Modifying pulley on mill/drill

I recently purchased a new 3ph motor with VFD for my RF-31 clone mill/drill. The new motor is a 2 hp Marathon with a .875" shaft using a .187" key. When I took the pulley off the original motor I discovered that it had a 24mm shaft with an 8mm key (for some reason I had thought it was going to have a 17mm shaft). The 4 gang pulley is made of cast iron. Should I bore the pulley to 1" (or so) and press in an insert? If so, would I need to key the insert or would just pressing in or Loctiting the insert work? Any suggestions on how to proceed would be welcome.

Thanks, Phil Teague

Reply to
Phil Teague
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You do need to key or otherwise constrain the insert from turning otherwise you will quickly have a freewheeling pulley. Making a bushing where one side of the bushing is held in place by the pulley key and 180 deg. from there is the key for the shaft is probably the best way to do this.

-- Why isn't there an Ozone Hole at the NORTH Pole?

Reply to
Bob May

When I had to bush a pulley I made the bushing and then completely cut away the keyway. Then I machined a taller key that rode in the keyslot in the original shaft and seated through the bushing into the pulley. It's been working fine for quite awhile now.


Reply to
Grant Erwin

I've done something similar -- but for what you have, I see only a wall thickness of 0.0349" (after some calculator work to mix the metric and inch dimension).

For *that* I would suggest some 0.035" shim stock wrapped around the shaft, and touching the key on both sides. You'll need to start out with some key stock to fit the larger of the two keys, and mill (or file, if you can't use the mill at the moment) a step on it so it fits both the keyways nicely.

I had the advantage of needing the same width of key on both sides, and of having another mill to make the necessary cuts in the bushing -- which has a slot slightly shorter than the bushing, so the bushing is captive on the motor shaft.

In my example, I drilled through the key in two places, and installed a 2-56 (or was it 4-40?) SHCS in each, with the key counterbored to accept the heads. This keeps the key from sliding out as you mate the pulley and the shaft, leaving only the shim stock to control. If you have some time, make an expanding plug the size of the motor shaft, and loctite the shim stock to the ID of the pulley.

Hmm ... Perhaps bend the shim stock into the key slot, and trap it with the screw-secured key, so it is all a single piece to slide into the pulley.

Good Luck, DoN.

Reply to
DoN. Nichols

I'd just buy another cone that would fit. The exact ratios won't be there but will be close. I doubt the VFD RPM number (if it had one) would match anyway.


Reply to
Martin H. Eastburn

Thank you all for your responses. I have just about completed the setup of the VFD and now will tackle the pulley issue.

Phil Teague

Reply to
Phil Teague

I put a nice 2HP motor and VFD on my jet mill drill. I had to bore the pulley to match the motor. After several years of use, I find that I only use about 3 different belt combinations. I use 800RPM most of the time. I use a slower one for flycutting and maybe a faster one for drilling tiny holes.

SO if you have the typically 12 speed model, maybe you can just put a single pulley on the motor and use the second set of pulleys to give you some adjustment range.


Reply to
Charles A. Sherwood

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