7/8" motor shaft, 16mm pulley bore. What do to?

[J Tiers]

The problem with modifying the motor is not the process (that's easy), but that you are dooming yourself to having to do that again when you replace the motor. Motor sizes go with certain shaft sizes.

Making a "special" once means that there is likely no other motor which you can find that will fit without modifying it. Now, next time you need to replace the motor (they do fail), you will not have a lathe (dead motor) and will need to modify the shaft or pulley again.

Using standard stuff whenever you can means less trouble in the long run.

[Doozer]

Another perspective is design and maintenance.
On one of my lathes, it has an 8hp motor.
I had to take it apart because a mouse had gotten
inside and I wanted to check the windings for
mouse damage. Dreadful creatures.
Anyhow, I had to take the pulley off the motor shaft.
It was a 5 belt pulley and the shaft was 1-3/8" with
a key. Pulley was a standard affair, secured with
a set screw.
Well let me tell you, I had a 15 ton 3 jaw puller and
I worked my azz off to remove that pulley from the
motor shaft. The puller alone would not take it.
I had the oxygen acetylene torch applying heat to
the pulley, bring it to a dullest red. I would heat and
then turn the wrench on the puller, then hit on the
puller screw with my 3 pound copper hammer to get
the pulley to move. I made head way about 30 thou
at a time. It took 2 hours and a bunch of acetylene
to get that pulley off. I might have been better using
an impact wrench on the puller screw, but I think that
might border on tool abuse. It was an Enerpac puller
but I don't think the screw was all that hard. So I kept
with the hand wrenching and applying molly lube to
the puller screw threads.
Anyhow, I was successful getting the pulley off the
motor shaft. Plenty of that red fretting corrosion.
Set screws and keys are a miserable way to attach
hubs to shafting. Not wanting to fight that battle
ever again, I bought a QD (quick disconnect) taper
lock bushing type pulley. QD bushings bolt in and
bolts also drive them apart for easy withdrawal.
While I was at it, I got a little larger pulley to increase
the speed of my lathe. I think I want from 850 to 1200
RPM top gear speed.
No I am not worried about the belts slipping,
No I am not worried about the headstock exploding
No I am not worried about the bearings melting
No I am not worried about the chuck falling off.
So yes the mouse had chewed some of the fishing line
that ties the coil wraps. I also took the opportunity to
clean the inside of the motor (filthy) and I bought some
Glyptal to paint the windings up pretty. I put some
shrink tube on the leads to make sure I would have
no shorts. I washed out and re-packed the bearings
with synthetic grease and painted the motor since it
was now clean.
But yes, the QD taper lock pulleys are the way to go.
Easy on and easy off. I think I paid a little over $200
for the pulley and bushing, only so expensive because
it was a 5 belt pulley. But in my mind, money well spent
to avoid ever having the fretting happen again, or the
other extreme, having it not stay tight on the shaft.
Best of luck.

-Doozer

[wmgeorge]

Doozer, yes it was Browning Taper Lock we used... never had an issue even without a keyway.

[CarlByrns]

The November/December 2011 issue of HSM has an article about pulley hub repair/replacement.

[old mart]

The 3/4" compromise looks interesting. Also, you may be able to get a pulley pair which has a slightly bigger diameter with the larger hole, as long as there is room in the casing. There is no substitute for having gears/belts for speed control, don't get lazy like many VFD users who would prefer to spend money rather than bother to change speed manually. Having the bigger motor and being prepared to actually change speeds manually is a bonus adding versatility.
When I changed the Tom Senior Light Vertical mill from MT2 to R8, I changed the motor from a 1/2hp to a 1hp with a VFD, running from 25-75Hz, the 4 speeds by belt are still essential for a good spread of speed and torque.

[Randy]

So there are several votes for Option Δ, make a new pulley. I like it. I'm pretty sure I can simply copy the principal dimensions from the original, but not cut the V-groove so deep. On the original pulley, the inside of the belt clears the bottom of the groove by .15", so I can leave quite a bit at the bottom of the groove in the new one, have plenty of wall thickness between the groove and the bore, and still be sure the belt doesn't bottom out. Taper-lock hubs are cool, I've encountered them before, but for my purposes I'm sure a conventional key and setscrew will plenty adequate. I guess I'll be calling my local Metal Supermarket for a hunk o' stock. (Unless one of you has a 2" length of 3.5" Ø steel you want to send me.) The original is cast iron, so I'd be inclined to use steel for a new one, but aluminum would be suitable as well, don't you think? It may depend on what I find in the remnant racks. Thanks, guys. That's what I came here for.

[wmgeorge]

Big mistake not making the V belt grooves as wide and deep as the OEM, but heck you've discarded a lot of excellent ideas already so go for it.

[Randy]

About the power: the OP is not expecting to use the 1-1/2hp, rather to get better power at reduced frequency. Where his current 3/4hp might fall to an unusable 3/8 at some frequency, a 1-1/2 falling to 3/4 & all be well.

Exactly. As another Jet 1024 owner I figured you'd understand my aim. As for overpowering the machine, I don't think so. Most references to this class of lathe that I've seen show a 1 or 1.5 HP motor. And while I'll probably never call on it to provide that much, I don't think it's inappropriate. The 1024 is a pretty stout little machine.

[Randy]

Big mistake not making the V belt grooves as wide and deep as the OEM, but heck you've discarded a lot of excellent ideas already so go for it.

Seem to me, as long as there' s clearance under the belt, such that only its flanks contact the pulley, that's all you need.

[chipmaker4130]

Belts 'wear in' to some degree. I'm sure you could reduce the clearance, but deciding how much might be difficult.

[wmgeorge]

Seem to me, as long as there' s clearance under the belt, such that only its flanks contact the pulley, that's all you need.

Belt pulleys are made the way they are for a reason....and to account for wear and transfer power.

[Richard P Wilson]

Yes, wear will gradually reduce the gap, but providing there is a gap, the drive will work just fine. OK, it might mean changing the belt more often say every 2 years instead of every 5 years, but thats not a big price to pay is it?