because with such a small displacement a very small leak will seriously cut down the efficiency of the compressor. The best running speed is about 500 r.p.m. The lightness of the oscillating parts and the comparatively heavy driving pulley, acting as a flywheel, reduce vibration to a minimum, but the braces shown are necessary to give general lateral stiffness. They are bent out of 5/8-in. flat steel 1/8 in. thick, and fitted into place. 251

DRIVEN by means of a I - h p . electric motor, this homemade drillpress, built mostly from old auto parts and a few items obtainable from your local dollar store, is sturdy, accurate and smooth in operation. A cut-off portion from an axle housing is bolted to a brake drum, which, in turn, is bolted to the bench top. The spindle bearing is a small grinder head and is

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shown. The lower end of

Receptacle Built in Workbench 'it Extinguishes Lighted Matches --

direct to the motor. In either case it is advisable to use a three-step pulley on the motor to provide speed adjustment. Accessories such as the V-pulleys, belts and chuck can be obtained from almost any *

For Lathe Operators If you occasionally have a lathe job that requires resetting chucks frequently for

To avoid fires being started by matches thrown about his shop, after lighting gas burners and torches, one tinsmith installed this receptacle. It c o n s i s t s of a length of pipe run throughthebench top to end in a pail or can underneath t h e bench. A flange at the upper end of t h e pipe holds it in place. The lower end of the pipe must rest on thebottom of th into the pipe are and when filled, th the matches in the

wire remo small work, this simple speed wrench will save considerable time. It is nothing more than an ordinary hand drill with the chuck removed and the end of the shaft squared to fit the chuck screws. (rpunches and chisels for model makers can be had by grinding ice picks to shape,

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ILLING

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a

Just mount it on the cross slide and do keyway cutting, end milling and surfacing HIS handy milling unit for small metal-turning lathes consists simply

f a drill-press vise mounted on the

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of the carriage. The vise is a disk similar to the index disk ound rest, Figs. 1 and 2. Thus 0th the lateral and traverse e depth of the vise jaws gives a considerable range of vertical adjustment. Also the unit can be swiveled to any degree desired to handle angular work. Figs. 1 and 3 show typical operations on parts of small models. Milling cutters should be held in a collet chuck but if the lathe is not fitted with chuck and suitable collets, you can grip the cutters in a threejaw scroll or center chuck and, by working carefully, get very good results on light work. Figs. 4 and 5 show the base or pad on which the drill-press vise is mounted. It is turned from a single piece of cold-rolled steel and all the dimensions given adapt it to use on a well-known make of home workshop metal-turning lathe. Notice in Fig. 4 that the base is held in place with a hardened pointed setscrew bearing against the beveled projection on the underside of the disk. The setscrew lock is regular equipment on this particular lathe and the beveled projection on the vise mounting simply duplicates that on the regular compound supplied with the lathe as you see in Fig. 2, where the two parts are shown

Soldering With a Lead Pencil For small soldering jobs, you can effectively use an automatic lead pencil.

Wire the metallic part of the pencil to the negative pole of a 6-volt storage battery, and connect the positive pole to the work to be soldered. Then, touching the

point of the lead to the spot you wish to solder and then drawing it away slowly, will create a tiny arc. Use hard lead in the pencil, which should be a handle of bakelite or other heat-proof material. -Charles A. Younger, Somerville, N.J.

is, n o t d r i l l e d c through and are thre with a bottom tap. take full advantage of

chining the base so

much louder than a sigh. The barrel is encased in concrete 4 in. thick, the concrete assuring a good mufffer long after the thin sides of the barrel have rusted away.

am---- you want a smooth, polished finish on w turnings such as tool handles, first sand them carefully and then hold an oiled strip of cloth or leather against the work as it rotates in. the lathe.

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leg on which the coil is to be wound, multiplied by the thickness. In the case of the core shown, the center leg is .25 sq. in. The number of turns required is, therefore 493 divided by -25, or 1972. The y i r e size is calculated from the

length of the magnetic path, as shown in the upper detail of Fig. 7. The wire size in circular mils is found by multiplying the

length by 50,000, and then dividing by the number of turns. For a magnetic path of 3% in., the wire size required is 3.25 times 50,000, divided by 1972, or 82.5 circukr mils. The required gauge number is then found from any magnet wire table, which will show that No. 31 has an area of 80 circular mils, and No. 30 has an area of 101 circular mils. In such a case, the larger

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Bage number) should be Tha c d l will, therefoh, be wound with iPt2 tof No: 30 enameled wire. transformersap & mast g i v q Nos 3Q wire ere a heavy-duty @* built'kom large %stamplarlargm WWwill Be necessary.

size

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hb

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The d tg wauhd on a woodan form a9

5 w d 6. The form should b a h * Iarger thanthe 16g Qn which the cd*, rrnrl ,sh&tafso have a slight tag& e&, so th@the fbidhd,-coil , #pmd ,can b , r d l p g d - ' d readily aft@ misaving ' shorn in

The armature is fastened to its b r d with two flat-head rivets, counbrsunkL ia - ' the a~matupe.Clearances and specified should be followed cItre&By. & Eggraving tooh can be made of %-b,&.- , larger drill rod. The tips can be ground t~ various shapes, as shown in Pig, 2. After - ,. ~ough-grindingto shape, tb. end. shu]$ be hardened by heating to a straw yellow the aut'thg end om& into cold water. After hardening&er are An&& ground. The shank of the W1 can

color and pl-g ,

be h d e d ctnd l~crewedh t o the_end af the amnature; a h k nut and bc& w d i q are

b hold theni f r d y .

If & a &I-

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gle engraving bit is to be used, it can be held permanently in place by peening. The completed tool can be mounted on a semi-circular wooden block, and placed inside a fiber tube. See Figs. 1and 4. Another way to make a simple engraving tool is to take an inexpensive vibratortype (labeled' a.c. only) electric razor, of the kind which contains an electromagnet instead of a motor. See the left detail of

Fig. 7. Remove the cutter head from the shaver and, if necessary, saw off the end of the Bakelite case. An engraving tool can be attached to the vibrating shaft of the shaver. One way to do this is to swage the shank of the tool flat, and drill it to fit the shaft. It can be held in place by peening, or the shaft can be threaded and the tool tapped and held with a lock nut.

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Jackshaft on Motor Makes VariableflSpeedUnit

on an electric motor, The unit can be fastened in a fixed position for driving power tools, such as metal-turning lathes, drill presses, etc., where various speeds are required, or it can be carried about for operating a flexible shaft as shown. By using two 5-in. cone pulleys and a motor of 1,750 r.p.m. on the original unit a speed range of 700 to 4,375 r.p.m. was obtained.

Pillow blocks serve as bearings for the shaft, and they are bolted to angle-iron supports, which are attached to the motor' by placing them under the nuts of the tie rods that hold the motor housing together. In some cases, it may be necessary to substitute longer tie rods for the original ones. -Kent H. Alverson, Niagara Falls, N. Y.

Small Paper Cups Have Many Uses in the Home Workshop An inexpensive convenience in your home workshop is a supply of small paper cups. They are particularly handy when

away when a job is finished. Labels and measures can be marked on them easily with a pencil, and liquid levels show clear-

doing small jobs of finishing, er in mixing

ly through the translucent sides.

paints and stains. When tin cans are used for this purpose they always must be cleaned for the next job, and frequently bits of skins or traces of the old color remain. But paper cups are merely thrown

(TTo remove rust from the flutes of an auger bit use a small rope which is coated with glue or shellac and sprinkled with fine emery.

