Pulleys are no big deal to make

Ron Thompson
December 19, 2001

I turned a couple of pulleys the other day for a rotary phase converter project I am working on.

I started with a 2" diameter bar of cold rolled steel mounted in the lathe and cut a groove to depth with a parting tool. Being careful not to bind the tool and break it, I cut almost 2 grooves wide a little on each side until I got deep enough.

Then I set the compound to 17 1/2 degrees to cut one side of the tapered groove and then 17 1/2 degrees the other way to cut the other side. The groove needs to be deeper than the belt so the belt can ride lower as it wears.

Then, with the part still in the lathe, I drilled and reamed to size for the shaft. Everyone knows drill bits drill a little oversize, right? If you want to know how much, drill a piece of scrap first.

Then came the keyway broaching. I had never done this before, but it was a breeze. I oiled the bushing and broach and shoved it through with an arbor press, then cleaned the chips, put the shim between the bushing and broach and did it again. It made a perfect 3/16" keyway the first time.

If I had to do this at home where I don't have that nice broach set, I'd do it in the lathe after reaming. I'd put the lathe in the lowest speed setting to prevent the chuck from moving during this power off operation. Then I'd grind a HSS tool and push it through with the carriage feed screw by hand advancing after each stroke until the keyway was the right depth.

I then put the pulley in the drill press vise, lining the top of the keyway dead center on top and drilled for the setscrews. I drilled all the way through both sides (with the proper size bit for the tap I was using) so the 2 setscrews would be on opposite sides for balance.

I started the tap while the work was still in the vise, using a homemade dead center in the (power off) drillpress chuck bearing down on the top of the tap handle to assure a straight thread as I started it by hand.

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