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Thread: Conduit Bending 101

  1. #1
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    Conduit Bending 101

    Since many here want to install conduit in their workshops, I thought I'd get a conduit bending workshop going here. The only damage you can do is too the pipe, and maybe your ego. Of course, you need to have designed the system correctly. We can do that in another thread, if there's an interest in it.

    The benders:

    From left to right - 1" EMT (or 3/4" GRC), 3/4" EMT (1/2" GRC), 1/2" EMT and 1/2" EMT short radius bender. The two on the left are made by Benfield, the best but they are out of business now. The blue handled one is made by Ideal and the brand most seen on jobsites around here now. The short radius bender is made by Lew Fittings in Chicago but I think they are OOB too. Many municipalities outlawed short radius bends because they make wire pulling so much harder and that could put a strain on the insulation. But there are times when the short radius bend is needed, just make sure it's the only bend in a run and the pipe run is short, if possible. Two short radius bends in the same run will have you yelling at yourself for not heeding my warning.

    I've used benders by Gardner-Bender, Greenlee, Klein and a bunch of other brands I'd prefer to forget. If you can find an Ideal bender, buy it. If you find a Benfield at a flea market or something, grab it, immediately! They are the best. Good marks and very accurate. But whatever you do, don't buy one of those 1/2" & 3/4" combos. They will make you hate bending pipe. And forget the built in levels, they are a gimmick. Buy a good level (see below).

    A good bender has an arrow and a star marker on it, and graduated degree markings. There is also an indentation in the channel but we'll get to that later.

    We're going to start with a simple 10" 90 degree bend on 1/2" EMT. On all benders you have what is called a take-up. It's a number subtracted from whatever length 90 you want to make, when using the arrow on the bender. 1/2" benders have a 5" take-up, 3/4" - 6" TU, 1" - 8" TU. They are usually marked on the bender shoe.

    For a 10" 90, I made a pencil mark at 5" - 10-5=5. I use pencil because it's harder to see once the pipe is installed. Felt marks all over your work is very unprofessional looking. IMHO


    Take that pencil mark you made at 5" and place it at the center of the arrow mark on the bender. The take-up deduction is only used when using the arrow mark on the bender. The star we'll talk about later.


    The first thing you have to do is apply a good amount of foot pressure on the heel of the bender. If you don't do this, the pipe might kink and almost certainly throw your bend off. You can get an idea how much pressure I'm applying by the indentation in my gym shoe sole and the fact the heel on my other shoe is coming off the ground (gym shoes aren't recommended for pipe bending because the sole is too soft but they work OK for 1/2"). While keeping foot pressure on the heel, begin to pull the handle back. This is done all at once but only for 15-30 degrees at a time. This is the most critical time for keeping good foot pressure on the bender heel. Think of your foot pressure as making the bend and the handle a guiding the bender.


    Sorry for the blurry picture The bender handle is now perpendicular with the ground. (Keep this in mind, it will help with offsets when we get to that later on.) While you're making the bend, do the bending incrementally. Press you foot down hard on the heel while pulling the handle back. Do this in short bursts, making sure you don't loose foot pressure on the heel. DON"T TRY TO MAKE THE 90 IN ONE MOTION! That's how pipe kinks happen. As you get better, you'll get the hang of how much to bend per shot.


    The 90 is now 10" long, when measured from THE BACK of the bend. Keep this in mind when taking your measurements. If you have a box on the wall and you want to turn the corner with a 90, measure from the side of the box to the wall, subtract for the hanger you'll be using and then subtract the take-up and mark that on your pipe. Then line the mark up with the arrow.


    Look, ma, no kinks! If you want a perfect 90, place a level on the floor and see where it reads, then place the level on the 90.

    FOOT PRESSURE! FOOT PRESSURE! FOOT PRESSURE! I can't emphasize this more! It's the one part of bending most beginners fail to do. Overdo it initially until you get the hang on how much is needed. The handle is only there to aid the bending your foot is doing. And make all your bends in segments, like 10-30 degrees at a time. The bigger the pipe, the more foot pressure and the more bending segments are needed. I've bent 1-1/4" with a hand bender and it probably takes me 10-15 segments to complete a 90. I practically stomp on the heel while pulling the handle back. It requires all my weight. I am completely off the floor. Even big guys I've worked with have to put most of their weight on the heel with 1-1/4" EMT.