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Rubber Heels Cushion Motor

To reduce vibration of electric motors motor mounts for floating-type rails can be made from a pair of rubber heels. Cut a metal plate to fit the recess in the top of the heel and drill two holes through

to a minimum, eksek-absorbing

the heel and plate to line up with rail clips. Countersink the flat-herd bolt6 in the plate and bolt the three together. Fasten the heels to the bench with three screws or bolts, using washers under the heads.

supports the intermediate and top pulleys turns in sets of %-in: babbitted split bearings. Note that setscrew collars are used on each shaft. One face of the top or driving pulley is fitted with a counterbalancing steel plate as in Figs. 2 and 3.. The counterbalance is bolted to the pulley. Con-

and screwed into a tapped hole in one end of the counterbalance and through the pulley. This crankpin is secured with a

serves as a driver for the connecting rod which is made from a length of +!!-in. standard pipe. The forward end of the connecting rod is drilled for a %a-in. steel wrist pin threaded at both ends for lock nuts. The assembly is made as in Fig. 3. To guide the hack saw in a straight path,

an S-shaped bend in the arm as in Figs. 2

and bend carefully in a vise. Brass tubing

can be bent cold. The surface of the pipe which supports the hack-saw guide should be polished smooth. The slide is a length of brass tubing which will telescope over the polished section of the supporting arm. The hack-saw frame is fastened to the guide with the aid of clamps as in Fig. 2. These can be riveted to the saw frame or held with small bolts. The pressure applied to the blade when cutting is regulated by weights on the outer end of the supporting arm as shown in Fig. 1. These weights can be made by drilling a hole in cold-rolled steel plate of such a size that the piece will slip easily over the pipe. Setscrews 'or pins can be

screws. Fig. 4 shows the assembly of the speedreducing drive. All pulleys are of the V-type for %-in. belt.

Shaped from a p i e c e of t h i n ent materials require slight variations in blade pressure for the best-cutting action. The support-arm guide, Fig. 3, can be made .from %-in. flat iron, the slot being of the3same width as the diameter of the aipe. If necessary, the guide should be blocked up on .the bench, so that the arm will reach the bottom of the slot just as the saw breaks through the work. A standard toolmakers' vise can be used to hold the work. A slotted plate fitted in

you to start Screws in places where it is impossible to reach with the hands- A slot

with a hole at one end permits a screw head to be inserted and held true for starting it straight.

Power unit is simple box built from scrap to house small transformer and silicon rectifier. Cord at right plugs into wall outlet. Center cord (from rectifier) is positive, clips to work; one at left, to stencil pad.

Make an Electric You use a common mimeo stencil, but the printing agent isn't ink —it's an electrochemical flow By ROLAND LOEWEN

Y ou can easily—and safely—put electrochemistry to work "branding" your name

on tools, or decorating aluminum sheets. The stencil pad consists of a metal plate (copper, aluminum—even a scrap of tin can) covered with felt that's saturated with a solution of table salt (or with liquid Sani-Flush). Over this pad you smooth a section of an ordinary mimeograph stencil (available at any office-supply store) which you have typed on a typewriter set for stencil cutting, or with a hand stylus—just as if you were preparing it for inking. Clip the leads from a DC power source to the stencil pad and the workpiece and press the two together for 10 to 90 seconds. This power source can be your auto battery, a battery charger, or an electroplating unit. Or, to use house current, you 154

POPULAR SCIENCE

can easily assemble a unit costing under six dollars from a small transformer, a silicon rectifier, a few feet of insulated wire, a male plug, and two alligator clips. The power needed is at only six to 12 volts low amperage. I use a filament transformer from Allied Radio (their stock number 54C1420) that's rated 110-120 volts primary, and 12.6 volts at two amps secondary. I get about 12 volts, which speeds up etching jobs. I made two types of stencil pads—a oneliner to hand-hold against tools and a block against which metal plates can be pressed. Both are sketched at right. For the one-liner, glue the metal plate to the slightly rounded edge of the wood strip with epoxy cement, letting it extend at one end and bending it up as shown for attaching an alligator clip. Fasten a strip of felt over the metal, gluing it lightly. To use, soak the felt in the salt solution, then dab with a cloth to remove excess. Center stencil over felt so the lettering is backwards as you look at it. Tuck ends under a big paper clamp. The larger rig has two spring-loaded bars for this purpose; they seat in rabbets. Be sure your stencil is large enough to cover the felt or you'll leak current at the ends.

One-line stencil pad (left) is secured by spring clamp, as shown in sketch below. It's fine for applying name to hammer (above, with clip applied) or to steel punch and chromed tape case (far left, facing page).

Block-type stencil pad offers etching area about 2½" by 4"—ideal for address plates shown above. You induce electrochemical flow by holding positive clip in contact with back of plate centered on stencil.

Stencil to Etch Metal How electrochemical etching works Metal plate of stencil pad becomes cathode, charged with negative electricity (electrons). Above this (in cross sections below) is felt pad soaked in salt solution (sodium chloride: NaCl) plus a waxy stencil. Where latter is pierced, chlorine ions flow through to carry electrons to anode. Iron workpiece reacts with chlorine to form iron chloride (FeCl3), which dissolves, leaving mark. Other metals react similarly.

NOVEMBER 1968

155

Engineer's Level D

ESIGNED to be easier to operate and capable of taking more abuse than a transit, this engineer's level can be used for such outdoor j o b s as landscaping, septic t a n k installation, drainage ditching, setting c o n c r e t e forms or any task requiring level or grade s i g h t i n g Using engineer's level on a camera tripod to set concrete forms. (Fig. 1). It can be made in o n e By THOMAS E. RILEY evening with hand tools. The instrument consists of two major parts: The sighting level tube or telescope to which a level vial is attached, and the level bar. It. is supported by a camera tripod with or without a tilting head. The tilting head will enable the user to set up the instrument more easily but, on the other hand, detracts somewhat from the stability. Make the level bar (Fig. 2) first. Use angle iron taken from an old bed rail because structural angle iron is too heavy and thick at the corner. With a hacksaw make a cut 2 in. long as close as possible to the vertical side. Then bend up the 2 in. cut end. blunt knife edge. Finally draw the file lightly Since the bed rail steel may be brittle, heat the across the length of the knife edge to be sure the area to be bent to a dull red. Check the bent end edge is a straight line parallel with the bottom. with a square to make sure it is exactly 90° and This knife edge is the one crucial point in the saw off the extending vertical side 1/8 in. beyond construction of the instrument because it serves the bent section. File the top edge of the bent as the "Y" support of the level, the pivot bearing end down to 1 3/4 in. above the bottom edge of the and horizontal crosshair. Drill the two 9/32 in. bar and parallel to it. Then file both sides to a holes and tap the middle hole 1/4-20 to fit any camera tripod head. To make the level tube, cut pipe threads on one end of a 14 in. length of 3/4 in. standard pipe and saw the other end at an angle as in Fig. 3. Scribe a line lengthwise on the bottom of the pipe parallel with the sides. Measure and mark 11 15/16 in. from the threaded end for the location of the center of the pivot slot. Cut this slot 1/8 in. wide and file to the wedge shape (Fig. 3A). Round the bottom of the cut with a small rat tail file or abrasive cloth around a nail. The slot should extend exactly halfway through the pipe. Now lay out, drill and tap the two mounting holes on the scribed line and mark the optical center point. 128

