back to back 90

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liquidtite

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when ever I bend a back to back 90 weather it makes a u shape or going in opposite directions ive seem to be a inch or so off.The way it says to bend back to back 90*s in uglys book is to bend your first stub up by using the arrow and then deducting,after you have you first 90 bent then use the star on the bender and bend your next 90*.I asked a mechanic on the job and he said that the star is hard to line up and it never gives you a true 90 were your mark is to go of off.He said that on his second bend he adds I think he said 3 inches for 3/4& and bends in the opposite direction than if you were using the arrow he was only explaning this to me so i wasnt able to picture this and he didnt have alot of time to go over in detail.Can you bend your second 90 the same way you do as your first stub by deducting and using the arrow if theirs enough room, and how do you bend a 90 the way he said on your second bend by adding if i heard him right.I would just practice at shop or on job but my boss is a ball buster and dont feel like having more discussion than nessary, thanks for your time much appreciated
 
Dude, there is a big button just to the right of your right pinkie labelled "Enter". Hit it every now and then after you use a period. It will make your posts easier to read.

I never use the star. First bend burn 6" of the end of the pipe, mark and line up the arrow. Add three inches to your second measurement, rotate your bender one hundred eighty degrees and line up the arrow again and bend.

For practice I would use some 1/2 inch and the same ratio.

There is a trick when things don't go like you want. It involves unbending a bit and then sliding the bender up and bending again. I don't know how to explain it right now.
 
My bad on the post being so crazy . SO on the second bend you add three inches and rotate bender 180' .Now if your back to back 90 is a u shape the nose would be facing the first 90?
 
ActionDave said:
Dude, there is a big button just to the right of your right pinkie labelled "Enter". Hit it every now and then after you use a period. It will make your posts easier to read.

I never use the star. First bend burn 6" of the end of the pipe, mark and line up the arrow. Add three inches to your second measurement, rotate your bender one hundred eighty degrees and line up the arrow again and bend.

For practice I would use some 1/2 inch and the same ratio.

There is a trick when things don't go like you want. It involves unbending a bit and then sliding the bender up and bending again. I don't know how to explain it right now.
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Don't you add 3 inches for 3/4" because of the 6" take up to the mark of a 3/4 bender for regular stubs? For 1/2 inch you likely would only add 2-1/2", and for 1 inch you would add 4".
 
liquidtite said:
Yes your correct I've tried 3/4 and its 3". 1/2 is 2.5 etc is half of what ever take up is
Click to expand...
Been a while since I've bent any EMT or used a hand bender... but I do remember the methods.

To make a bend backwards, what you add is (deduct - gain). You can determine gain by measuring a straight piece before bending, then measure both legs after bending and sum. Subtract straight length from sum, and that is your gain.

Mathmatically, gain for a 90? bed is .4292 times the centerline radius. The deduct essentially reflects the centerline radius plus one-half the O.D. But that's on paper. Deduct isn't always to the point where the bend starts. That's obvious when using a power bender such as a triple nickel.

Anyway, not feeling like getting my hand bender out and dusting it off, and putting a 90? bend on the only straight piece of conduit I have set back for a project which I never get 'round to... I did the math and it says the following...

EMT, Deduct, Gain, Adder
1/2, 5, 2, 3
3/4, 6, 2-3/8, 3-5/8
1, 8, 3-3/16, 4-13/16

In practice, use the measure-actual-piece method to determine gain and adder :happyyes:
 
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