PDF formulas and multipliers for bending conduit or electrical conduit
Dan has been an electrician for 17 years.He has a lot of experience in the electrical trade.
The most basic instructions for bending electrical conduit pipe are what most beginning electricians are taught.They can have a hard time bending larger conduit.More experienced electricians don't have a good idea of the wide range of possibilities.It's not hard to learn how to bend conduit to almost any angle.
It's easy to learn the math and formulas that make up a conduit-bending guide.If you want to do more complex bends, the only tools you need are an angle finder and a calculator.
Without a hand bender, an angle finder is necessary for any electrician bending large conduit.There are some examples at the end of the article.The calculator is free now that we have phones.The RealCalc scientific calculator app is free to download from the Play store.You can download RealCalc by searching the store.
The math of conduit-bending comes from two sources.The geometry of a triangle is one of the things that is built into a common hand bender device.
There is a lot of math in the hand bender device.To make offsets, saddles and 90 degree bends, only a few numbers and math operations need to be memorised.The figures are usually stamped onto the device.
The geometry of a right triangle can be used to calculate most conduit bends.
The pipe is bent.The bent piece of conduit is represented by a heavy black line and a green triangle.
The conduit is bent at the angle "d".The third angle is dependent on the first, being 90 degrees minus angle d.You can get the relationships between the lengths using the formulas below.
In real life, conduit is a three-dimensional object with curved, not sharp, corners.In everyday work, you can ignore these considerations because they only affect the measurements you use in a very minor way.
There are saddles that are used to route conduit.You can see how the triangle concept can be used for a three-point saddle by placing a second triangle back-to-back with the first one.
We will be using some math formulas.The relationships between the sides of a right triangle are dependent on the angle of the triangle.The formulas have equivalents in each case.The same formula is expressed in three different ways.
You can use your calculator to find the sine, cosine, and tangent of any angle.If you want to use the trigonometric functions in your calculator, you will have to read and understand the instructions for it.You will need to know how to get inverse functions on your calculator if you want to bend it.
radians are useless for the electrician if your calculator is set to describe angles in degrees.
The formulas will allow the electrician to bend any angle he or she wants.I have found myself trying to bend large conduit into odd angles and dimensions to match the demands of a building or get the appearance people want.It gets very expensive very quickly to bend conduit into odd angles.
It is possible to make the bending of large conduit easier by remembering these simple formulas.My own memory aid is this.
The side that touches the angle but is not the hypotenuse is the opposite side.
If you want to memorize the formulas, tape them to the back of your calculator.
This article is one of several written by an electrician.I will consider addressing your question in future articles if you don't find what you are looking for among my other articles.
There are two examples of angle finders from Amazon.One is cheaper, but the other is easier to use.Make sure that any one you choose has a magnet on at least one side to hold it to the pipe.
The article is correct to the best of the author's knowledge.Content is for entertainment purposes only and does not substitute for professional advice in business, financial, legal, or technical matters.
The only way to do it is if the bends are equal.The problem is that the bend needs to be matched to the largest conduit so instead of using the bender, it should be.
Anything that adds up to 180 degrees can be what the angles are.Those are INTERIOR angles.
Not in the sense of the formulas given here.The math used in the calculations is shown in an article.
I have a piece of conduit.I need to have 80" in the middle and 90 on each end.What is the length loss of a 90 bend?
The NEC indicates that the figure is 4.5" for 1/2 pipe.
The "length" of the bend is 4.5", but the pipe used to make it is 3.14* 4.5/2, or 7.The "loss" is either 7 or 2.5.The assumption is that the pipe is a pencil line and not a 3-dimensional object.I think the NEC figure is to the inside of the bend, meaning that the loss will be less than what is calculated, and the length is more than the minimum.
I am trying to bend a stick of EMT in the centerline of the conduit so I can get equal lengths on both ends.Is there a formula for that?
There is no real formula, but it can be calculated with a fair degree of precision.Divide the bend you want to make by 6.28 and then bend and divide by degrees.If you want to make a mark at the front edge of the shoe, divide the pipe by two and measure from the center.The bend should be close to the center of the pipe.If you use the NEC codebook to find the minimum bend, be aware that the figure given is to the center of the pipe, not the edge.
The same calculations as for an offset will give a close answer since the 90 is already bent.The lengths of C and A will be divided by the angle D in the diagrams.The figures will be close because of the difference in pipe thickness.