SCIENCE AND MECHANICS

An ordinary 3-3 1/2 in. replacement level vial for a carpenter's level is to be used. Purchase the vial first then secure a piece of copper or brass tubing just large enough so the vial will slide into it. Cut the tubing off 1/2 in. beyond each end of the vial and file an oval hole in the middle of the tubing to expose the vial bubble as in Fig. 4. Drill parallel 1/8 in. holes in each end of the tube for supporting bolts and cement the vial in the tube with household cement. To locate the exact position the vial is to be fastened to the sighting level tube, hold the center of the vial bubble marking at the optical center mark scribed on the sighting tube and spot mark the locations of the two 1/8 in. holes in the copper or brass tube on the sighting tube. Drill and tap the sighting tube for 5-40 threads. Make the sighting disc Fig. 4 next. Cut a 15/16 in. dia. disc from 1/16 in. thick brass or steel. File and fit this disc to fit snugly inside a 3/4 in. conduit pipe bushing. Drill a small hole (about #55 to #60 drill) through the exact center of the disc and assemble to the threaded end of the sighting tube. It is important that the disc be secure. If the small hole is slightly off center, the final adjustment of the instrument will correct the error; but, if the disc moves after adjustment, the instrument will give false readings. Before assembling the parts give them a coat of paint. A crackle finish type of paint used by radio repairmen will give the instrument a professional appearance. Do not paint the knife edge or pivot slot. After the paint dries, cut the heads off two 5-40 x l 1/4 in. long machine screws and screw into the tapped holes in the sighting tube. Lock the screws to the tube with a nut on each one (Fig. 4). Place another nut on each screw, then the level vial tube and fasten with a third nut on each screw. Adjust the nuts on either side of the vial tube until the vial appears parallel with the sighting tube. Next, cut the head off a 1/4-20 x 2 in. bolt and screw into the tapped hole nearest the sighting disc or eyepiece of the sighting tube. Lock in place with a nut on the outside of the tube. Slip a lV4-in. compression spring and washer over the bolt and assemble the tube in its position on the level bar with another washer and wingnut. Attach another 1/4-20 x 2-in. bolt into the tapped hole nearest the pivot slot with a nut on the outside as before. Place a 5/8-in. compression AUGUST, 1956

spring, washer and nut underneath the level bar (Fig. 4). Screw the bolt into the tube until the spring exerts tension on the knife edge bearing. Then lock the bolt to the sighting tube with the nut on the outside of the level tube and the instrument is assembled. The level is adjusted by the collimation or peg adjustment. The object is to place the axis of the level vial exactly parallel to the line of sight through the level tube. You will need a surveyor's level rod for this adjustment and also for your surveys. One can be made inexpensively by purchasing a level rod ribbon and gluing it to a 1x3-in. board. These ribbons are l 1/2 in. wide cloth tapes with easily read graduations in hundredths of feet instead of inches. They may be purchased in any engineer's supply store. Set up the level in a convenient area outdoors. To set it up properly, place the legs of the tripod or adjust the tilt head by eye so that the bar seems level. Next, sight the instrument on the level rod and then center the bubble in the vial by means of the wing nut. Have an assistant balance the level rod on top of a stake driven in the ground fifty feet in front of the instrument. Sight through your level at the rod, and, after carefully centering the bubble, record the reading made by the knife-edge on the rod. The assistant rodman, then picks up his rod without disturbing the stake and moves to a point fifty 129

feet behind your instrument. Here he drives a second stake in the ground and balances his rod on it. You now swing your level around and sight on the rod again. Record this second reading after readjusting the bubble. Next, pick up the instrument and set it up directly alongside the second stake. Measure up from the top of the stake to the small hole of the eyepiece after the level bubble is centered. Even though your instrument was not yet in adjustment, your first two readings gave you the actual difference in elevation between the two stakes Why? Because equidistant level shots eliminate the collimation error and your two shots were equidistant. Now, if you add or subtract the difference in elevation (whichever it is) to the height of your instrument above the second stake, you will know what the instrument should read on the rod when the rod is on the first stake. With the rod balanced on the first stake, adjust the level tube with the wing nut to the correct reading, disregarding the bubble in the vial. Then without disturbing the level tube, carefully adjust the level vial with the four nuts until the bubble is centered. Your instrument is now in adjustment and ready to use, but the procedure may be repeated for a check. When observing through the level, always sight so that the rod is in the center of the horizontal knife edge. At that point any possible divergence of the knife edge from a horizontal line will be zero. A few hours study of a manual on surveying will acquaint you with the many uses of an engineer's level and with the procedures used by surveyors on complicated layouts of grade.

spark has an intense heat and actually eats into the metal, thus causing a permanent mark on the metal. To write well with the electric pencil will require a few minutes of practice. At first you will notice that the point tries to stick to the metal tool. You will learn to write with just the correct pressure so that an arc is continually jumping the gap. An electric welder must learn to strike and hold an arc as one of the first lessons in welding.

Fig. 15-21. An electric pencil is a useful tool for writing names or identification marks on tools and metal objects.

ELECTRIC PENCIL

Construction Hints: 1. Your first consideration in making this pencil is to keep the size small enough so that it may be easily handled as a pencil. 2. Fig. 15-22 gives you a detailed drawing of one way that this can be accomplished. 3. The core is a 16-d. nail, threaded on one end, on which is cemented two 3/8 in. fiber or plastic washers, to act as coil ends. The coil is wound with two layers of #18 enamel covered wire. One coil end runs to the connecting terminal at the end of the pencil. The other coil end is attached to the moving armature. 4. The armature is made of 20 ga. spring brass 1/4 in. wide, cut to suitable length. 5. The end of the brass armature is drilled for a 1/4-6-32 bolt. The bolt serves two purposes. It provides a piece of iron which the magnet can attract and also provides a means of attaching a short

Project IX This is a real practical project. You will find many uses for it around the home and shop. By means of the electric pencil, you can write your name on any metal object. Tools with your name permanently etched on them are easily identified. See Fig. 15-21. Two additional electrical principles are demonstrated in the construction of this project. First, a current flowing through a coil or inductor resists a change in the value of current. This property of a coil is called inductance. In the electric pencil when the circuit is broken as a result of magnetic action, the current attempts to continue flowing as a result of the inductance of the coil. This results in a small spark which jumps across the gap between the pencil point and the tool on which you are writing. Second, an electric COIL-#18 WIRE

DOWEL

16 D NAIL

BRASS ARMATURE

FIBER WASHER

WASHER FLAT ON ONE SIDE TO ALLOW ARMATURE MOVEMENT Fig. 15-22. Construction plan for an electric pencil.

94

Electricity - PROJECT SECTION piece of copper wire to be used as a writing point. 6. After the pencil assembly has been made, it can be fitted into a 6 in. length of 3/4 in. dowel. See Fig. 15-22. Mount the dowel in a lathe and bore a 3/8 in. hole in one end of sufficient depth to take the coil. Then drill a 1/8 in. hole all the way through the dowel for the connecting wire.

7. To use the pencil, connect one terminal of a 6 v battery to the tool on which you wish to write. Connect the pencil to the other battery terminal. When the pencil touches the tool, the circuit is closed and a current will flow, creating magnetism which draws the point from the tool, which opens the circuit. The point then touches the tool again. The resulting arc will mark the tool.

