1173B Wax Machinable Make Your Own

Make Your Own

MACHINABLE WAX Anyone can get machineable wax; simply chuck up a candle! But it doesn’t machine really well. This is because the wax needs to be kept really cold in order to machine it at all. What is needed is a much firmer type of wax. You can purchase it from many (US) suppliers: but, since it is so easy to make, who (in his or her right mind) would want to pay for the stuff? and import it? (I found no Australian suppliers). You can make your own! What you need is: A suitable mold……………………..– ideal is a box lined with paper or foil. The paper makes it easier to get the block of wax out of the mold. Don’t use polythene containers as there is a risk they’ll melt or dissolve! A candy thermometer……………...- or IR non-contact thermometer a pot…………………………….…...- big enough for the quantity you are going to make 4 parts by weight of parafin wax….- (candle wax) - coloured wax may be good or use col oured plastic. The colouring will make it easier to see what you’re doing when machining. 1 part by weight of polythene film..– (cut into strips) Melt the wax. You need it to get good and hot – about 275 degrees F (135C) or greater. It won’t get there if you use a double boiler (water boils at 212F (100C) so that’s the limit with a double boiler), so heat it directly on a low setting. Take care. Wax is flammable (like why else would it get used in candles?) and the flash point of 301C says “TAKE CARE!”. Use a candy thermometer or infra-red non-contact thermometer. When it gets up there, drop in a couple of strips of polythene film and stir to dissolve them. They will dissolve quite slowly. Keep adding polythene and keep stirring until no more polythene will dissolve. You can allow the temperature to increase to an ABSOLUTE MAXIMUM of 200C as you dissolve more and more polythene. The more polythene gets dissolved, the thicker the product becomes – it will take on a consistency like thick, smooth custard. When no more plastic will dissolve, scoop out any undissolved plastic, pour the wax into your molds, and allow to set. In my trials of this stuff, I found that when it is set and cool. it has a density of around 0.9 grams per cubic centimetre – just a little lighter than water – sorta like an iceberg. This means it’s easy to estimate how much to make to fill your molds. Actually, you should make maybe 5% more to allow for shrinkage as it cools. The wax machines cleanly in the mill, with a good finish. Very little wax becomes stuck on the cutter and there is no evidence that the wax melts as it is cut. I used a 10mm end mill at about 200 rpm, and no coolant. Higher speeds should be OK.

The following data have been gleaned from a number of (US) suppliers web sites. The info supplied on those websites is so consistent you might even think that they have all copied from each other!

Hardness: Specific gravity: Flash Point of: Softening point: Volumetric shrinkage at room temperature:

50-55 (Shore “D” scale) .92 575°F/ 301.7°C 226°F/ 107.8°C 7%

Contains No Class 1 Ozone Depleting Chemicals! Does not produce hard edge chips. Non-toxic. Self-lubricating, non-abrasive and will not fuse when machined at high-end spindle rpm’s and feed rates. May be remelted, recast and machined again without any loss of original properties. Will not gum up on tool bits. Drill & Ream It Saw Or Carve It Mill It Thread It Assemble It & Check Dimension Turn It Chamfer It The following prices came from one supplier, but seem to be typical: 3"W x 7"L x 1.5"H Rectangular Block 3"W x 7"L x 3"H Rectangular Block 5"W x 10"L x 3"H Rectangular Block 6"W x 12"L x 3"H Rectangular Block 24"W x 24"L x 2"H Rectangular Block 2" Dia. x 12" Cylinder 3" Dia. x 12" Cylinder 4" Dia. x 14" Cylinder 6" Dia. x 18" Cylinder 1.5" Dia. x 12" Cylinder

$13.50 $22.55 $52.90 $66.26 $337.80 $11.25 $30.45 $48.10 $145.80 $10.15

MORE ON MACHINABLE WAX Well, this time I started with a kilo of wax (my first experiment started with 150 grams!). After it was melted, I started mixing in some plastic garbage bags, and just kept going until no more would dissolve (photo 1). I haven’t weighed the total product yet, but I guess there’s somewhere be1 tween 150-250grams of plastic dissolved. On the way, I discovered that not all bags are polythene...one (GLAD) garbage bag which looked sorta the same simply shrank to about 10% of its original size. There may, of course, be a 2 good use for shrinking bags – I’ll try one as shrink wrap and let you know… With the original lot, I simply poured the mixture into a cardboard box mold with the result that undissolved polythene more or less sank to 3 the bottom while the mixture set. This time, I was a bit more cunning,,,I strained the mixture through a metal kitchen strainer as I poured it into the mold (a tefflon coated cake pan). The cold block just fell out of the pan when I turned it over

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Now, if you think you might make more machinable wax, you should simply dump the strained residue back into the melting pot – it will dissolve when you add more wax (waste not, want not!).

As you can see, there’s plenty of shrinkage (photo 4). The cake pan holds about 1600 ml. The shrinkge was measured by filling the depression with water – about 200 ml, so, about 12.5% shrinkage from about 185oC – about 8 parts in 10,000 per oC. If I had allowed the mixture to cool by (say) 50oC before pouring, there would have been much less shrinkage in the mold.

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The straining worked! No ‘fungoid’ patches in the bottom of the mold (photo 5) as I had with the first lot.

POLYTHENE Polythene http://en.wikipedia.org/wiki/Polyethylene Polyethylene (abbreviated PE) or polythene (IUPAC name polyethene or poly (methylene)) is the most common plastic. The annual global production is approximately 80 million tonnes. Its primary use is in packaging (plastic bag, plastic films, geomembranes, containers including bottles, etc.). Many kinds of polyethylene are known, with most having the chemical formula (C2H4)nH2. Thus PE is usually a mixture of similar organic compounds that differ in terms of the value of n. Physical properties Polyethylene is a thermoplastic polymer consisting of long hydrocarbon chains. Depending on the crystallinity and molecular weight, a melting point and glass transition may or may not be observable. The temperature at which these occur varies strongly with the type of polyethylene. For common commercial grades of medium- and high-density polyethylene the melting point is typically in the range 120 to 180 °C (248 to 356 °F). The melting point for average, commercial, low-density polyethylene is typically 105 to 115 °C (221 to 239 °F). Chemical properties Most LDPE, MDPE, and HDPE grades have excellent chemical resistance, meaning that it is not attacked by strong acids or strong bases. It is also resistant to gentle oxidants and reducing agents. Polyethylene burns slowly with a blue flame having a yellow tip and gives off an odour of paraffin. The material continues burning on removal of the flame source and produces a drip.[3] Crystalline samples do not dissolve at room temperature. Polyethylene (other than cross-linked polyethylene) usually can be dissolved at elevated temperatures in aromatic hydrocarbons such as toluene or xylene, or in chlorinated solvents such as trichloroethane or trichlorobenzene. Plastic bags, buckets, soap dispenser bottles, plastic tubes

Plastic bottles, plastic bags, trash cans, imitation wood

The author suggests polythene film which usually comes as plastic bags or films thin and easy to melt check the symbol. Not sure search polythene film or polythene bags to see what's available.