Electrical Conduit Bending

 

CONDUIT BENDING

Conduit bending can be learned and mastered quickly knowing a few basic formulas and techniques . Electricians that know how to bend conduit correctly rather than by trial and error set themselves apart and will save much time and energy. This Ouick-card is designed to assist electricians in the field who bend conduit with diameters of 112 to 6 . While hydraulic benders may be used with large size conduit, the same formulas and techniques will work on all sizes of conduit. This Ouick-Card references only l/Z-inch EMT in these examples for simplicity so that the electrician may practice with a length of l/Z-inch EMT and recreate these examples. A series of acronyms is used to remind the electrician of what information is needed for different kinds of bends. For example, for a 90° stub-up two things are needed: 1) Height of Stub and 2) Take-up of bender- HOST. Others are summarized as follows and will be explained later. Back-to-back bends - HOST, Offsets bends - HAMS, Segment bends - RAM, Concentric bends - RAMOO, Parallel bends - HAMOO. TYPES OF

A i ~ k e y is used for rigid conduit only. The persa n using this bender makes a senes of small bends to form the specific radius desired. This must be done carefully so as not to distort or kink the conduit while bending. ROLL-TYPE BENDER SYMBOLS ON DlFFERENT HEADS

Arrow

MEASUREMENT

I

3-point Saddle

Back to Back

Tear Drop

Star

Notches on Boltom of Shoe

B Mark

A  Mark

TYPICAL MARKINGS ON A CONOUIT BENOER Foot Pedal

I Arrow : lor 90 °stubs, offset bends, and the outer marks 01 a

X

BACK·TO-BACK

E X

Hook

I

Star-point: lor back-to-back

Tear Drop (Rim notch): for the center mark 01 a 3-point saddle (exact center 01 45 ° bend)

Degree scale: for offsets , saddles , and special situations

bends

TYPES OF BENDS

think ARROW bend. This is the most common type of bend the electrician will make . Stub-ups use the arrow mark on the bender.

C\lA 1  7 I S :1 12

:1

Another common type of bend that electnclans make IS the back -to-back bend . A backt o - ~ a c k bend IS slmply two 90 b e n d s s ~ a c e d apart formmg a U shape. Wlde back-to-back bends use the star mark on the bender. Close back-to back bends use the arrow mark on the bender. EXAMPLE 2: think STAR Wide back-to-back bends. Make a back-to-back bend with ab 16  stub anbd a 24 span etween stu S. Ke Point ___ 2nd bend ___ y reverses dlrectlon of bender by facmg the opposite end from whlch you measured (Y) and use star mark. To make backto-back bends two thlngs are needed:

CONDUIT TYPE/SIZE

EMT EMT W RIGID 3/4

TAKE-UP/

Deduct

Bendlng Posltlon Symbols

5

X- bend

6 

ake-up is the distance in 1  EMT 8 inches that the actual 3f4 RIGID curve of the bender takes l 1f4 EMT up .  11   l   RIGID It is the amount of inches from the arrow mark on Take-up in inches is the bender to the backside subtracted from the of the conduit after the 90 length of the stub to be made . degrees bend is made.

y - bend

Aln

vrv

X

reverse bender

o

Remember H O S T Height Of Stub 2. Take-up of bender

~

.. ¡

STUB

Y

1.

fL

Make the bend foliowing the technique from Example 1.

MEASURING

BENO 2

Wide Bend

THE

CONDUIT

RESULT

B ~

16]]  16 1   1 5  16   16

o

Step 4: Measure 24   from the back of the stub you just made. BENO 2-Bendlng the candult Using one half stick, bend a Step 5: Reverse the bender 16  90 0stub-up. Measure 16 so that the hook faces the from the end of the conduit opposite end of the conduit and subtract 5 for take-up. (Y). Slide the conduit into 16  _5  = 11 . Step 2: Mark the conduit at the hook so that the star mark is aligned with your 11   from (X) with a fine point 24 measurement. Make permanent marker completely sure that each bend is l' d . around the conduit. BENO 1 B di th d It a Igne wlth each other. - en ng e. can u Make the bend foliowlng Step 3: Lay the condUlt on a hard the technique from Example 1 surface and slide the conduit RESULT' One 16 stub-up . through the hook of the shoe 24 between 251f4 opposite ' until the arrow mark is aligned stub-up. wlth your measurement 11   The foliowing diagrams iliusfrom the end of the conduit (X). trate positions of bender . MEASURlNG THE CONDUIT Step 1 ; Use a 10 foot stick of 112 EMT and cut it in half.