SPRING HOLD-DOW

I

can is splashed by the crankshaft to keep the mechanism weII lubricated. The complete drive unit is shown in Fig. 1, partly cutaway so that you can get a better idea of its assembly. Bronze spindle bushings (Ford model-T type) are used as sleeves for the vertical shaft and also as SCARCITY of metal leed not keep you a bearing for the crankshaft. Fig, 3 shows from having a scroll 'saw, as this one is how the channel is clamped to flattened mqde mostly of wood. Abide from the bolts places on the shaft, and how the lower and bushings required, t p few other pieces bushing is mounted in a flat-iron bracket. of metal needed can be,salvaged, in most Note from Fig. 4 that the bolts in the latter cases, from odds and efnds found in the fasten both it and the can to the wooden junk box. If plywood i;s not available in base. YOUcan work the channel to shape your particular locality,l you can resort to by hand using a hacksaw, chisel andefile, solid stock by gluing up panels of sufficient or YOU can have the channel and crankwidth. The crankshaft mechanism of the shaft made. Thick felt washers prevent drive head operates in la bath of oil and leakage of oil at points where the two , is sealed inside an ordingry 1-qt. paint can shafts pass through the can. The oil level, of the type having a p ess-fit lid. Fig. 4 of course, should be kept below the hole will give you an idea o how it works. A in the side of the can, as shown in Fig. 4. crankshaft, entering the side of the can, It is important that the block holding the rth crankshaft bearing be rigid. Fig. 2 show a way of bolting thii, which allows it be retightened easily if it should w loose. When insfaJling the crankshaft must be no end play, as the face of the

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TO LEG REACH

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the top of the plywood sides. With this filler block in place, you can go ahead and add the blade chuck to the slotted end of the shaft. This consists of a hexagon nut screwed and soldered to the end and then drilled and tapped crosswise for a setscrew to clamp the blade as shown in Fig.7. The blade can be made self-centering in the

a %-in. elbow to be pinned to the projecting end and soldered to'the flange. If you are unable to have the bushings turned of metal to fit the pipe shaft, satisfactory ones

width as the blade. pipe shaft by two floar flanges which are centered and screwed opposlte each other. One end of the shaft is threaded to pass throu+hGp flanges far enough to permit c.z:*-

, ; : b 4

i f short pipe arms make a neat job. to the size of the plywood drive you'll have to true it on the outer . the lathe as shown in Fig. 10.

:

ins Hold Bandsaw Blade in Vise While BI Instead of making up a special jig to hold the ends of broken bandsaw blades in perfed alignment while brazing, just slip a couple of large cotter pins over the blade and clamp them in a vise as shown. To protect vise jaws against excessive heat from them in the visl

SLOT PERMITS ' TILTING TO ANGLE OF TABLl

tracking without twist by engaging a cross pin in the shaft in slots in the tube. Needless to say, the slots in the tube must be cut down each side exactly in the center, otherwise the pin is apt to bind or prevent assembly. The shaft, with the cross pin either threaded or pressed into it, must be slipped inside the tube and both inserted in the hole at the same time, after which'the spring is added and the lower bushing and its

As -, portan ant that the holes be in lime centrally through the block, a drill press, is preferred to boring them by hand, although the Iatter can be done fairly accurately if you are careful to keep the bit running as straight as possible. Bore the top hole 3 in. deep, then turn the block end for end, and with a 1-in. bit, bore through to meet the first hole. Next, groove the rear edge of the block to take the holddown, after which the uppet. corner is notched according to the dimensions given in Fig. 15. The cutaway sectional view in Fig. 15 ahows what the tension mechanism looks like when installed in the counterbored housing. Bronze bushings of the type that were used in the drive head are used here to carry the shaft; the upper bushing being pinned to the block through the flange and the lower one bushed centrally in the hole with a turned wooden sleeve. Fitting the

sleeve are pressed in the end to hold the tube in place. The width of the slots in the tube should equal the diameter of the cross pin. Note that a thick felt washer is provided between the bushing and the metal plate which holds the former in place, to prevent oil from being thrown out through the shaft clearance in the plate. The upper blade chuck is made the same way as the lower one, which was described previously, the end of the shaft being threaded for the nut before the shaft is installed in the housing. A turn of a handwheel clamps the unit securely-in the arm. This can be made of wood and fitted with a carriage bolt to engage an embedded nut in the opposite side as shown in the top view of Fig. 15. The completed unit must be mounted in the arm so that the upper chuck will be directly in line with the lower one. You can do this best by clamping the unit ten

..

porarily in place with a C-clamp or a handscrew and checking it for alignment with a square held along the underside of the arm. When centered, the frame core piece along the top of the arm is fitted and bolted in place behind the unit and filler blocks or stops are glued between the sides at the front. See top view, Fig. 15. The work hold-down, Figs. 15 and 16, is improvised from an old table fork having the two center tines removed. It is soldered to a 1%-in. disk slotted crosswise, to permit the hold-down to be adjusted to whatever slant the table may be tilted. The fork and disk are held to a wood shaft by a bolt blade guide. Several of these guides will be needed to accommodate blades of various thicknesses. .You can make them easily from %-in. carriage bolts by slotting the heads the required depth with a hacksaw and then closing the slot slightly by peening it to suit the blade thickness. A thurnbnut fitted as shown in Fig. 15 serves to lock the hold-down at the desired height, and wax applied to both the shaft and the channel in which it moves will make it slide easily. Making the trunnions for the tilting table will require the use of a lathe, as a groove must be turned in them to take guides on which they move. Both trunnions can be had from one plywood disk by sawing it carefully in half after turning to size. Note in Fig. 18 that the bolt slots through $he trunnions must be cut on opposite sides of the centerline to obtain right and left-hand units. Use hard-pressed board from which to turn a ring to fit the trunnion grooves nicely and then screw - 3-in. segments of the ring flush with the top of the frame at the front and back as shown in Figs. 19 and 20. Notice that the square heads of the trunnion bolts are embedded under the guides before screwing the latter in place. A wing nut and washer are provided on each bolt to lock the trunnions in position. Wax applied to the trunnion grooves and the guides will make the table tilt smoothly. Plywood is preferred to solid stock for the table, as it will stay flat. It is attached to the trunnions with cleats as shown in the upper detail in Fig. 18. You will have to do this, of course, while the trunnions are in place on the guides. The recess for the metal table insert is formed easily by pressing a turned ring in the hole as shown in Fig. 17. Hera you also can see how the frame extensions

( @$ FRONT VIEW SHOWING TABLE TILTING TRUNNION

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provide stops to permit returning ble quickly to a horizontal position. it is desired to have the table so it tilted 45 degrees to the left ako, th can be cut off. With this arrangeme clamping-bolt slob are extended an trunnion indexed 90 degrees for ra settitig. If you are unable to buy an endless belt long enough to reach the drive pull you can resort to round leather belting even sash cord, applying belt dressing slippage develops. , r

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Ball-Bearing Mandrel From Bike Pedal Hanger

With very little olterotion, o bicycle hanger assembly provides o rugged, inexpensive boll-bedring mandrel for a homemade power grinder, circular saw and similar high-speed tools

If you are planning a homemade tool that requires the use of a mandrel, such as a grinder, table saw, etc., the pedal-bearing assembry of a discarded bicycle will provide a ball-bearing mandrel that is free running,and dust tight. Saw the frame to sever the hanger and weld the remaining stubs to a metal plate to simplify mounting the assembly. Then remove the pedal

cranks and turn down the projecting ends of the shaft to the desired diameter; usually a %-in. diameter is the most suitable. Threading the turned ends of the shaft so that nuts can be driven on in the direction opposite that of the rotating saw or grinder, completes the job. If desired, a grease fitting can be fitted on the housing to simplify lubricating the bearings.

