EMT Electrical Conduit Pipe Bending - How to Bend a 90
EMT Pipe Bending
Bending EMT is one of the more common tasks for both commercial and industrial electricians, and it is not difficult to learn. This hub is designed for the beginning electrician, that they may pick up some pointers in using a hand bender to make a 90 degree bend in electrical conduit. More experienced electricians may be interested on another hub on how to make a concentric bend.
There are three basic 90 degree bends; the plain 90, a kick 90 and a double 45 90. Each has its uses and should be learned by the electrician; each will be treated separately in this hub. Read and understand the conduit bending instructions here and try to get some "bones" (scrap conduit) from a job site to practice on. A little practice and you will quickly become proficient at bending a 90.
How To Make A 90 Degree Bend
A simple 90 degree bend in electrical conduit; it sounds easy, and it is, but there are a few considerations to make. First on the list is to understand the term deduct; this is a measure of the amount the conduit will "shrink" in length when a hand bender is used properly. It is different for each size of bender (½", ¾" and 1" benders) and some brands of benders are different as well. The most common deducts are 5" for ½" conduit, 6" for ¾" conduit and 8" for a 1" bender. It is a function of the curvature radius of the bender and cannot be changed. The deduct for your bender should be stamped on the bender.
To use the deduct figure, measure the distance to the far edge of the 90 and subtract the deduct figure. If ½" pipe is being bent and the distance is 56" place a mark on the conduit at 51"; this is where the bender will be placed.
Work the bender onto the conduit with the conduit mark at the arrow of the bender. There are some slight variations in the location of the arrow on different brands, but it is basically at the beginning of the curve of the bender. The bender must be oriented with the toe of the bender pointed toward the end of the conduit measured from. To phrase it differently, point the toe of the bender toward the end of the conduit where the tape measure was hooked to measure from.
With the conduit on the floor apply firm foot pressure to the foot pedal of the bender and slowly move the handle of the bender toward the floor. Much of the bending pressure will come from the foot pedal - if there is not enough pressure on the pedal the conduit will kink instead of making a smooth bend. As the conduit rises into the air, grasp it with your free hand and apply a small amount of pressure there to steady it. It is good practice to stop bending just before it appears to be a true 90 degree bend and check it with a level. It is easy to add a few more degrees; not so easy to take some out. Be aware that the weight of the bender will cause a small amount of bend that will disappear when the bender is removed and the conduit springs back very slightly.
The above method works well for shorter lengths, but when a long measurement is needed it will not work. For instance, if the measurement is 110" in a 120" length of conduit the bender will have only 10" to work with and it is difficult to impossible to make such a bend, particularly in ¾ and 1" conduit. The answer is to turn the bender around and point the foot pedal toward the end measured from. Do not use the deduct! Mark the conduit at the full length desired and again work the bender onto the conduit. This time line up the star on the side of the bender, about half the way around the bender, with the mark. Bend as before. This method of measurement and bender placement is commonly termed a "backbend"
Bending a 90
Bending a 90 degree bend
Bending a Kick 90
A kick 90 is, very simply, a 90 with an additional small bend in it, either raising or lowering the end of the 90. It might be used on a conduit going up inside a wall but that needs moved over and outside the wall when it continues, via the 90, on the ceiling. The same thing can be accomplished with a 90 and an offset, but this requires additional bending and makes wire harder to pull. Always limit the number of degrees of bend in a conduit run to the minimum possible.
First bend the 90 and choose a spot to add the small "kick" bend. The closer to the 90 it is the more degrees it will require, but at the same time if it is too far away from the 90 it will look decidedly odd. Mark the conduit and place the bender mark for a normal 90 degree bend at the mark. Make sure the 90 is turned the proper direction or the kick will be bent the wrong way. Visualize the resulting conduit before bending, perhaps while holding it in the proper orientation. Normally kicks are bent to a particular measurement in inches rather than degrees. With the bender in place on the conduit and on the floor ready to bend, apply pressure the the bender, but just enough to tighten up on the conduit so it doesn't slide or turn. Verify with a level that the 90 end is level, and measure from the floor to the top of the conduit 90. Measure how high the 90 is from the floor (see pictures).
Begin to bend, watching the tape measure carefully until the conduit is at the correct height. This will be the desired kick amount plus the first measurement taken. For instance, if the first measurement is 1 ½" (a reasonable amount with the bender just tightened slightly) and the desired kick is 4" the final measurement to the top of the conduit should be 5½", Also be aware that the side of the 90 with the kick will shrink in length; the shrinkage is extremely variable so it is best to simply make the 90 too long if that is where the kick will be and cut to the right length.
A kick 90
A Double 45 Degree 90
The final method of making a 90 is to make two 45 degrees instead. There will sometimes an obstruction in the corner of two walls or a wall and a ceiling where a typical 90 needs to pass. The answer here is to bend two 45 degree bends with a short section of straight conduit between them. The total bend is then 90 degrees, but the path the conduit follows misses the actual corner of the wall.
To make the bend, measure the distance to the corner (not the obstruction). Decide how far back to make the first bend so that the conduit will miss the obstruction if bent at 45 degrees. Just a little practice here and you will become quite proficient at making this call. Deduct that measurement from the one to the wall and then subtract 1 more inch. The extra inch is necessary as conduit is not a thin pencil line, but a thick 3 dimensional object making rounded bends instead of sharp corners.
Example: Distance to wall is 50", it has a 3" round pipe right in the corner and you feel that making a 45 degree bend 6" from the wall will clear the pipe. Mark the conduit at 43" (50" - 6" - 1"). Now multiply the 6" figure by 1.4 (6" X 1.4 = 8.4" or about 8 3/8") and make a second mark 8.4 inches past the first mark. Using the notch that indicates the center of a 45 degree bend to line up with the first mark, make a 45° bend; slide the conduit forward in the bender and, making sure the conduit hasn't turned in the bender, repeat the process. You now have a 90° bend that will miss the corner obstruction.
Many electricians prefer to make these smaller bends "in the air" as it is much easier to get the proper bend. If you are not sure about this, a good read might be EMT Electrical Conduit Pipe Bending Instructions, which includes a section on bending offsets in the air.
A final note - this article is but one of several written by an electrician, for electricians. A comprehensive guide to bending conduit has been written that gives a brief description of each page, along with a link to individual pages as well as a handful of other links to pages electricians might find useful. Feel free to check out this title page for anything else that looks interesting. If you don't find what you are looking for, leave a comment and it will be considered for future pages; the whole series is, and will continue to be, a work in progress.
Bending a double 45
© 2010 Dan Harmon