Conduit Bending Test

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Gary11734

Senior Member
Location
Florida
Here's a test for your apprentices trying to bend conduit.

I learned this way, and it stuck. It is based on speed and how fast you can rough. Nobody can beat you if you can use as few steps as you can.

And, if your roughing 29 story buildings and bending thousands of feet a day, it all adds up.

If you don't care about speed, you will still learn something.


The picture shows two 1900 boxes, the distance as shown. Conduit supplied is a 10' stick. 9foot.JPG

1 - You get to take out your ruler once, and only once.

2- Measure and mark your conduit for bending and cutting. Then, put your ruler away.

3- Cut the conduit as needed.

4- Bend the conduit.


Give this test to your best apprentices. You will end up with a bunch of "oh crap" pipe laying around.

Most can't do this without pulling their ruler out two to three times. That is where the speed comes in. And, less effort after 40 years can add up.
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
My boss shook his head one time when I started an EMT bending project that required a 90 in each plane. He figured I'd have to use the pull 90's he'd bought, but I made it fit like a glove. The secret was that it was about 5 running feet and I just basically built that jungle gym from the middle and trimmed the ends to get into the boxes. It looked much more impressive than it actually was.
 

Gary11734

Senior Member
Location
Florida
My boss shook his head one time when I started an EMT bending project that required a 90 in each plane. He figured I'd have to use the pull 90's he'd bought, but I made it fit like a glove. The secret was that it was about 5 running feet and I just basically built that jungle gym from the middle and trimmed the ends to get into the boxes. It looked much more impressive than it actually was.

I learned this from the old school guys. We were using wood rulers. Open the ruler up, throw it on the floor, making all the marks and then cut. When your forty-year-old guys are beating twenty-year-olds (me), you start to figure out what the heck the old guy is doing.

I also learned to bend from the heal. I never did the take up of 5" or whatever it is to make it to the arrow for 1/2".

Those guys are gone but they knew how to bend pipe and speed was king.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
You know that the finished length of travel is 9' (assuming those are outside dimensions) so you'll need to know what the gain is for each elbow.
 

Gary11734

Senior Member
Location
Florida
You know that the finished length of travel is 9' so you'll need to know what the gain is for each elbow.

Yes, I know the "take up" for 1/2", 3/4" and 1". An apprentice should know this. I said your best apprentice. But, it won't matter. He will still screw it up! lol


If they don't know it at the time, I ask, how do you get this? They have all the resources in front of them...
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Yes, I know the "take up" for 1/2", 3/4" and 1". An apprentice should know this. I said your best apprentice. But, it won't matter. He will still screw it up! lol


If they don't know it at the time, I ask, how do you get this? They have all the resources in front of them...

This is useful in bending RMC where you may need to cut and thread the conduit before bending it.
 
So I think I am speaking for most people here that the "normal" way to do it is to bend it in two steps: Whether you use the radius deduct or the star point for each bend it doesnt matter, make one of the bends, measure the other bend, bend, cut. To do it with marking everything in the beginning, there is not enough information. You either need to do a test bend to find, or look up what the conduit length change around the 90 is, and/or distance between two opposite star point bends. I dont usually bend using those figures and do not know what they are.
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
So I think I am speaking for most people here that the "normal" way to do it is to bend it in two steps: Whether you use the radius deduct or the star point for each bend it doesnt matter, make one of the bends, measure the other bend, bend, cut. To do it with marking everything in the beginning, there is not enough information. You either need to do a test bend to find, or look up what the conduit length change around the 90 is, and/or distance between two opposite star point bends. I dont usually bend using those figures and do not know what they are.

I seem to recall that the information is usually on a label on the bender's handle. Of course, if it's been rolling around in the van for 10 years that label may be history.
 

Gary11734

Senior Member
Location
Florida
So I think I am speaking for most people here that the "normal" way to do it is to bend it in two steps: Whether you use the radius deduct or the star point for each bend it doesn't matter, make one of the bends, measure the other bend, bend, cut. To do it with marking everything in the beginning, there is not enough information. You either need to do a test bend to find, or look up what the conduit length change around the 90 is, and/or distance between two opposite star point bends. I don't usually bend using those figures and do not know what they are.


EMT is usually in "Rough" stage. So, 2-3/4" deduct should put you there. 3-1/2" for 3/4" I haven't bent a piece of EMT in twenty years, but there are some things I don't forget.

But, if you want exact measurements you can always bend a piece of a pipe and see what the "gain" is for that bender. I would always do that for rigid since each bender was a little different. I also had a personal 1/2" and 3/4" EMT bender, so it only takes one time to know the gain of that bender.

Yes, you have to know the gain, but that one piece of knowledge puts you ahead of anybody trying to out pipe you in speed.

I trained under The "shoppies" of the union. These guys were all haul butt and you better have your act together. I learned from the best. If I remember a tenth of what they trained me I would still be a pretty good electrician.
 
I seem to recall that the information is usually on a label on the bender's handle. Of course, if it's been rolling around in the van for 10 years that label may be history.

I dont believe so. The ideal benders give distance between bends and conduit shrink, thats it. Even ideal's little booklet "bender guide" does not provide this information.
 