Drill to Use in Model Making Assembled From Scraps. This handy drill for use in making model ships, planes, etc., is constructed easily. A 7-in. length of %-in. brass or steel rod is used for the shaft, and a spiral, removed from an automatic lead pencil, serves as a rotating device, which is soldered at the ends to the brass shaft. A finger grip, which rotates the drill when moved up and down the spiral, is made from a %-in. length of brass rod. This has a hole drilled through the center so it will slide loosely over the spiral, and is fitted with a pin, which extends slightly into the center of the hole to engage the spiral. The chuck is one removed from a small pin drill. Drill bits are made from steel sewing needles. r

Here's the completed furnace set up ready for use. The burners have separate gas valves to provide precise adjustment of the flame. A single valve controls the air supply from the vacuum cleaner. Although not pictured, the molding flask should be placed near the furnace

Gas-fired smelting furnace By

E.

R.

HAAN

W I T H THIS SMALL FURNACE you can melt down aluminum, brass and copper; preheat small, thick pieces of iron and steel for brazing or forging; caseharden soft steel; make up alloys and bake vitreous enamels on metals. You can use either LP or city gas. The cost runs from $25 up. The refractory lining: Build the refractory lining inside a sheet-metal can from 11-1/2 to 14in. in diameter, and from 14 to 17 in. high. Drill and ream two 3/4-in. holes diametrically opposite each other as indicated. Then cut 5 pieces of firebrick to the sizes given for the furnace floor. To

cut firebrick neatly you score it all around at a marked line by tapping with a sharp cold chisel to form a groove 1/16 to 1/8 in. deep and then break with a heavier blow. The refractory lining consists of ganister and pieces of firebrick. Ganister is a mixture of equal parts of pulverized firebrick and either prepared refractory cement or fire clay. The mixture should have the consistency of rather stiff mortar. If you use prepared cement, you will need two 1-gal. cans. If you use fire clay, you add water sparingly. Pieces of firebrick usually can be had at little or no cost from a brickyard. Pulverize these with a hammer. Cover the bottom of the can with ganister about 1-1/4 in. deep, and tamp it down to eliminate air pockets. Place the 5 pieces of firebrick in the positions shown, press them down into the ganister so that their top surfaces will be level 1/4 in. below the holes in the sides of the can. Press ganister into the spaces between the pieces of firebrick to come 1 in. from their tops. Next, make the cylindrical inner form of sheet metal.This is 7 in. in diameter for a can of 11-1/2 to 12 in. in diameter so the lining will not be less than 2-1/4 in. thick. The inner form is 8 in. in diameter for a 12 to 14-in. can. Hammer the seam moderately tight so that it can be pried open for removal of the form. Drill and ream

two 3/4-in. holes diametrically opposite each other and 1/4 in. above the bottom edge. Place the form centrally on the furnace floor so the holes are in line with those in the can, and push an 18-in. length of 3/8-in. pipe through all the holes. Now you build up the lining. Set 8 to 12 lengths of wire or old hacksaw blades vertically at the center of the lining for reinforcement. Tamp the ganister into all voids and in good contact with the can, inner form and pieces of firebrick. After the lining has dried overnight, turn out the pipe and remove the form. Then let the lining cure for three days. Burner details: The 3/8-in. nipples of each burner should come 1/4 to 3/8 in. inside the surface of the lining. A similar amount of clearance is allowed between the reducers and the outside of the furnace. The brass half unions fitting the tees are the kind used to attach 3/8-in. copper tubing with compression nuts. Enlarge the inner part of the hole at the beveled end with an 11/32 in. drill to a depth of 1/4 in. To do this you mount the fitting at a true perpendicular in a drill vise and do the drilling on a drill press. Tap the enlarged portion of the hole with a

Tongs should be designed to grip the crucible firmly when removing it from the furnace. Be especially careful when pouring hot metal into the flask

1/8-in. pipe tap to take a nipple which should extend 1/4 in. inside the end of the burner when it is assembled. The nipple has four No. 45 holes drilled equidistantly through its wall as shown. A steel sleeve fits the burner end of the nipple and a brass bushing, drilled centrally with a No. 45 drill, fits into the other end of the nipple where it screws into the half union. Pipe and tubing unit: Use 1/2-in. pipe for the air supply line and 3/8-in. copper tubing for the gas supply line. Compression fittings were used on the tubing in the model shown. For these the ends of the tubing must be flared carefully with a flaring tool to produce tight, nonleaking joints. Each burner has a separate gas valve for individual adjustment of each flame but a single air valve serves both burners. Having the air and gas supplies connected midway between the burners equalizes the resistance of pipe and tubing.

If the rubber hose for the gas line is too small to fit on 3/8-in. tubing, make an adaptor from short lengths of tubing, one fitting inside the other, then sweat-solder together. Also make an adaptor of close-grained hardwood to fit into the end of the vacuum-cleaner hose. Pipe-joint compound is used only at the tees where the half union and reducer screws into the tees, and where the 3/8-in. burner nipples screw into the reducers. All the joints of the gas line should be tested. Crucible, tongs: A graphite-clay crucible is best, but for economy you can use one made up from a malleable-iron pipe cap and nipple of suitable size. A 3-1/2-in. pipe cap provided with a 6-in. nipple were used for the model shown. By providing the pipe cap with 4 machine-screw legs turned into tapped blind holes in the bottom to raise the crucible 1/2 to 3/4 in., the flames will meet under it and the heat will be absorbed faster than if the flames contact only the side of the crucible. Curvature of the jaws of the tongs depends on the crucible diameter. The contact should be, uniform and the tongs should be tested for holding before being used. Curing the lining: After the 3-day drying-out period you ignite the gas and allow small flames to burn without any air blast for about an hour to complete the curing of the lining. To ignite the furnace place a lighted match inside near a burner and turn on the gas supply slowly to produce a small flame. Then turn on the other burner to ignite from the first and turn it down for a small flame. After an hour's time the air blast is used for about 10 minutes. First open the gas valves farther so that the flames will rise above the furnace top. Then, while the air-supply valve is closed completely, turn on the vacuum cleaner, after which you open the air valve slowly until the flames become light blue. Too much air in proportion to gas will extinguish the flames. Avoid this by turning the gas valve almost fully open, then turn the air valve wide open after which you gradually decrease the gas supply to each burner to reach the point of maximum blast without flame flutter. After 10 minutes close the air valve first and then the gas valves. When the furnace has cooled you inspect the lining for cracks which are almost certain to develop. Fill the cracks with prepared refractory cement or fire clay and allow this to dry out before the next firing. Crack filling is repeated if more cracks develop. When operating at maximum blast, the furnace can be covered almost

entirely with a piece of asbestos-cement board to retain heat. To inspect the charge you remove the cover with a pair of tongs and observe the contents of the crucible through colored glasses. Use the skimming ladle to drop some borax into the molten metal. Use technical grade borax available at photo-supply houses. Skim off the resulting dross or scum before removing the crucible for pouring. Safety rules: An LP gas tank should be located outside the building, and the gas piped through a 3/8-in. copper tube provided with one gas valve at the tank and another inside the building. Locate the furnace on an earth or concrete floor that slopes away from walls or combustible material. The latter should be kept a safe distance from the furnace. A sheet-metal box about 6 in. high and about 3 ft. square, two-thirds full of dry sand, should be located next to the furnace. The molding flask is set on the sand. The crucible is held over the sandbox on its way to the molding flask for pouring.