With the 90 already bent, that is all figured.I'm pretty sure you're asking where to put the 90 as it's a very different proposition as different pipes have different bends.The best way to figure out where the 90 should be bent is to add the shrinkage value to the number.Once bent, use the same multipliers as you would for bending an offset.It might be close enough for practical application in the field.
If the center line radius is 25 then how do I figure out the development for a 15 degree saddle bend?I don't know how to figure it out.
I am not positive what you mean by a center line radius of 25", but there is a link to an article on bending both 3 and 4 point saddles.
Is it possible to determine set and bend permissible length for bending conduit or electrical pipe?
Minimums can't be reduced because they are a function of the bender being used.You can set maximums as high as you want.I once made a 180 degree bend that was 100 yards across.It was a straight line.
I need a link where I can get your lessons in a hard copy, sir.I want to know more.
Dan Harmon is at dengarden.I'm a kid.I have been an electrician for 3 years and this website has been my go to for bending my apprenticeship.Everything has been converted to memory.I find myself coming back.This site is easy to understand.It made me more valuable and successful in my life.
I'm not sure if I understand the question.Make the same bends by measuring the conduit.You can use a protractor to measure the bends.
How do I figure out the bends and degrees for an existing conduit without removing the emt or rigid?
Great!Stuff.There will be a lot of piping when I start a new job tomorrow.I don't have a lot of experience with this, so feeding off of your hub has been very comforting.From here in Canada, I am grateful to you and your work.I think I will be more competent in my work.The information provided here is useful to any electrician.I will recommend this to any electrician who wants to learn or improve on their skills.
I liked the comments in your article.I am an EC in Illinois.One of the first things apprentices learn is bending conduit.My undergraduate degree is in applied mathematics and I often make the mistake of assuming my new hires are the same.I have sent links to your articles to all of my employees because I found your explanations of the calculations easy to follow.They will find them helpful.
The distance between marks is 4 1/4" if you want an offset of 2 1/8" at 22 degrees.When doing 90 degrees on a hand bender, there is no deduct.There will be Shrinkage, which can be found by the math formula of Shrink of.31, in your case.
I would like to know how we deturmine the deduct for a bend.I did not write it down when doing it, but I am not sure what to add to account for the loss in the bend.There are 3 conduits.It is my first non-90 bend, and I will be winging it in a second.I need a starter at starting height.
This is a great write up.I always wondered how those pipes were bent.It was a formula all the time.You learn something new every day.Thank you.
This is great!My husband tried to show me how he calculates all of this but it was beyond me.It made sense because of your easy to follow explanations, pictures and images.Thank you so much.
Good for you, Jane.Hope the information has helped you.It was nice to know I was able to help.
Thank you!I was taught this in class and thought I would never have to do it, but after having some difficulty bending large conduit today I am!
That is the way it goes, John.I have done a lot of big pipe and have asked if I could teach them how to avoid costly mistakes, but have never had to build odd offsets into a cable tray.A lot of people are scared off by the word math.
Interesting info here.I usually use the trig functions to design pipe work.
I was warned a few months ago by my partner that he definitely wasn't going to have anything to do with the cable tray offset we were about to build.Well then, sez...Tell me what to do if you want to design the thing.It seems like you have a better way to go than me.I want to learn something new.There was a long pause.It got a bit longer.
If he didn't ask me later if I would go over some of the fine points with him, he finally decided to weather the awful process of my math usage.
It was all about the basic trig, which many people were afraid of back in the day.The person is from Detroit.
It made sense to me as well.It must be of use to you if you are happy with the hub.That is always good to hear.
That makes sense, thanks for the explanation.It is an example from the ugly edition of 2011.The wrong page brings you to hand signals.I am glad I found it!!
Are you talking about an example in the movie?I can only guess, but I think it's because the pipe is three-dimensional.This means that 1.25 inches is close to half the OD of a 2 inch pipe; they are probably measuring the minimum radius at the center of the pipe rather than choosing either the inside or outside of it.This isn't usually important in smaller conduit, but it does come into play in the bigger stuff.
Adding that 1.25 will result in a measurement to the outside if the radius is considered at the center.If you want to fit another pipe onto a rack next to the one you already have, you need to have a radius of that figure plus the distance between pipes.
