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Old 05-31-2010, 11:35 PM   #1
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Default 30 degree offsets

How would one figure out the minimum size offset you can make using the 30 degree bends? Obviously there has to be a minimum size because of the size of the bend. Is there a chart?

If we use 3/4" EMT as an example, the takeup for a 90 bend is 6 inches. So 1/3 of that would be a 30 degree bend, or 2 inch takeup. Is that the same as the offset amount?

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Old 05-31-2010, 11:42 PM   #2
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I thought you were conduit Phil???????

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Old 05-31-2010, 11:45 PM   #3
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On a short offset like that I like to use 10s. It makes it easier to pull.
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Old 06-01-2010, 12:14 AM   #4
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Phil,

If you need a 10" offset, using 30deg. bends, you need 20" between bends.

Is that your question ?

Ok, the smallest offset would be the measurement from the arrow on the

bender to the front of the bender.
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Last edited by Benaround; 06-01-2010 at 12:21 AM. Reason: add info.
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Old 06-01-2010, 12:16 AM   #5
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It's all just math. However, you're thinking it's a linear relationship, and it's not.

If the take-up of " EMT is 6", then you could make a 360 circle with a 6" radius.

So what would the circumference be? Pi*r*2. 3.14*6*2. 3.14*12. Or 37.68".

So a 360 circle is 37.68" in circumference. From that, you can calculate how much of that is used in each 30 of arc. Double that for an offset.
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Old 06-01-2010, 12:41 AM   #6
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480,

Been a while since math class... 360/30=12. So there are 12 30 degree arcs in a circle.

37.68/12=3.14

3.14 is the minimum offset? Not sure why you'd double it. You are kicking it one direction and then back the opposite.

Thats close to 4 and the guide on porcupinepress.com says "30 bends are too great with most hand benders for offsets less than 4" center to center."
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Old 06-01-2010, 06:40 AM   #7
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Originally Posted by Conduit Phil View Post

3.14 is the minimum offset? Not sure why you'd double it. You are kicking it one direction and then back the opposite.
Because using 30 deg bends you double the offset for your bend points. Using 45 deg bends you use 1.8 times the desired offset.




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Thats close to 4 and the guide on porcupinepress.com says "30 bends are too great with most hand benders for offsets less than 4" center to center."
Huh??
You take the conduit out of the bender and turn it around? That is not how most people do it. Not unless you have to that is.


Heck, using 3/4" I cannot see how it would be physically possible to get bends closer than roughly 4".
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Old 06-01-2010, 08:32 AM   #8
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Because using 30 deg bends you double the offset for your bend points. Using 45 deg bends you use 1.8 times the desired offset.
What kind of bender do you have? I've always used 1.41.
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Old 06-01-2010, 09:00 AM   #9
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480,

Been a while since math class... 360/30=12. So there are 12 30 degree arcs in a circle.

37.68/12=3.14

3.14 is the minimum offset? Not sure why you'd double it. You are kicking it one direction and then back the opposite.

Thats close to 4 and the guide on porcupinepress.com says "30 bends are too great with most hand benders for offsets less than 4" center to center."

You double it because, well, you need two bends to make an offset.
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Old 06-01-2010, 09:07 AM   #10
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You double it because, well, you need two bends to make an offset.
Stop confusing me with such facts.
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Old 06-01-2010, 09:15 AM   #11
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Stop confusing me with such facts.

OK, Bob. Just for you, I'll let you make 2 bends.
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Old 06-01-2010, 09:39 AM   #12
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OK, Bob. Just for you, I'll let you make 2 bends.
Bending takes to much time anyway just 'bow and go'.
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Old 06-01-2010, 10:53 AM   #13
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Bending takes to much time anyway just 'bow and go'.

Nah just warm up the pvc blanket and shape as needed
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Old 06-01-2010, 07:27 PM   #14
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Bending takes to much time anyway just 'bow and go'.
You must really get around. I've seen your work all over the place.
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Old 06-01-2010, 07:28 PM   #15
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How would one figure out the minimum size offset you can make using the 30 degree bends? Obviously there has to be a minimum size because of the size of the bend. Is there a chart?

If we use 3/4" EMT as an example, the takeup for a 90 bend is 6 inches. So 1/3 of that would be a 30 degree bend, or 2 inch takeup. Is that the same as the offset amount?
Hey Phil,

There is no chart that I know of. The min. offset would vary with each size conduit and bender type.

To determine the minimum offset on a specific bender/ conduit size, Multiply the amount of offset desired by the cosecant of the angle desired: (30 deg = 2; 15 deg = 3.86; 10 deg = 5.76). This measurement must be enough to line up the second bend mark on the correct center mark for the angle desired- (this will NOT be the star mark for a 90 deg stub), and have enough conduit to have the first bend mark about one pipe diameters past the end of the shoe. This is way easier to demonstrate than to explain.

I always mark my hand benders with the center marks for 5, 10, 15 and 30 degrees. This makes bending faster, more neat, and easier to match multiple runs.

On my usual 3/4 ENT bender, a 2 inch offset on 30 degrees is the minimum offset. I would normally bend any 3/4 EMT offset, less than 3 inches, on 15 degree or less bends. It looks neater and is easier to pull wire.

Does anybody remember the days of concentric bending?
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Old 06-01-2010, 07:49 PM   #16
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Hey Phil,

Does anybody remember the days of concentric bending?

What's a do hickey
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Old 06-01-2010, 08:01 PM   #17
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On that note, does everyone prefer 30 degree offsets?

After this job, I'm beginning to rethink my use of them.

Granted, they ran 1/2'' pipe where solid 12's and 10's were being pulled through, but to prevent pulling fiascos like that in the future, I'm considering stepping it down to at least 22 1/2 as a baseline.
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Old 06-01-2010, 08:21 PM   #18
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On that note, does everyone prefer 30 degree offsets?

After this job, I'm beginning to rethink my use of them.

Granted, they ran 1/2'' pipe where solid 12's and 10's were being pulled through, but to prevent pulling fiascos like that in the future, I'm considering stepping it down to at least 22 1/2 as a baseline.
I prefer 15 degree offsets myself, as long as they are not huge. They do make wire pulling a lot easier, especially if I am working alone.
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Old 06-01-2010, 09:56 PM   #19
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What kind of bender do you have? I've always used 1.41.
Duh.
I knew that but wrote it wrong anyway.
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Old 06-01-2010, 10:06 PM   #20
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On that note, does everyone prefer 30 degree offsets?

After this job, I'm beginning to rethink my use of them.

Granted, they ran 1/2'' pipe where solid 12's and 10's were being pulled through, but to prevent pulling fiascos like that in the future, I'm considering stepping it down to at least 22 1/2 as a baseline.
I like the 30 degree bends. As long as you don't give into the temptation to overfill the conduit it should be no problem. Teaching others the way around a Chicago bender is easier and the learner will remember that, and how to figure the gain and the loss of that bender, and how much loss you have to figure into the calculations to be able to cut and thread a straight piece of pipe before bending a 90 degree and an offset on the same piece. Just my opinion.

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