TURDINESS and accuracy are incorporated in this inexpensive, rollerbearing grinder, which you can make from an old auto-differential assembly. The grinder will take wheels up to 12 in. in diameter, and it can be made either in a floor or bench type. The work can be done with ordinary tools with the excep-

Use glue between the

angle, it -is best to drill them with a -in. bit, and then. enlarge them with a earner. In order to tighten the bolts efively, sleeves are cut from M-in. pipe placed over the threaded ends of the between the kt-iron supporting bars the housing as in Figs. 4 and 6. One of each sleeve is beveled so that it fits ugly against the housing. The assembly f the wheel guards is shown in Figs. 8 9, the latter giving the essential disions. The wheel guard is bolted to supporting bar at the back. It is not ened to the housing. The balance of assembly for the floor-type grinder overhead belt drive is clearly shown ig. 5, while the bench type is shown y requires that the speed of 12-in. g . wheels should not exceed 2,000 1,800 r.p.m. is better for a wheel diameter. Smaller wheels can be proportionately higher speeds. f you have occasion to use a drill that is

small to fit pour brace, slip a piece of

Indicator for Setting Tailstoc Of Lathe at Zero Position After turning a taper on work by means of the tailstock setover method, you can move the tailstock back to align the centers without loss of time if this in-, dicator is used. It consists of a sheetmetal pointer pivoted to a pin in the .lathe bed, and a., length of spring wire, which is fastened rigidly in the pin and wrapped around wire causes the point stop pin in the tailstoc follows the pln. A f t r perfectly, mark the po end on the tailstock Then if the tailstock it back to bring the and !he centers will .

WELDER'S LRILLami G K 3 E R -

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O rent produced by a welding generator, this

By F. Gage PERATING on cur-

grinder and drill, Figs. 1 and 2, will be helpful to owners of motor-driven electric welding outfits who take them to farm

enpenditure is the cost of old auto starters. The drill and grinder shown here were made from model-T Ford starting motors, which are rugged and do not burn out easily. They can be operated safe1y on any d.c. welding generator having an open vdtage range-from 0 to 40 volts. When using the drill or grinder, b run the generator at idling speed of the motor that drives it so that voltage delivered will be low. A . little experimenting will enable vou to determine at what soeed

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. After obtaining the s t a r t i n g motor, take it apart and clean it thoroughly, washing the parts with gasoline if necessary. Then inspect the bearings, and replace them if they are worn. If desired, you can s u b s t i t u t e ball bearings for the bronze ones already in the motor. Also, check the brushes and replace them if they are worn down. If the commutator is worn, turn it 'down in a lathe, and undercut the mica, or else replace the armature with one on which the commutator is in good condition. Now, before reassemblini the motor, euk

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off the end slate and armature shaft as

indicated in ~ i g3.. Be sure that the armature shaft is straight and true. Then thread the end of the shaft to take a drill chuck. As these motors rotate in the opposite direction of a drill, they must be reversed. This is done as in Figs. 5 to 8

If-

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FROMWELDING

11

%Ef?,O%ac

inclusive. The end cover is given one quarter turn to the left as you face the closed end of the cover. In this way, the cover is turned so that the screw holes are moved to line up with the next holes in the housing. This makes it necessary to cut a

ackets to which they were connect, and then resolder them. In exing the brush brackets, you will e that two of them are insulated th fiber strips from the c-opper ring which they are mounted. The ds are connected to these brackBefore replacing the cover, drill a small hole in the end so that the hearing can be lubricated frequently. A little felt placed inside the cap in front of the hole will help distribute' oil to the bearing. This completes changes in the motor. Next, comes a pair of handles. These are pipe nipplks, which are screwed into sockets arc welded to opposite sides of the motor housing. The original sockets were made by sawing a pipe cou-. pling in half. Be very careful in doing this welding job to see that the motor housing is not heated enough to damage the insulation of the coil wires inside. One of the handles is fitted with a switch made as in Fig. 4, using heavy copper contacts. This gives instant control of the drill as the switch really becomes part of the handle and must be gripped to keep it closed. If the motor is to be used as a grinder, ,the treatment is the same except that the a r m a t u r e shaft i s threaded for nuts to clamp on a grinding wheel, and the hanare shaped from flat iron to provide s suitable for manipulating a grinder.

Notches Cut in Eye of Lathe Dog Adapt It for Square Stock new notch in the cover to straddle the terminal that projects from the housing. You can do this easily with a file or hacksaw. After the cover has been shifted, you will find that one of the coil lead wires is too

short to connect to its brush bracket. You

can lengthen it with a short piece of wire, of course, but a neater and better way to do the job is to unsolder the leads where they are connected to the field coils, and shift them as shown in Figs. 7 and 8, until both will reach the two insulated brush

Sometimes it is handier to drive s q u a r e stock i n a metal-turning lathe by using a dog instead of a chuck. Any dog suited for round work can be made to hold square stock by filing two small notches in the position shown. In most small dogs, several sizes of squares can be held in one pair of notches.

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Right: Boring tough automobile spring leaf with ordinary carbon drill after it has been case-hardened in a home workshop. Above: Samples of what case-hardened objects can do.

Photos by Panlel Hubin

HARDENING STEEL in the home workshop By Albert A. Brandt OW many times have you wished that you could put a tough edge on an H ordinary nail and drive it through a piece of—say, 1/8-in. steel plate? Now, using a non-poisonous alloy powder developed by Samuel D. Necamp, known as Hi-Speed-It you can do just that. The powder fuses into the metal and increases its surface hardness in a matter of seconds.

1. First step in case-harden ing; heat object to cherry red. 2. Object is then dipped into powder and stirred to insure even coating. 3. After reheat ing the object is quickly quenched in brine or clean cold water. 4. For greater depth of hardness the process is repeated again. 5. A Bunsen burner is being used to heat a dentist's burr for hardening.

No special equipment of any kind other than a gas ring or Bunsen burner is required. To harden iron and low-carbon steel with the Necamp powder, you first heat the object to a cherry-red color (between 1,400 and l,700°F). To ensure even heating, it should be turned or rotated while heating. [Continued on page 158]

Hardening Steel [Continued from page 107] The object is next dipped into the powder and stirred about until a thick coating adheres. From 15 to 30 seconds is allowed for the powder to fuse into the metal. The object is then reheated to a cherry red color and quenched quickly in brine or clean cold water. A second fusing and dipping into the alloy powder before quenching will give greater depth of hardness. The same procedure may be followed to case-harden cold-rolled or machine steel. After the powder is well fused into the metal, when case-hardening high-carbon steel, the object should immediately be brushed thoroughly with a wire brush or emery stick to remove excess coating. It should then be reheated to cherry red and quenched. With high-speed steel, the object is heated to a somewhat higher temperature— between 1,800 and 2,200°F (white-hot)—and is quenched in oil. Fantastic as it may seem, an ordinary nail can be hardened by this process so that it can be driven through cold steel plate, while chisels can be made out of ordinary bolts or cold-rolled rods. It is possible to harden a carbon-steel tool so that it will do the work of a high-speed tool and give a carbon drill sufficient hardness so that it will shear through automobile spring leaf, blue spring steel and other tough alloy metals. •

HIS utility bench not only supports T y o u r iqthe with unequaled stability but also provides plenty of storage space for accessories and other tools under a bench top of generous yet convenient dimensions. As an added attraction, we have installed a built-in air compressor for spray painting, but this is optional. The six slide-through drawers are accessible from either side of the bench and their interiors are fitted with partitions, blocks, clamps, etc., for the

orderly storage of tools and lathe accessories. Lathe-turning tools can be stored' in one of the shallow drawers to the right and within easy reach of the operator. These drawers will also house honing stones of various .sizes and shapes, rulers, calipers, tool rests, lathe centers, face plates and most of those other small and frequently used lathe parts. The deep drawers accornmodate grinding wheels, buffing wheels, sanding disks and other larger jigs and

TYPICAL DRAWER CONSTRUCTION DETAIL

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IO26~~~"dldllF MASONITE

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SLIDE-THROUGHDRAWERS can be opened from either side. Note dividing pdtion. built-in tool rack. .