I am curious as to why you would add 1.25" to determine the minimum radius of a conduit.
A parallel offset is what you are referring to.You would make a mark on the first pipe of the off set.Depending on the distance between your pipes and the diameter of your second pipe, the mark will be moved.The formula is half the offset angle and the distance between pipe and diameter.If you had a left to right pipe and a right to left pipe, you would make the following marks, measuring from bottom up.Mark 1 at 24 and Mark 2 at 36 has an offset of 6 and a bending angle of 30.This gives us 2.125.Half of this 2.125" is 30 degrees and the other half is 15 degrees.We have 2.125" x tan(15), which gives us 587.To covert this to inches, we use 16 to get 9.122, so we now know that.5695 is close to 9/16".We subtract 9/16" from 24" to get 23 and 7/16".This is the first mark for the pipe.Our second mark will be close to 35 and 7/16.If you draw your pipes first, you can see how your marks will move on each pipe.The joy of being able to draw on the unfinished wall.
It depends on what you are doing.The section on examples has a 3 point saddle.There is a difference between "b" and "c" in the first diagram.
It depends on what angle the center bend is to be bent at.For complete instructions for saddles, visit thedengarden.com.
When bending a 3 bend saddle, my mark A is 30 inches and I am crossing an object of 3 inches.
A few additions need to be made.The 2.5" per inch of rise applies to a 22/45 saddle, not a 10/22 or a 30/60 degree saddle.At the center of the chosen degree is where the "B" bend is located.The bends must be reversed.If the order of bend is A,B,C, the bender should be reversed after the first bend.
Line "C" should be marked using the same measurement as line "B" above but on the opposite side of the center line.
Thanks Ron.This article was prompted by the fact that I have done a lot of large EMTs.When dealing with 4" conduit, there are many mistakes that get very expensive very quickly.That is not the time to experiment or make guesses.
I have been doing electrical work for 35 years.After starting out wiring houses, I went to schools, hospitals, grocery stores and now work as a lineman at a utility company.I find the information you have shared useful and necessary to do a professional job, and I really enjoy it.It is not easy to fix a wrong bend when working with large rigid conduit.
It's huge to know electric codes.Depending on your choice of fields, you may or may not need to know how to bend conduit.The homes have little to no conduit bending.Learning to read blueprints is important.
Depending on the state you live in, you may be required to attend school and work as an apprenticeship learning the trade.Check your state and local laws to find out what it takes to be an electrician.
I would like to be an electrician.I am going to learn about electrician tools, wiring, how to wire up motors, power distribution, electric codes, blueprints and electronic component circuits.Which is the most difficult thing to learn?I have heard that conduit bending is a bitch.
It is 1/2 of a 90 so we use 22.5 degrees.You can either take 1/2 of a 45 or half a 90.
It does work well if you divide 60 by the angel.If you need to be closer than that, you will probably have to change it.
The angle is 1/2 of a 90.Making bends easier.As a general rule, if you need to make an uncommon degree offset, your multiplier is how many times the degrees goes into 60.6017 is 3.5.It got me close to bending rigid ocal.Within an hour.
The amount that you loose in your entire length of pipe when bending a 90 is what jerome meant by "take up".It is useful to know if you want to cut and thread your pipe before bending it.
The chart above shows the multipliers of a 30 degree offset.Did you pick up an error in the article that I missed?
The mark on a hand bender is for a 22.5 degree, which makes the multiplier 2.6.
If you are using a 30 degree angle, your multiplier is wrong.The degree is around 2.4.
There are probably more memory aids than people.I would have a harder time remembering Sohcahtoa than the formulas.Thanks for the tip, a history buff might use it.
Thanks to cablemanagements.It's not common knowledge that a bending pipe is used in a practical way.It has been useful since I got curious one day and put some of my college math to work.
Very detailed information.It will take days to understand and experience.Thanks all the same.
I think you just overbent it a little.It is likely that it was in accounting for spring back, especially with the small degree bends.
It sounds like you are doing well.You will be a pro if you use that bender a little more.
I use the bender standing upright, it has a stand and a small plate that slides along as it is bent.I use the angle finder at our shop to find angles.
I think I bent the pipe when I was trying to compensate for the spring effect.
The thing that holds the pipe to the shoe should be made with more precision, like I said, because it ends up bending where you didn't think it would.I want to keep my calculator in my truck.If I can get it down to the science that I know it is, I would be happy.