EMT is usually in "Rough" stage. So, 2-3/4" deduct should put you there. 3-1/2" for 3/4" I haven't bent a piece of EMT in twenty years, but there are some things I don't forget.

But, if you want exact measurements you can always bend a piece of a pipe and see what the "gain" is for that bender. I would always do that for rigid since each bender was a little different. I also had a personal 1/2" and 3/4" EMT bender, so it only takes one time to know the gain of that bender.

Yes, you have to know the gain, but that one piece of knowledge puts you ahead of anybody trying to out pipe you in speed.

I trained under The "shoppies" of the union. These guys were all haul butt and you better have your act together. I learned from the best. If I remember a tenth of what they trained me I would still be a pretty good electrician.

So you are saying the 2 3/4 is the distance to the back of the bend from the star point? That is the way I would probably do it: mark the three feet for a star point bend, know that magic value and times it by two and subtract from 3 feet and thats you next star bend, then measure three feet from that and cut, then make your bends
 

rambojoe

Wireman
Location
phoenix az
Occupation
Wireman
you dont even need to make it that complicated... just (1) 90deg mark with usual take up and one 3' mark and use the b.o.b. mark... or two take up marks but that onlt works if bending on a elevated platform. and fire the guys who use sharpies!
 

Gary11734

Senior Member
Location
Florida
So you are saying the 2 3/4 is the distance to the back of the bend from the star point? That is the way I would probably do it: mark the three feet for a star point bend, know that magic value and times it by two and subtract from 3 feet and thats you next star bend, then measure three feet from that and cut, then make your bends

Ok, here is what you do;


Measure 3', draw a mark. At that mark, push the end of the ruler out to 2-3/4" (deduct) to get rid of the radius gain and mark the pipe at 3'. At the second mark, push the ruler out to 2-3/4" to get rid of the second radius gain and mark the last at 3'.

Cut the pipe. Easier to cut pipe without bends in the pipe!

Now to bend;

Site the first mark from the back of the heel of the bender and bend the pipe. (I use the heel but you could deduct for the arrow if you wish) Do the same if you still have the bender looking at "the work" end, or, turn the bender around and use the star if you don't want to be bending the pipe with another bend in front of you.

Install.
 
Ok, here is what you do;


Measure 3', draw a mark. At that mark, push the end of the ruler out to 2-3/4" (deduct) to get rid of the radius gain and mark the pipe at 3'. At the second mark, push the ruler out to 2-3/4" to get rid of the second radius gain and mark the last at 3'.

Cut the pipe. Easier to cut pipe without bends in the pipe!

Now to bend;

Site the first mark from the back of the heel of the bender and bend the pipe. (I use the heel but you could deduct for the arrow if you wish) Do the same if you still have the bender looking at "the work" end, or, turn the bender around and use the star if you don't want to be bending the pipe with another bend in front of you.

Install.

Yup, its just about knowing that "radius gain" figure. Im not sure why that isnt a "standard" way of bending......
 

rambojoe

Wireman
Location
phoenix az
Occupation
Wireman
but you have to measure first then bend, not measure - bend-measure.

that's what I mean... one end of the stick gets the arrow mark @ 2'7" from the end of the stick then off of the opposite end a mark at 3' for the bob mark... it would work out. and, you could really show up the fast union guys by not even using a tape! (with the b.o.b mark).. I never bother with the major math with the small stick, albiet still good to know. I think the triple nickel is the only auto bender ive seen with the back mark, so for the cam trac greenlee- gain and multi shot math helps... still a great way to see if a rookie is proficient. but don't give him/her a raise just yet... ya don't want them getting cocky. :)
 
that's what I mean... one end of the stick gets the arrow mark @ 2'7" from the end of the stick then off of the opposite end a mark at 3' for the bob mark... it would work out. and, you could really show up the fast union guys by not even using a tape! (with the b.o.b mark).. I never bother with the major math with the small stick, albiet still good to know. I think the triple nickel is the only auto bender ive seen with the back mark, so for the cam trac greenlee- gain and multi shot math helps... still a great way to see if a rookie is proficient. but don't give him/her a raise just yet... ya don't want them getting cocky. :)

But that radius deduct/adder figure isnt really common knowledge. I think this thread should be called "A trick to show your apprentice" not a "test"
 

Gary11734

Senior Member
Location
Florida
But that radius deduct/adder figure isnt really common knowledge. I think this thread should be called "A trick to show your apprentice" not a "test"

I learn this as it was the way to bend pipe. It is how they taught me from the start so I didn't know any other way. It wasn't a trick to me until I saw my apprentices taking out their rulers a million times. Plus, cutting the pipe without the bends is a good way to do it...

I never knew what a Benfield book was until I had to take a test!
 

rambojoe

Wireman
Location
phoenix az
Occupation
Wireman
i missed the part about pre cutting... i screwed up, sorry. however, i'd go as far as saying do not give them the dimensions, just 2 boxes with connectors installed... just to see which way is quicker. after all, getting the math is a part of the art. the cheat stick method and back to backs are pretty quick- minus killing a wireman when trying to thread the thing...
 

Gary11734

Senior Member
Location
Florida
Ok, now that we have a bunch of "Ut Oh's" on the floor, what's the best way to find the gain of what the radius is for the 1/2" EMT bender in use by said apprentices?
 
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