2sW  

24 

Y

EXAMPLE3: - think ARROW Close back to back bends. Make a back-to-back bend with two 20 112 stub-ups and 24 between stub-ups. Key Point - - - 2nd bend -   same bender direction as first stub-up, subtract take -up , and use the arrow mark.

24  

BENO 1- Bending tlle candu candultlt STEP 3: Lay the conduit on a hard surlace and slide the conduit through the hook 01 the shoe

STEP 5: Keep bender in the same direction of the first stubup , hook of the bender facing stub-up . until the arrow mark is aligned Slide the conduit through the hook 01 the shoe until with your 15 112 measurement. the arrow mark is aligned Make the bend foliowing the with your 19 measurement. technique from Example 1. sure that each bend is Make MEASURING THE CONDUIT STEP 1; Using the other hall stick MEASURlNG THE CONDUIT aligned with each other. of EMT, bend a 20 112 90 ° stub  STEP 4: Measure 24 from the Make the bend foliowing the technique from Example 1. up. Measure 20112 deduct 5 back of the stub you just made. Result: One 20112 stub -up, take-up. 20112 - 5  = 15112 . Oeduct take-up. 24 - 5  = 19  . 24  between , 20W ' STEP 2: Mark the conduit at Yo Mark the conduit at 19 . with a marker completely opposite stub -up. 2- Bendlng the canduit BENO around the conduit.  

BENO 1 Bend 1 Close Arro w Bend

X- flip or rev erse bende r y -flip or or

Bend 1 Arrow

RESULT

Arrow

12  (STUB LENGTH) y

Backto-to Back

Step 4: Holding the bender with one hand , place one foot on the conduit and one foot on the foot pedal. Bend the conduit up to the 90 ° mark on the side of the bender , exerting constant pressure on the foot pedal throughout the full bend . The foliowlng dlagrams lliustrate the steps.

Bend 1

BENO 1

3-point saddle

90 °   STUB UP UP

S

is aligned with the arrow mark on the bender.

POSITION OF BENOER

(Pencil Mark)

BENDERS

A Roll-type - is most commonly used for bending EMT sizes 112 -1114 . These benders have two parts, the handle and the shoe of the bender. The shoe has markings on it that are used for different kinds of bends and markings to measure the angels of bends.

90°° stulrup 90

EXAMPI..E 1: Step 2: Mark the conduit at Make a 12 stub-up. The end 7  from the end of the of the conduit should be 12   conduit (X) with a fine in height after the bend is point permanent marker made. To make a 90 ° stub up two things are needed: completely around the Remember HOST conduit. 1. Height of Stub BENDlNG THE CONDUIT 2. Take -up of bender Step 3: Lay the bender and MEASURlNG THE CONDUIT conduit on a hard surface . Step 1: Use 112 EMT. Measure With the hook of the bender 12 from the end of the and yourself facing the end conduit and subtract take -up you measured from (X) , slide in inches for 112 EMT. the conduit into the hook of the shoe until the pencil mark at 7 . 12 - 5 = 7 .

F;; : ?f ,  X

20V,

Y

BENO 2

RESULT

9

W 24  

reserved.  

OFFSET BENDS bends.

- Think ARROW

For numbers 1 and 2 use these standards as a guide: For offsets 5 inches or more use a 45 ° or 60 ° bends. For offsets of 3 or 4 inches use 30 ° bends. For offsets of 2 inches in depth use 22112° bends. For small offsets of 1 inch or less use 10 ° bends. For numbers 3 and 4 use OFFSET TABLE.

An offset bend is another commonly used bend made by electricians.

These bends are made to avoid objects such as other conduits or to make changes in elevation.

However both the angle and the height of the offset use up so me lengt h of condun.

per in eh

MEASURING THE CONDUrr MEASURING STEP 1: Use 10 ft 01 W' .

per n eh

Depth 01 offset x Multiplier

Distanee between bends Angle

If the offset is heading away from the object, the sh rinkage can be ignored. To make an offset bend four things are needed. Remember HAMS 1. Height of object 2. Angle of bend 3. Multiplier 4. Shrinkage per inch of rise.