    It might not be a bad idea to use a level until you get good at it. And if you want a really professional looking job and don't have a level built into your eyes, a level is a must. This is a nice little level from Greenlee. It does it all.

    That thumbscrew is used for making offsets when you don't want a dog in the offset. We'll get to offsets in another post. And yes, I am holding that out into the air and failing to make it read level. But anytime you want to make sure you've bent a perfect 90 or 45 or 30, you need to first make sure the pipe laying horizontal is level, then check the bend.

    I think I covered a 90 degree bend completely. Any questions, just ask.

  2. #2
    Thanks for the tutorial, Julie. I doubt if I'll ever bend conduit but it's interesting to see how it's done.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  3. #3
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    Reaming conduit:

    When you cut conduit WITH A HACKSAW, NOT A PIPE CUTTER, it will leave burrs on the pipe. I use a 32T blade for pretty much all the pipe I cut, up to 1". It makes the smoothest cut but still leaves a burr. So you have to ream the pipe smooth. Pay attention when cutting to make sure the cut is square.

    You can buy a pipe reamer if you want. I think Ideal and Greenlee make them. But that's just one more tool you have to buy and carry around. I use Channel Locks for both the inside and outside when reaming and most other electricians do the same, at least us old timers.


    As you can see, these Channel Locks don't have insulation on the handles. Years ago, this was standard. That CL in the pictures is probably 30+ years old. Now it seems they all have insulation on them. Some electricians strip off the ends so they can fit inside the pipe for reaming. With Channel Locks, all you have to do is stick the ends in the pipe and twist it back and forth until you feel it's smooth. Your hand will tell you.

    You also have to ream the outside so it will fit properly in the fitting (coupling or connector). The jaws fit around the pipe and you twist them back and forth until smooth. You'll have to adjust the jaws to get a comfortable fit. Don't just do the inside! Again, very unprofessional.

    This is what the end should look like when you're done.


    I'll have to corral our son to pose for pics when covering offsets. It's impossible for me to pose and take pictures. I'm not that fast. But unless I get a request to cover something else, I'll do offsets and saddles next.

  4. #4
    Great stuff! Thanks Julie!

  5. #5
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    Julie,

    Here was my first (and only) attempt at bending conduit when I wired my garage shop. I was satisfied with the results even if not perfect. The piece that comes back down the support beam was the trickiest. I used my feet as much as possible, but as a 115 pound weakling, it was all pretty hard to do.

    James
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  6. #6
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    Thank you. Box offsets next? Please...

  7. #7
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    This is interesting. I am glad that conduit is cheap as I have made enough mistakes with it.

  8. #8
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    Quote Originally Posted by James Baker SD View Post
    Here was my first (and only) attempt at bending conduit when I wired my garage shop. I was satisfied with the results even if not perfect. The piece that comes back down the support beam was the trickiest. I used my feet as much as possible, but as a 115 pound weakling, it was all pretty hard to do.
    The bend at the end of the 90 in your second picture is called a kick. What is tricky about that is if you already bent the 90 along the side that you have to make the kick in because the kick shrinks the length it's in. if that makes sense. But a kick is better than an offset because it doesn't add additional degrees of bends in the run. The more bends, the harder the wire pull. And you have your code to consider too.

    The one you said was trickiest (3rd pic) is an offset but I can see it was (A) a pretty big offset, (B) in a short distance, (C) on 3/4" pipe, (D) with a 90 at the other end. Yeah, I understand why that was a challenge. But you did it, and on one piece of pipe (awesome!), and it looks really good! If that discouraged you from taking on any more pipe bending, don't let it. That was not an easy bend.