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attachments for the lathe. C o n s t r u c t i o n of t h e bench is c o m p a r a t i v e l y simple: there is no complicated joinery involved. All joints are either butted or lawwed. The bench can be b d t entirely with hand tools although power tools simplify the job. Any s e a s o n e d lumber will m a k e a s u i t a b l e bench. In this case fir was used for the heavier members of the frame and No. 5 white pine for the drawers and drawer supports. A really good top can be . made by using hard maple

strips assembled on edge and bolted together. The height of the bench is 32% inches, which is about right for the average operator.-H. R. Clark

REAR VIEW of lathe bench shows the ample space available for the compressor mounted behiid motor.

Lathe Milling Attachment By L C. MASON

B

Y CLEVERLY stacking cold-rolled flat stock together, T-slots and slide for this lathe milling attachment are made without costly machinery. In fact, only two tools, a drill press and lathe, are needed to make the attachment. Shown mounted on the cross slide of a lathe (Fig. 1), the attachment features a swivel base and tilting slide which has T-slots for clamping the work securely in place. Although this attachment was made for a 7-in. Atlas lathe, the overall dimensions could be increased 25% for use with a 9 or 10-in lathe. Start by cutting the stock size cold-rolled flat stock for T-slot pieces A, B, C and D in Fig. 3 to 3-in. lengths. Then lay out and drill the #21 holes. Pieces A and B, and C and D can be clamped together when drilling so that they will line up properly when assembling later. Next, hacksaw the slide plate E in Fig. 3 to shape and trim up the cut edges with a file. Lay out and scribe lines on the slide plate for locating pieces B and D. Be sure these lines are square with the sides of the slide plate. Clamp the B and D pieces to the slide plate and drill the 12 #21 holes. Then open the holes with a #9 drill and countersink the holes on the back of the slide plate to sink 10-32 fh screws just below the surface. Tap the #21 holes in pieces A and C with 10-32 NF threads. Now cut the back plate pieces (F and G in Fig. 3) to length. Since stock size cold rolled 120

Milling attachment in use on 7-in. lathe for milling out parts in the manifold of a model 4-cylinder gas engine. One holding clamp removed for clarity.

does not come 2 3/16 and 1 11/16 in. wide, you will have to machine them. Clamp them on the lathe faceplate with a 90° angle block and turn the 2 3/16-in. piece about 1/64 in. undersize. Set these pieces aside for the moment, and make up and drill pieces H, J and K in Fig. 3. Note that the ends of piece H are filed to take the brass gib L, which should also be made up at this time. To assemble, first clamp piece J to the back and right side of the slide plate. The top and bottom screws securing piece J will run into the B pieces, so bolt these pieces on the front of the slide plate. Spot drill the slide plate through the #9 holes in piece J, then remove it and drill through with a #21 drill. Tap 10-32. To be certain of getting piece H parallel with piece J, place piece F between them. Be sure that the gib, piece L, is between pieces H and F also. Clamp piece H to the slide plate and test piece F to see that, it slides up and down smoothly. Then spot drill the slide plate through the holes in piece H and drill and tap as you did for piece J. Assemble the K pieces with the F piece in place. Now, place piece G, the other back plate you machined to 1 11/16 in. wide, on piece F between the K pieces. There should be 1/32 in. clearance on each side between the K pieces. Clamp the G piece in place, and drill the 3/16 in. rivet holes deep enough to spot drill the hole locations on SCIENCE AND MECHANICS

the F piece. Then remove the pieces and continue drilling the holes through the F piece. Countersink the rivet holes on the F and G pieces a good 1/16 in. and fasten with rivets cut from 3/16 in. dia. soft steel rod. Heat rivets red hot before setting. When cool, file or grind flush at both ends. Your next step is to true up the front, or top surfaces of the T-slot pieces A and C so that they will be parallel with part G of the back plate that fastens to the angle on the lathe cross slide. First remove pieces H, J and K on the back of the slide plate. Then permanently fasten T-slot pieces A, B, C and D to the slide plate. File projecting 10-32 screws flush with A and C pieces. Reassemble the riveted back plate to the slide with pieces H, J, K and L. Tighten the screws so that the back plate will not slide. Now clamp the assembly to the lathe faceplate, so that the back plate is against the faceplate and T-slot pieces facing outward. Take a series of light cuts off the surfaces of pieces A and C, which will true up the front and compensate for any difference in the thicknesses of the flat bar stock. For the feed screw, make up piece M in Fig. 3 and fasten to the top of the slide plate with two 10-32 fh screws as in Fig. 2. Do not drill the ¼-in. hole in piece M at this time. Also make the nut, piece N in Fig. 3, and fasten to the top of piece G with two 10-32 fh screws. Since the holes for the feed screw through pieces M, N and the back plate must be aligned and parallel with the slide ways, clamp the assembly in the upright position on the drill press table so that the front of the slide plate and right side of the slide way is parallel with the drill bit. If the drill press has a tilting table, be sure to square the table with the drill bit first. Using a #21 drill, bore a hole through piece N and M, and into the back plates about ¼ in. in depth. The hole should land right between the riveted back plates. Remove the #21 drill, chuck a ¼in. drill and bore through piece M only. Then, without removing the assembly from its clamped position on the drill press table, take off pieces M and N and bore a 9/32-in. hole 3 5/8 in. deep into the riveted back plates. While you have piece N off tap the #21 hole with 10-32 threads and reassemble to the back plate. Turn the feed screw, O in Fig. 3, from 3/8-in. steel rod, reducing the thread little by little until you have a shakeless fit with the nut. Note that the other end of the screw is threaded ¼-28 for the handle and dial. Turn the dial, P in Fig. 3, and scribe the graduations on the bevel with a screwcutting tool bit turned sideways in the 121

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tool holder set at center height. Twentyfive divisions on the dial will indicate slide movement of .002 in. for each division. A 25-tooth gear fastened on the lathe spindle was used for indexing. Scribe every fifth line (.01) the full width of the bevel. Make the handle pieces Q and R as detailed in Fig. 3, and turn the thrust washers from bronze or brass. Before assembling the feed screw to the slide and back plate, turn the mounting bolt 5 in. (Fig. 3). Use a stock ½-20 hex. nut with the bolt. Then remove the back plate from the slide and bore the ½-in. hole, countersinking the widest of the back plates to the same taper as on the mounting bolt. Try to arrange the work so that the taper on the bolt and back plate can be turned without changing the angle of the lathe compound rest. When assembling the feed screw to bearing block M on the slide plate, place a thrush washer on the feed screw shaft at each side of block M. Then screw on the dial and handle on the feed screw, allowing just enough play for easy turning. With the handle and dial locked together like locknuts, hand solder or braze the handle to the dial. Drill a 1/16-in. hole through the handle and feed screw and drive a pin through it. Scribe an index mark on the slide plate as on E in Fig. 3. When assembling the mounting bolt to the back plate, file notches in the bolt heads as in Fig. 3. Then, after inserting the bolt in the back plate, raise burrs with a centerpunch at the edge of the hole to fill the filed notch. This will keep the bolt in place and prevent its turning. Now place the back plate in the slide ways, engage the feed screw and work it back and forth a few times to test the slide ways. If the K pieces are too tight, place a paper shim under each for clearance. If too loose, file or grind down the thickness of pieces H and J. Adjust the gib screws for a smooth sliding fit without play. The completed milling attachment mounts on a 3-in. length of 3/8 x 3 x 3-in. angle iron bolted to lathe cross slide in place of the compound rest as in Fig. 1. The size of this angle iron will vary depending upon the make and: model of the lathe it is to be used with. Regardless of the size of angle iron needed, first face off the two outside surfaces of the angle by clamping it on the lathe face plate with an angle block. Then cut a ¼ in. thick steel plate and rivet it to the inside surface of one leg of the angle as in Fig. 2. Again clamp the angle to the lathe face plate and bore a hole through the angle and ¼-in. plate large enough to fit on the compound mounting lug on the lathe cross slide. Clamp the angle iron to the lug in the same 122