~ ~

Shrinkage Per Ineh 01 Rise

To make an olfset bend lour things are needed. Remember HAMS 1. Height 01 object 5'h 2. Angle 45 ° 3. Multiplier 1.4 4. Shrinkagejinch of rise 3s

OFFSET FORMULA TABLE

This is called shrinkage and this amount must be added to the measurement if you are heading toward the object.

u ~ i e r o f

Offset Ilepth

10 °x 10 °

6

1 116

22'12 °x 22'12 °

2.6

3/16

30 °x 30 °

2

1f4 per in eh

45 °x 45 °

1.4

3/ 8  per ineh

60 °x 60 °

1.2

W ' per ineh

: : = ~ : ; ; ;

EXAMPLE5: 45-degrees offset bend. Make a 45 ° offset around an object that is 5'12" in height and 24  lram the end 01 the condu it.

~ ~ : " " - - : : : : - - - : : - - ~ : = . = : : = = ; = = = = = , = = = , = = = = : : : : : = ~ EXAMPLE 4: Therefore , 3 (he ight of opposite end ofthe conduit M·

Note that he object is 24 lrom the end of the conduit. STEP 2: Find the lirs lirstt bend . Using the Table above find the shrinkage per ¡neh of rise of the condu it. Since the offset is heading toward the object , this amount must be added to 24 . From the Tab le find the ang le ofthe offset 45 0. The shrinkage 0145 ° is equa l to

3/ e

per inch of object height. hard surface. The hook ofthe Therefore 5112 (height of object) bender should face the opposite end ofthe conduit M. Now slide x 3/ 2;/ and 24  + 21 16   2 ~ 1 / 16 16 the conduit through the hook Now measure and mark 261 16   until the anow is aligned with lrom the end 01 the conduit (X). th e ir51 bend mark at 26 1/ 1  . From the fioor bend a 45 o angle.

,45' Offset

Bend 1 Arrow

Bend2 Arrow y

X X 185/,6 

26

1

7% J

1/   ,6

y

1

18s/'6

I

?3Jr1 ?3Jr 1

26 1/ 1 6

STEP 3: Find the second bend. Using the Offset Formula Table find the offset m u ~ i p l i e r 01 the

STEP 5: Next stand the conduit hand le on the floor with the hook 51ill facing the

45 and multiply it by the ° angle height of the object. Therelore 14 x 5W' = 7% Now e ~ u ~ and mark 7% from

opposite side 01 the conduit. Slide the conduit through the hook 01 the bend er until the arrow is aligned with the second bend mark. Make a 45 ° bend by bending the conduit down with ann/ hand pressure.

1 t mark, mark back toward ° 30 offset ben d. object) x 114' = % and Now slide the conduit through the end 01 the conduit (Xl. 18  + 3f4 = 18% 18%   Now Make a 30 ° f f ~ e t around an the hook until the arrow is BENDlNG THE CONDUIT ob¡,ect that IS 3 In helght and measure and mark 18 %   aligned with th e first bend 4: Lay the conduit on a STEP 18 from th e end of the condul t. from the end of the conduit (Xl mark at 18% . From the floor . To make an offset bend fourthlngs bend a 30 ° angle. are needed . 30 °Offset Bend 1 RESULT FOR EXAMPLE 4 RESULT FOR EXAMPLE S Remember HAMS Arrow Bend 2 ~ h l o f ~ 2. Angle of bend 30 ° x 1st Bend A /\JI ' Y I 3. Multip'lier 2 -¡;;;-¡ ; ; ' : ; : : ; : : ~~ ~ ~ / .. 4. Shrinkage/inch of rise % 12% 12 % 6  MEASURING THE CONDUIT 18% 18 % x 18% y TEP 1: Use 10ft ofl12 EMT . _ 3  and cut it in hall. Note that STEP 3: Flnd the seco nd bend . 2nd Bend 6 the objects is 18 from the end USlng the Table above flnd STEP 5: Nfro stand the bender's X B 6'_X   -/ ; 300 ~ .._ _ _ X of the conduit. the offset multlpller of the 30 ° handle on the floor wlth the ~ ~   ~ ~ ~ STEP 2: Find the first bend . angle and multlply it by the hook still facing the opposite l·' 18 'I ' 1 I' 24   Using the Table. abolle i ~ d the height of the object. side of the conduit . Slide the shnnl