Electrical Metallic Tubing (EMT or conduit), especially in nominal 1/2 inch size is very handy for structural projects, as well as relatively inexpensive. I could weld pieces together where I need to turn a corner. But, the zinc coating welds poorly and makes dangerous fumes. It needs to be removed, but that is not always easy. I decided I want a conduit bender. But, I do not want to pay $30 plus for one at Lowe's or Home Depot. I decided to use scrap steel I already have to make my own.
- Steel tube about 3/4 inch internal diameter
- #10 gauge sheet steel
- 1/4 x 3/4 inch steel bar
- Steel for a handle
- Angle head grinder and cutting wheel
- Wire feed welder
- 3 pound hammer
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Step 1: Select Tubing
1/2 inch EMT has an external diameter just under 3/4 inch. I selected some heavy scrap steel tubing that was just large enough to slide over the EMT.
Step 2: Slice the Tubing Lengthwise
I clamped the tubing in a vise with a piece of angle iron I used to guide the cutting wheel on my angle head grinder. I sliced the opposite side of about eight inches of tubing to cut the tubing into two halves. Only one of the halves wills be needed. (The slicing is a little tricky, especially as the cutting wheel is about to break through on the second cut.)
Step 3: Kerfs for Bending
I cut multiple kerfs across the tubing half. Kerfs were not quite 1/2 inch distant from one another. The kerfs all but cut the half of the tubing completely through.
Step 4: Bend and Tack Weld
I bent the kerfed tubing half to a radius close to five inches. I was cautious about tack welding because welds cause things to shrink and too much welding would have caused the desired radius to change. This curved half tube needs to extend over one-fourth of a full circle, or 90 degrees.
Step 5: Mark and Cut a Convex Curve
I added a steel framework to assure the radius of the tubing half will not change in use. I used masking tape to record my mark and then cut it carefully with a cutting wheel on an angle head grinder.
Step 6: Tack Weld
I held the two pieces together by hand and tack welded them together.
Step 7: Weld
I welded relatively short beads and changed the location where I was welding often to keep from distorting the curved half tube. In the photo I was closing the kerfs I made to bend the half tube.
Step 8: Handle, Etc.
I took more photos, but auto-focus gave me photos with a sharp background and a blurred main subject.
I had a heavy piece of "U" channel about four feet long. I welded it to the sheet steel to make a handle for my bender. (See the text boxes in the first photo.)
I added a hook to pull the end of the conduit into a curve during bending. The hook is made from 1/4 x 3/4 inch steel bar. I bent it with a 3 pound hammer and a vise. See the text boxes. The hook was too flat and the end of the conduit was egg-shaped after bending. (Later I used a carbon arc torch on a 230 volt stick welder to heat and shape the bend in the steel bar so it followed the contour of a solid piece of steel round bar almost the same size as the EMT. See the second photo.)
Step 9: Foot Lever
I was my father's helper when he did electrical wiring. He had conduit benders. I made a few bends, mostly in 1/2 inch EMT, but never became expert at it. New conduit benders have added a foot lever to make bending easier. I used some 1/4 x 3/4 inch steel bar to add a foot lever to my bender, too.
My bender works quite well, especially for structural pieces to make a framework for a welding project. I need to study this document from Klein Tools to learn how better to place my bends exactly where I want them. I may also need to measure and study some bends made with my bender to make some marks on the bender for precise placement and bending.
I enjoyed the challenge of making my own conduit bender. It was good to use up some scrap steel taking space in our garage, and it was good to get additional practice welding. I will get good, if only occasional use, from this conduit bender. If necessary, I could use it to bend conduit for an electrical wiring job, although that was not my purpose in making it.
The next step is an addendum telling what I know now about placing the bender for precise bends.
Step 10: Placing the Bend
See the first photo. I wanted to know how much conduit is used to make a bend. Before bending the conduit, I made marks 6, 7, 8, and 9 inches from the end of the conduit. The end of the conduit was even with the outside of the hook. See the second photo. The rear edge of the bender aligned exactly with the 9 inch mark when a 90 degree bend was completed. The second photo is an attempt to determine the stub out of the bender. A commercial bender has a standard stub out of 5 inches. My bender has a stub out of about 5 1/4 inches. I may learn a more efficient way to place the bender, but assume the vertical bend at the left side of the second photo needs to fit something 84 inches from the end of the horizontal portion of the EMT not visible in the second photo, subtract 5 1/4 inches from 84 inches. The answer is 78 3/4 inches. Measure 78 3/4 inches from the right horizontal end of the EMT. Add 9 inches to that and mark the EMT. Place the bender on the EMT and move the outer or top edge of the hook to align with the mark. Make the 90 degree bend. The distance from the EMT end off of the right side of the second photo to the left edge of the vertical bend should be 84 inches.
As an illustration, see the third graphic. The thin black rectangle is a piece of EMT tubing. When the bend is finished, it needs to replicate the pink line with the bend in it. It needs to fit between the two vertical black strokes marked as 84 inches. The left end of the red/orange line aligns with 84 inches. The red/orange line is 5 1/4 inches long. Measure to the right from the 84 inch mark a distance of 5 1/4 inches. The green line represents 9 inches. Measure to the left a distance of 9 inches as represented by the blue line. Place the outside edge of the hook on the mark where the left end of the blue line falls. Make the 90 degree bend. The completed bend should yield a piece of EMT that fits between the black strokes at 84 inches just like the pink line.