When I was in high school, I decided against trig because I wanted to talk to all the honeys in business math.That's right.
There is a 13 degree bend if you have a 6.5" offset and marks of 28.75" apart.The trig works for any and all pipe size or bender.
This can be done with large benders.It is always a hassle to use a Greenlee bender for larger pipes.There are some thoughts here.
The bender requires someone to hold it from falling over.The end of the pipe is bent upward.It is important that the pipe is horizontal at 0 degrees.Sometimes a different shoe can be used to set under the end of the conduit to level it.I use a protractor to measure the bend being produced, then relax the pressure and re-check.
It isn't always easy to get the two marks at the same place on a big pipe.Sometimes the "hook" that the pipe fits through doesn't want to go all the way back to the shoe.All of these things need to be checked.
It is very easy to bend the pipe at ten degrees.A 3 degree deviation from what you want is 30%, while a 30 degree bend and go over 3 degrees is only 10%.Many protractors are difficult to read, and 1 or 2 degrees off is common.
You are on the right track, and your math is correct, as you discovered that the multiplier for 10 degrees is not 6 but 5.75 - it is just a usable figure that is easy to work with.Are you measuring with the rod that comes out to indicate bend, or are you using the bender on it's side?It's a little off, but 10 off would be horrible.A poorly placed protractor is an example.
I have been bending large pipe with greenlee benders for many years and they have made improvements over the old models.
I tried 10 degrees after bending the first at 22, but it seems the multiplier is too big.I tried 5.75 and came out with a 6.5" offset.
I did not space my bends at 37 like I said.My boss said there wasn't a formula, but I know there is.
I think my pipe will be getting a nice new one, at least it wasn't too small.
I have tried to duplicate the results I had at work.I needed an offset of 5 to 5 1/2 inches.It was over 9 inches when I tried 22 degrees as close as possible.I tried 5.75 with a spacing of 28.25 and was unsuccessful.The result was a 6.5" offset.Please verify if my calculations are off or if I am missing something, I never took trig but my calculator did and I can recreate your results on paper with it but the multipliers don't seem to be working.
Is that a thing?The deduct numbers are different for each size of conduit.It is stamped on every bender, just as you say.
For a 90, deduct 6 inches.It will look bad if you use a hand, but it will be stamped on the side.
To use the result on a tape measure requires the use of fractions, even though it is much easier that way.To memorize the decimal to fraction equivalents was my solution.In other words, 1/6, 2/8, and so on.If you divide 1 by 8 by.125, you can find these on a calculator.
When the result doesn't match one of the numbers, I choose the nearest one.I have never found it necessary to measure closer than 1/8" in the field.
I understand that in class that might not be close enough, and you could memorize each repetition, but it will not match exactly.Pick the nearest fractional equivalent to the calculated decimal figure in the final analysis.
Please let me know if I have confused you with something you can use.
Going to school for bending conduit and learning about shrink and gain.I just passed ac theory and have trouble with fractions and decimals.They keep saying it is very close to my answers.I would not use them in the feild.You can give me some advice, I only bent conduit by eye and a tape measure.
I am not familiar with that term, it is not used in my area.Do you refer to theduct when making a 90?The bender used would affect that.The multipliers used in offsets are not dependent on the size of the conduit.
What is the take up for rigid conduit, 1 1/2, 2, and 3?
One of the more useful bends is the rolling offset.The biggest problem is how to measure the needed offset.
For someone who has no training in math at all, even simple addition or subtraction of fractional figures can be difficult.The math in this hub is not where to start if you start simple and go from there.Learn how to use the deduct of a 90 and worry about the trigonometry of large conduit offsets later.
If you don't understand math, conduit bending is one of the hardest things to teach.
I start with the basic bends.I will show them more bending techniques after they master them.
You are welcome.I enjoy sharing my knowledge with others.I am happy that you found it useful.
You are welcome.It is a pleasure to share what I have learned, and I am always happy when someone finds it useful.
It is, although few electricians use it.Most of the time the math is built into the tools we use, but as I am sure you know, it is behind many things we take for granted.This could help students realize how important it is to learn and understand math in everyday life.
I did not know that trig would be relevant to bending conduit.I will use this new knowledge when teaching reluctant math students.