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01-20-2009, 05:53 PM   #1
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## Conduit Bend Calculation Help

I tried to make a 30° offset bend with 1/2” conduit between floor joists the distance from face of joist to face of joist is 14 5/8”. I used 14 5/8” x 2 for a 29 ¼” center to center bend. I lined up each mark with the arrow on my Greenlee Bender. I ended up over bending using the 29 ¼ centers where did I go wrong?

Last edited by johnny5; 01-20-2009 at 06:07 PM.

01-20-2009, 06:10 PM   #2

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Are you bending an offset bend? I'm picturing you to be running parallel to a joist and then wanting the conduit to run 30 degrees over to the other joist then continuing parallel to it.

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01-20-2009, 06:19 PM   #3
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Quote:
 Originally Posted by johnny5 I tried to make a 30° offset bend with 1/2” conduit between floor joists the distance from face of joist to face of joist is 14 5/8”. I used 14 5/8” x 2 for a 29 ¼” center to center bend. I lined up each mark with the arrow on my Greenlee Bender. I ended up over bending using the 29 ¼ centers where did I go wrong?
It's off by the diameter of the pipe. Think about it. Set the pipe on the floor so that the offset is vertical. The 14-5/8"" is from the floor to BOTTOM of the upper part of the offset. But you need 14-5/8" to the TOP of the upper part. SO... the depth of the offset must take that into account, and you must subtract the diameter of the pipe from the measurement.

14-5/8 - diameter = depth
depth x 2 = distance between marks

Also, be sure that you bend both marks with the bender in the same orientation.

 01-20-2009, 06:21 PM #4 Newbie   Join Date: Oct 2008 Posts: 4 Rewards Points: 10 Yes, Stubbie am trying to bend a 30° offset from joist to joist. Don't want to trash another piece of conduit would appreicate any expertise.
 01-20-2009, 06:40 PM #5 Newbie   Join Date: Oct 2008 Posts: 4 Rewards Points: 10 Thanks InPhase277, I did think about subtracting the 1/2" pipe daimeter roughly 3/4" to make my bend but needed to here it from someome with a bit more experiance would rather not trash another length. Thanks again
 01-20-2009, 06:49 PM #6 UAW SKILLED TRADES     Join Date: Jan 2007 Location: Kansas Posts: 5,341 Rewards Points: 2,652 Inphase nailed it.... your distance between bends is 2 x 13 7/8 or 27 3/4". 13 7/8" is your offset height. Shrinkage is 3 3/8". __________________ " One nice thing about the NEC articles ... you have lots of choices" Stubbie
 01-20-2009, 08:29 PM #7 Licensed electrician   Join Date: Sep 2007 Location: Maryland Posts: 10,861 Rewards Points: 1,876 You could still use the piece that is too long if you just allow it to roll uphill slightly. This will eat up the extra depth of the offset.
 01-20-2009, 09:34 PM #8 Electrician   Join Date: Nov 2005 Location: Winnipeg, Manitoba Posts: 1,298 Rewards Points: 802 Are you wanting to make more then one of these bends and make them all match? If your not why don't you just put a little more bend in or a little less to make it fit, it won't be a perfect 30 degree bend but no one will notice if there is only one.
 01-20-2009, 09:41 PM #9 You talking to me?     Join Date: Dec 2007 Location: sw mi Posts: 7,551 Rewards Points: 6,290 I'm with Darren on this one. Unless you are trying to match an existing pipe, I would simply take a little of the bend out. It won;t be much since you are talking 3/4 of an inch less offset.. With 1/2" you can simply place the pipe on the floor with the offset standing up and pushing gently on the angled part to straighten it just a wee bit. Do that to both bends equally. Then take the bender handle and lay the short part of the pipe against the handle and compare the other end of the pipe to the handle to make sure it is parallel to the shorter part.
01-20-2009, 10:35 PM   #10
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Nope just going to bend the one pipe will try your method of salvaging before I try to bend another.

Thanks for all the input.

Last edited by johnny5; 01-21-2009 at 08:16 PM.

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