# Does anyone know the formula for concentric offset bends



## lewis hinkle (Aug 19, 2007)

Hi: Does anyone know the formula for concentric offset bends and setup for
3" IMC??

Regards,

Lewis


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## RIVETER (Sep 26, 2009)

Have not done it for many years. Just GOOGLE it...but I suspect you already have, right?


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## lewis hinkle (Aug 19, 2007)

*Concentric offset*

Google has nothing:no:


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## nolabama (Oct 3, 2007)

I thought it was concentric ninetys. Here goes nothing. If the cosecant of the angle times the off set desired is equal to the distance between the centers of the bends , would you not add the od of the pipe plus spacing to give you the new offset size? This will then give you what your new angles will be, but since everyone uses thirty cause its two, your gonna have a funny multipier and mess the math up, bend one a bit more than it should be, back up and look at how effed up it is, throw it away and start over......I never could bend pipe real well.


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## CoopElec (May 16, 2011)

*example*

3" x 42" stub , 24" radius 

1.57 x 24" radius , = 37.68"
start mark = 42" - 24" - 3.5" for outside of pipe. = 14.5"
make mark at 14.5"
divide 37.68 by 20 = 1 7/8 "
make 20 marks on pipe after the 14.5" mark
set bender at second mark on pipe
bend 4.5 degrees for 20 marks
adjust accordingly for different radii


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## nolabama (Oct 3, 2007)

CoopElec said:


> 3" x 42" stub , 24" radius
> 
> 1.57 x 24" radius , = 37.68"
> start mark = 42" - 24" - 3.5" for outside of pipe. = 14.5"
> ...



Isnt that a ninety?


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## CoopElec (May 16, 2011)

*90*

Yes, I misread the post and got side tracked. segmented off sets are to much work.


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## IBEWRockstar (Nov 10, 2011)

lewis hinkle said:


> Hi: Does anyone know the formula for concentric offset bends and setup for
> 3" IMC??
> 
> Regards,
> ...


Someone is going to pay you for concentric offsets?


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## wwilson174 (Apr 25, 2008)

lewis hinkle said:


> Hi: Does anyone know the formula for concentric offset bends and setup for
> 3" IMC??
> 
> Regards,
> ...


The term "concentric" is applicable to circles or segments thereof. Do you perhaps mean parallel offsets?


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## rexowner (Apr 12, 2008)

Don't think I have done any concentric offsets.

Do you mean parallel offsets? Like how much further down to start
the next offset.


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## rexowner (Apr 12, 2008)

If you want the conduits distance "D" apart (center-to-center).

Start the bend of the next conduit:
D x tangent (degree of bend / 2)
later.

I don't think the size of the conduit or radius of the bender enters into it.

I got this from Coffman's Method of Conduit Bending, by Ronald
S. Coffman.


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## CoopElec (May 16, 2011)

http://www.powells.com/biblio/1-2221114612303-2


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## nolabama (Oct 3, 2007)

So I have dug out my benfield bender book and blew the dust off of it. Nada on the concentric offsets. Nothing in the ugly book either.


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## rexowner (Apr 12, 2008)

CoopElec said:


> http://www.powells.com/biblio/1-2221114612303-2


I agree this is a good book. It is easier to follow than Coffman's.
I couldn't find my copy. I would second your suggestion as a
really good resource.

Coffman's is a good source if you want to do calculations that take the radius
of the conduit and bender into account but the math is somewhat hard to
follow.


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## CoopElec (May 16, 2011)

*Old School*

I learned the old school way. From old timers. Then I got the book. 
I remember reading a couple of post awhile back about the elastic band.
Laugh, but it works. Have No-Dawg will travel.


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## wick19 (Apr 8, 2011)

http://www.porcupinepress.com/_bending/Concentric.htm

Lots of good bending info here. Hover your mouse over the gray bar on the left and you get more options/info.


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## sparky970 (Mar 19, 2008)




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## 220/221 (Sep 25, 2007)

Wouldn't concentric *offsets *all be the same???


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## Service Call (Jul 9, 2011)

Cut a factory 90 in half and add 4 couplings, voila, two offsets.


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## Service Call (Jul 9, 2011)

My bad. You said IMC. I though it was EMT. Sorry


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## aDudeInPhx (Feb 20, 2012)

wxyz


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## ptcrtn (Mar 14, 2011)

http://www.porcupinepress.com/_bending/ParallelBends.htm


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## bgleason (Mar 3, 2012)

There is an android app for conduit bending that is awesome.


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