    Quote Originally Posted by Paul Mattaliano View Post
    Box offsets next? Please...
    Box offsets can be done with the pipe on the floor but I do them with the bender shoe up, where I can see the roll of the offset. You are trying to roll it exactly 180 degrees. It's two very short bends, 180 degrees from each other. And I mean very short. Box offsets usually go wrong by overbending the first bend. But pipe can be unbent. Take advantage of that with short bends that go wrong.

    When you put the shoe in the air, you have to concentrate as much pressure on the part of the pipe closest to the bender shoe as possible. For a box offset, that's only critical in respect to making a sharp bend. As you can imagine, if you put pressure at the other end of the pipe, you'll bend the whole thing. So you place as much pressure as you can close to the bender shoe. You can do it on the ground but it's a pretty small bend. Just bend it the way I showed above a few times and you'll know what I mean. Start by overdoing the pressure and you'll see the result. Then back off until you reach an equilibrium.


    I've probably owned this over 20 years. The only time I've used it is when I have lots of box offsets to make. And I mean lots. You'll rarely see this in an electrical contractor's gang box. They are more a pain than a time saver.

    You have to secure it to something (like the board it's on) or you'll never get an accurate offset. Otherwise, the whole thing rocks as you push the handle down and it's a pain. It's another one of those, "How many tools do you really need to do the job?" Before you plunk down the cash for the offset bender, give the other method a try. Unless you're really impatient or like buying cool looking tools, you won't find any need to own one.

  9. #9
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    Julie, the take up dimension is the distance the mark will be off the initial plane after a 90 degree bend, yes?

  10. #10
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    Quote Originally Posted by Steve Rozmiarek View Post
    Julie, the take up dimension is the distance the mark will be off the initial plane after a 90 degree bend, yes?
    The take-up is a dimension fixed for different sized benders when using the ARROW mark on the bender to make the bend.
    - The take-up on a 1/2" bender is 5".
    - The take-up on a 3/4" bender is 6".
    - The take-up on a 1" bender is 8".

    This is the amount you will subtract from the actual dimension needed to make a certain length 90. That dimension is measured from whatever point you will be starting - panel, box, end of last piece of installed pipe - to wherever the BACK of the 90 needs to be.

    In this case, we subtract the dimension the mini (conduit hanger) spaces the pipe off the wall. Then subtract an additional 5" and use that measurement to make our mark on the pipe (MARK HERE) from the end of the pipe (the end going into the connector on the box). And in all cases lining that mark on the ARROW mark on the bender. You never use the take-up with the STAR mark on the bender. Where you see MARK HERE, is where you made your pencil mark before starting the bend.

    If you have any questions, just ask.

  11. #11
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    Thanks! You're inspiring me to try the bender again. (been doing straight runs from box to box to avoid it!)

  12. #12
    Julie, I have a quick question about what size conduit to use. I will be putting three wires through the conduit if that is ok. Two circuits of 240 and one 120 circuit. Would that all fit in a 3/4 conduit or would that be too tight? I am going to go out looking at the local pawn shops for a cheap bender today and want to get the right size. Thanks again!

  13. #13
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    Great info Julie, thanks. I need to put in s compressor run and will probably add some 120V outlets too. This is helpful.

    Doug

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    Quote Originally Posted by Steve Wilde View Post
    Julie, I have a quick question about what size conduit to use. I will be putting three wires through the conduit if that is ok. Two circuits of 240 and one 120 circuit. Would that all fit in a 3/4 conduit or would that be too tight? I am going to go out looking at the local pawn shops for a cheap bender today and want to get the right size. Thanks again!
    Anyone will need more information before answering your question. What size and type of wire? #12 THHN? Are your 240 circuits needing a neutral for 120 or are they straight 240 circuits? Are you going to be running a separate ground wire? Even with that info, I will let Julie answer. Although the answer will ultimately come from the NEC conduit wire fill tables.
    NOW you tell me...

  15. #15
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    There was another thread about the number of CCCs (Current Carrying Conductors) allowed and from her experience, the fill with 3/4" conduit was 9 and this counts hots only...no white and no ground. So Steve, you are mostly likely fine to pull that number through 1/2".
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