# bending question, concentric bends...



## kbsparky (Sep 20, 2007)

Do you want instructions on how to do this, or a thesaurus on how to describe it?


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## littlebro (May 19, 2011)

If you're not running too many and your spacing is right, you can use the next size bender. I've run 3 1/2" using 1/2" for the first, 3/4" for the second and 1" for the third. The 1" smashed the pipe a little the first time, so maybe I just got lucky! It's a lot easier than doing it the real way, especially for those of us who don't do it every day-


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## K2500 (Mar 21, 2009)

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


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## Rockyd (Apr 22, 2007)

littlebro said:


> If you're not running too many and your spacing is right, you can use the next size bender. I've run 3 1/2" using 1/2" for the first, 3/4" for the second and 1" for the third. The 1" smashed the pipe a little the first time, so maybe I just got lucky! It's a lot easier than doing it the real way, especially for those of us who don't do it every day-


If you have a welder's crayon, (you can swing an arc by holding one end of your tape measure to establish the radius size) and in a place that doesn't matter, mark the floor up to know what sizes to bend. It also allows you to "see" where to fix "bad" spots on your bends:jester::thumbsup:


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## don_resqcapt19 (Jul 18, 2010)

The radius has to increase for each bend by 1/2 of the OD of each of the condiuts plus the conduit spacing. I have never done it for thinwall, but back when labor was a lot cheaper we did a lot of it for rigid. We would use 18 shots at 5° each to get the 90. The radius divided by 1.57 would give you the "developed length". That would be divided out in equal spaces for the 5° shots. Often we would use a strip of dressmakers elastic and put our 18 marks on that and then just strech it along the conduit and put our marks on the conduit. No need to divide and measure fractions.

Now with rigid, as long as the largerst conduit is 2" or less, we bend all of the conduits on the same shoe no matter what size, but you can't make that trick work with EMT.


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## piperunner (Aug 22, 2009)

Well if you bending long sweeps on smaller conduit its the same process that you use when bending large conduit nothing different .

Greenlee has a calculator for segment bending handpocket type if your just starting out .


On small conduit if we need to bend around a tank or need a long sweep we use segment shoe layout the shots with less than 3 deg per shot the shots are what ever your total needs to be of your angle of bent degree total .

Expample only- 90 deg bend by example only 9 shots of 10 degrees for each shot than you figure length needed we do this by actual field bending with different shoes the stuff you here on this forum doesnt work thats out of a book .

But you must be always less than 5 deg but 3 is better so one thing you need is a bender that can bend segment bends .

You can use a larger shoe but it looks like crap bottom line there is no easy way to explain this on a forum pm me if you need more help.

Before we had books in the trade and electrician forums we bent conduit and made our own formulas with each actual hand bender or electric bender or hydraulic types from a 90 stub you can find take up deduct and if you bend it one degree at a time it will give you what the book calculator gives you for each conduit size .

For each degree of shots you make the bend in the conduit wall moves at a set length to the angle the more shots of less degrees the more length you get . the less shots of more degrees the shorter the length of moves and the angle to length results made is less .

You need to figure out that degree to shots to length once you have that every conduit big or small its all the same .


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## sparky970 (Mar 19, 2008)

don_resqcapt19 said:


> The radius has to increase for each bend by 1/2 of the OD of each of the condiuts plus the conduit spacing. I have never done it for thinwall, but back when labor was a lot cheaper we did a lot of it for rigid. We would use 18 shots at 5° each to get the 90. The radius divided by 1.57 would give you the "developed length". That would be divided out in equal spaces for the 5° shots. Often we would use a strip of dressmakers elastic and put our 18 marks on that and then just strech it along the conduit and put our marks on the conduit. No need to divide and measure fractions.
> 
> Now with rigid, as long as the largerst conduit is 2" or less, we bend all of the conduits on the same shoe no matter what size, but you can't make that trick work with EMT.


You actually "multiply" the radius by 1.57 to get D.L. I also like to use 2 2.5 deg bends at the start and end.


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## tates1882 (Sep 3, 2010)

Zaped said:


> For small EMT conduit, where online would I find some technique description for bending a bunch of 90's in the same plane (i.e., mulitple adjacent pipes all with a 90 degree bend at same place. Called concentric bends I think. ). Thanks.


Well I take the first 90's measurement add the spacing plus the od of the pipe and that gives me the measurement for the next 90 then add spacing and od of the next pipe for the next 90. I use 7/8" for 1/2" emt, 1 1/8" for 3/4" and 1 3/8 for 1". http://www.electriciantalk.com/members/tates1882-14731/albums/work/1434-rocket7-1.jpg Thats how I bent all the 1" in the link above.:thumbsup:


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## don_resqcapt19 (Jul 18, 2010)

sparky970 said:


> You actually "multiply" the radius by 1.57 to get D.L. I also like to use 2 2.5 deg bends at the start and end.


Thanks....


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## BBQ (Nov 16, 2010)

don_resqcapt19 said:


> Often we would use a strip of dressmakers elastic and put our 18 marks on that and then just stretch it along the conduit and put our marks on the conduit.


Sweet!


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## Rockyd (Apr 22, 2007)

don_resqcapt19 said:


> The radius has to increase for each bend by 1/2 of the OD of each of the condiuts plus the conduit spacing. I have never done it for thinwall, but back when labor was a lot cheaper we did a lot of it for rigid. We would use 18 shots at 5° each to get the 90. The radius divided by 1.57 would give you the "developed length". That would be divided out in equal spaces for the 5° shots. Often *we would use a strip of dressmakers elastic* and put our 18 marks on that and then just strech it along the conduit and put our marks on the conduit. No need to divide and measure fractions.
> 
> Now with rigid, as long as the largerst conduit is 2" or less, we bend all of the conduits on the same shoe no matter what size, but you can't make that trick work with EMT.


Gets even easier than that, do you fish?

Go to Fred Meyers, sears, wally-world, where they sell tackle. In the sinker section, they have *six foot long surgical tubing*, Best stuff ever for doing "fast" marking of pipe for the bender. Buy several. that way, you can have them set up for the number of shots necessary. works great!

Shouldn't take that much longer to crank out concentrics, than normal if you have a chain vise on the slider ...


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## macmikeman (Jan 23, 2007)

Here is a trick to modernize the whole operation. Get a large envelope. Put several one hundred dollar bills in it. Write the word Inspector on the front of the envelope. Run just one two inch conduit and pull many many wires thru the pipe and forget to do any sort of derating or conduit fill calculation. 
:jester:


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