Bending EMT Back to Back 90 bends

[Valencia Instructor]

While teaching my students the method of bending back to back 90, utilizing the subtraction of the take up and using the arrow for the first bend. And then measuring the span and utilizing the star for the second bend, a student asked me why we do not just use the star all the time?

Looking for an answer?

Thanks to all you " Sparkys"

 

[infinity]

You can use any point on the bender as long as you adjust your standard 90° deduction. I typically use the front of the bender on the mark on the EMT.

 

[kwired]

While teaching my students the method of bending back to back 90, utilizing the subtraction of the take up and using the arrow for the first bend. And then measuring the span and utilizing the star for the second bend, a student asked me why we do not just use the star all the time?

Looking for an answer?

Thanks to all you " Sparkys"

The star is the "back of the bend" as measured from "back side" of the bending shoe.

The arrow is the "take up" that gets added to remaining distance to end of a stub measured from "front side" of bending shoe.

Neither is same dimension from either end of the shoe.

If you had a mark that was at center of a 90 degree bend I suppose that would work either way along with knowing some sort of "take up" figure associated with that mark.

 

[kwired]

You can use any point on the bender as long as you adjust your standard 90° deduction. I typically use the front of the bender on the mark on the EMT.

Turning the bender shoe the other way around for the second bend is a different approach on how to measure, add/deduct/etc. than keeping the bender shoe oriented toward same end of pipe you are bending. But turning it the other way is much easier leverage wise if the second bend is near the "other end" of the pipe.

 

[infinity]

Turning the bender shoe the other way around for the second bend is a different approach on how to measure, add/deduct/etc. than keeping the bender shoe oriented toward same end of pipe you are bending.

I was responding to his question about not using the star all of the time which you can do by adjusting your deduction.

I agree that depending on the distance between the back to back bends turning the bender around is at times the easier way to go. For the most part you can just add 1/2 of the bender deduction and turn the bend around.

 

[acrwc10]

Half the jobs I see, the electrician has used a hacksaw and a coupling to get the correct length.

 

[LarryFine]

Half the jobs I see, the electrician has used a hacksaw and a coupling to get the correct length.

Hacksaw for a hack-job?

 

[infinity]

Thankfully I haven't had to cut EMT with a hacksaw in over a decade. My elbow is grateful that we have power tools.

 

[Valencia Instructor]

Thank you all for your inputs. I was hoping for a logical answer to my question. Why do we not just use the star all the time, while bending EMT?

 

[infinity]

I was hoping for a logical answer to my question. Why do we not just use the star all the time, while bending EMT?

Did you get the answer?

 

[jim dungar]

Did you get the answer?

See post #2.

When bent, conduit has an 'inside' and an 'outside' due to the thickness of the conduit.
The two different bender marks relate to these two different dimensions, in an effort to reduce the math. You make your field measurement and add or subtract the conduit thickness or simply use the appropriate bender mark.

 

[Valencia Instructor]

See post #2.

When bent, conduit has an 'inside' and an 'outside' due to the thickness of the conduit.
The two different bender marks relate to these two different dimensions, in an effort to reduce the math. You make your field measurement and add or subtract the conduit thickness or simply use the appropriate bender mark.

Okay?

Did you get the answer?

not yet???

 

[rambojoe]

Okay?

not yet???

Are you instructing with benders and pipe or just on paper?

 

[Valencia Instructor]

We do both. The question still remains. When using the arrow, we subtract the rise. When we bend a back to back we utilize one mark and the star. I suppose we could make the second bend by subtracting the rise and using the arrow. So why don't we just use the star all the time?

 

[jim dungar]

We do both. The question still remains. When using the arrow, we subtract the rise. When we bend a back to back we utilize one mark and the star. I suppose we could make the second bend by subtracting the rise and using the arrow. So why don't we just use the star all the time?

There is no law against using the same mark all the time. It is up to you, and the amount of math you want to do.

 

[rambojoe]

We do both. The question still remains. When using the arrow, we subtract the rise. When we bend a back to back we utilize one mark and the star. I suppose we could make the second bend by subtracting the rise and using the arrow. So why don't we just use the star all the time?

You can.
Dont call it a rise, it is a °90 stub, made w/out cutting. Sweet, right?!
A back to back, while it seems similar- is best distinguished from making a "back of the °90" bend. Which in turn is best to learn it, a specific length 90 stub or a specific "back of a 90"...
The reason for not always using arrow or star is sooner or later the bender handle gets in the way, say a b. to b. bend at 2' w/ 2' stubs...
The point is to cut less, and use the easiest math/mark and bender to pipe floor leverage...
Try it is my point. Too many people get turned around bending pipe, including having the bender turned around.
Master stub ups (-) master back of 90's, master offsets and then center bends..

Ive also found in teaching, if a student asks why- wether you know the answer or not... well, theres todays lesson.
"Lets figure out why!" Bam.

 

[electrofelon]

We do both. The question still remains. When using the arrow, we subtract the rise. When we bend a back to back we utilize one mark and the star. I suppose we could make the second bend by subtracting the rise and using the arrow. So why don't we just use the star all the time?

Picture making a bend that is 10" to the back. Give it a try with the arrow in a place with 8' ceilings and let me know how it goes!

 

[rambojoe]

The best way to "lab"this is (2) 4sq mounted on steel studs either in the same bay or adjacent.
Doesnt matter, you can fab it on a sheet of plywood, point is to have a stud hole with one hole- inbteewn the (2) boxes.

 

[rambojoe]

Picture making a bend that is 10" to the back. Give it a try with the arrow in a place with 8' ceilings and let me know how it goes!

How about straight into a 2×4 lay-in, straight through the diffs. and lamps!
Dammit billy, i told you to not let me do that... my fav is a million dollar bend on the ground, get on lift and go up, just to demolish it on the roof... oops...

 

[rambojoe]

We do both. The question still remains. When using the arrow, we subtract the rise. When we bend a back to back we utilize one mark and the star. I suppose we could make the second bend by subtracting the rise and using the arrow. So why don't we just use the star all the time?

Did that help any?