Making the shaft hole in a pulley larger

[Mike Cruz]

Anyone see an issue with making the shaft hole (sorry, maybe not the correct term, but you know what I mean) in a multilple pulley larger...from 1/2" to 5/8"? I wouldn't do it myself. I would take it to a machine shop to make absolute sure it was straight. But do you think that it might upset the structural integrity of it? I can't imagine it would, but...

The story behind this is that I just got an old (1947) Delta lathe. The motor on it was a replacement 1/3 hp dual 1/2" shaft motor. I am upgrading that to a 1 hp with a 5/8" shaft and would like to reuse the multiple pulley, rather than having to buy a new one.

On a side note, I couldn't easily find multiple pulleys. Anyone know where I can find them at a reasonable price? Thanks.

EDIT: Ok, I just found some on Ebay...don't know how I missed them before... But the question still stands about redrilling this one.

[Kyle Iwamoto]

The key way must also be machined. Buy a new one, it may run you less money.

[Bruce Page]

Grainger sells them for as little as $21.10

[Mike Cruz]

Common Bruce, there has to be someone out there with a metal lathe or a fancy metal DP that is willing to do this for me! Hehe...

Yeah, after finding some on Ebay, I saw the key issue. I wasn't thinking about that since the old motor has a flat spot and set screw. I'm sure the new motor will have a key...

Thanks guys.

[Steve knight]

enlarging the hole is not hard if you use the right tool. a chucking reamer will do it with just a drill press. but it would take two or three of them to get to that size so you would be better off buying a new pulley.

[zayd alle]

Mike,

Definitely have a machine shop do it. Getting the grooves and inside diameter perfectly concentric is critical for vibration-free operation. You'll obviously need to have them enlarge the hole and broach a new keyway.

As for structural integrity, aside from using your own best judgement, perhaps the machine shop can advise you. I need to have this done on my PM66 motor pulley with a 3/4" bore, but PM used the same pulley with 7/8" motor shafts as well, so I know I'm ok there.

I recently asked the same question over at OWWM. If you're looking to buy a replacement, there are a few key measurements to consider. See the post by GeeP:



Good luck with it.

[Alex Shanku]

I would find a 3/4hp delta motor, period correct, with a 1/2" shaft.

I would not try and enlarge the bore on that cast step pulley.

But thats just me.......

[Bruce Wrenn]

There probably isn't enough wall thickness to enlarge the bore. And most certainly not enough to cut a keyway. Buy a sheave from Grainger or others.

[Mike Cruz]

While I understand that removing stock (metal) would weaken the pulley to some degree, we are only talking about 1/8"...1/16" in any given direction.

Bottom line, though, is that the whole key thing (which I had not thought about) kills the whole idea. I would either need to accomodate for a key, or flatten out part of the shaft for the set screws on the existing pulley. So, I'm looking at a couple new/used step pulleys now.

[Ted Baca]

I think I would move in another direction here. Rather than enlarge the hole find a bushing or have one made that has a 1/16" wall thickness.
This would eliminate the concern on weakening the pulley. Maybe one at ACE HDWE and probably less than 1.50. Another option if you have a drill press is buy a short length of 5/8" barstock and drill a 1/2" hole in it. Just drill slow and keep it cooled with cutting oil and you will waind up with a sleeve that will work. But the bushing will exist if you just look at hardware stores or bearing parts houses. In colorado we have Rocky Mtn. Bearing for example.

[Clarence Miller]

In projects like this I will usually take the part to the local machine shop and ask the machinist with the most grease on his clothes if it would be a feasible idea. If there isn't anyone with grease on their clothes I look for the one with the grayest hair.