way the compound rest was clamped, drilling and tapping needed holes in angle iron, to take the plunger pins and clamp screws used to fasten the compound rest. To drill the ½-in. milling attachment mounting hole in the angle, clamp it so that the vertical face is exactly at right angles to the lathe bed ways and bore with a drill chucked in the lathe headstock. This will place the pivot point of the attachment on the lathe centerline which is advantageous for some types of milling operations. Work to be milled is clamped against the machined surface of the slide as in Fig. 1. Use ¼ in. squarehead machine bolts with heads placed in T slots for clamping.

No. Req.

2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 1 1 14

MATERIALS LIST—MILLING ATTACHMENT All Dimensions in Inches Size and Description 3/16 x 5/8 x 4 cold rolled steel ¼ x 3/8 x 4 cold rolled steel ¼ x ½ x 3 cold rolled steel ¼ x 5/8 x 3 cold rolled steel ¼ x ¾ x 3 cold rolled steel ¼ x 1 x 3 cold rolled steel ¼ x ½ x 1¼ cold rolled steel ¼ x 3 x 5 7/8 cold rolled steel ¼ x 2¼ x 4 1/8 cold rolled steel ¼ x 1¾ x 4½ cold rolled steel 3/8 x ½ x 1 cold rolled steel 1 dia. x 2½ cold rolled steel 3/8 dia. x 8 cold rolled steel 3/8 x 3 x 3 x 3 long angle iron ¼ x 2 x 3 cold rolled steel 3/16 dia. x 7 mild steel rod for rivets 3/8 x ½ x 1¾ bronze or hard brass 1/16 x ¼ x 4½ hard brass 10-32 x 7/8 fh machine screws 10-32 x ¾ fh machine screws 6-40 x 5/8 headless flat-point socket setscrews 6-40 hex. nuts ½-20 hex. nut

JUNE,

1958

Use K H and J B A D C Q E F G M P and S 0 and R mounting angle mounting angle N L

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HIS metal-turning lathe, the

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front and rear views of which are shown in the photos above, has a capacity of diameters up to 4% in. and a maximum distance between centers of about 5% in. The tools 'required to build it are a hacksaw, breastdrill, files, clamps and a few drills, taps and dies. Assemble the legs and feet of the bed, shown in Fig. 1, and then assemble these to the top angles, with the whole in an inverted position on a good flat surface. Clamp together and drill the bolt holes through the three pieces at one time, bolt-. ing before removing the clamps. Have the holes a snug fit for the bolts. This procedure will insure the bed top being true and flat. The cone pulley and a chuck, of about %-in. capacity, can be purchased from the stores selling the small popular woodworking machines and accessories. I f you build the headstock shown in Fig. 2, it will be well to buy one of the small polishing-head spindles that are already threaded with the special thread to fit the chuck, together with a collar to fit. The spindle is .cut off to the required length.

Only a few hand tools are needed to build this lathe, the headstock itself being used for turning and drilling other parts

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Be sure that the spindle hole is parallel to the bottom surface, and ream it to fit the, spindle without shake. The washers shown should be of brass if the head is steel, and steel if the head is bronze. They may be left off until you can turn them up yourself after completing the machine. Making the head of bronze gives the .best spindle bearing. The headstock may be made of an old bearing of suitable proportions, blocking it up to the required height and fitting any available chuck to it, or it cen be made up specially from 2% by 2% %-in. piece of cold-rolled steel. An 01 hole or cup should be provided on the to1 to oil the spindle. Bolt the completed headstock to the left end of the bed with a 3h-in. bolt, 1% in. long, and a washer, and line it up with the spindle parallel to the bed slot. A good method of oheokidg this alinemenL

is indicated in Fig. 4. A straight rod, abou 1/4 in. in diameter and 10 in. long, is clamped in the chuck so that it does not show eccentricity when the spindle is revolved. A square, standing on the bed, is

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set so that it touches the rod, and the distance from the square edge to the bed slot is measured in severa1 places along its length. The alinement is true when this measurement is the same when taken at an9 place. It is a good plan to put in a couple of dowels to maintain this setting. Set up the lathe with the countershaft and motor. A general arrangement of the drive is shown in Fig. 6, together with the pulley sizes to obtain the right speeds. The motor should be at least % hp. Pulleys and countershaft are of the type used on small woodworking machines, and will cost about $3.75. V-shaped r u b b e r belts are the best, as they will not cause loss of power through slippage. T h e tailstock, in Fig. 5, is first built' up complete, but the spindle hole is not drilled until later. The dowel'sizes are not given in any of the drawings, as these can be made to suit materials at hand. To bore the tailstock, place it on the machine, with the stud nut just tight enough to prevent shake and still permit sliding forward onto the drill. A temporary screw feed is rigged up to slide the tailstock forward by clamping a piece, with a long screw in it, to the bed end with the .screw end pushing against the tailstock. Thread the spindle hole from the s ,

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in thefront end of the spindle. The taper is reamed with a %-in. drill or reamer ground to thi? required angle. The slide rest is shown in Fig. 3. The angular faces of the parts composing the dovetail slides are beveled with a file and should be smooth and flat. All the sliderest screw and dowel holes can be drilled, using the lathe and tailstock as a drillpress. The outside beveled pieces are attached to the undersides of the respective plates, and these, with the gibs and adjusting screws in place, are used as gauges for the mating inner parts. The sides of the inner dovetail parts are filed parallel, which is determined when these pieces will slide through the gauge with the same feel all the way. Blue paint will aid, used in the manner of fitting bearinge. The aosembly of the lower slide is completed fist, and the inner dovetail part of the upper, or cross, slide is fastened on at 90°, using a square to set it and omitting the dowels at this time. Complete the upper-

BENCH

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slide assembly, and, as in the case of the tailstock, the handwheels can be temporarily omitted by locking two nuts as a substitute, until the wheels can be turned up on the completed lathe. The h a 1 setting of the slides at 90' is done with the slide rest on the lathe, by feeding the cross slide across under a scriber, set up and clamped solidly to either headstock or tailstock, so that it scratches a line on the top surface of the cross-slide plate. A line is then scribed by hand on the same surface accurately at right angles to the fist. Next, with the scriber set up as an indicator on the second line, feed in the lower slide so the second line follows under the point. If the setting is correct, khe point should follow the line. Play in the screw holes should permit the

slides to be moved by light taps of a hammer, until lined up properly, after which they are doweled. The key should be filed from a piece wider than ?$ in. SO that it will fit snugly in the bed slot, and drilled

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machined table and a miter gauge for sanding the edges of work at an angle or so they are square.