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davidh
03-05-2011, 12:45 PM
I am going to attempt to replace the hp three phase motor on my ace grinder with a single phase hp one.
The obstacle is the shaft size. The old motor has a 5/8 keyed shaft and the new motor has a shaft with a flat for a setscrew.
I have turned and bored an adapter that will make up for the diameter change but the question is:
should I attempt to cut a keyway slot in the adapter and make a modified long key so it will sit right over the flat on the new shaft or should i just drill the adapter and drill and tap the pulley with a couple setscrews thru the adapter at the area of the flat on the shaft ?

i think i can silver solder the adapter to the small shaft with a carbon clamp plier that i use to make battery cables, so a o/a torch would not be necessary and the silver soldering would only need to be a little bit to hold the adapter onto the small shaft.
This grinder is only turning a 3 hi speed wheel so the only torque on the pulley is at startup. . .

Bill McLeod
03-05-2011, 12:51 PM
cutting a keyway will end up cutting through the adapter and you end up with a curved shim, done lots and they work pretty good for me, a bit of playing around to spread the thing and get the key but works Ok

vpt
03-05-2011, 12:54 PM
Sounds like a good idea to cut the keyway threw the sleeve and into the shaft and key the whole deal. If possible I would maybe but at least one set screw threw the pulley into the backside of the key itself. So when you tighten the set screw you will be locking down the keyway, pulley, and sleeve so nothing can move around at all.

If you are close to Stevens Point you can run the motor over and I can tig weld the sleeve on if you want as well.

digr
03-05-2011, 08:19 PM
The 1/2" shaft must be stepped down. If so you could press it out and make a new one.

darryl
03-05-2011, 08:31 PM
Since you're going from 1/2 to 5/8, a piece of sheet steel 1/16 thick would have made the proper thickness of shim. I probably would have rolled a piece of a length to be just short of pinching the key- for a 1/2 inch shaft with a 3/16 key that comes to a length of 1 3/8 or so.

Don Young
03-05-2011, 09:16 PM
I would not weld or otherwise permanently attach the bushing as doing so will make it impossible to remove the shaft from the bearing in the future. It is also not necessary, in my opinion. If everything fits snugly, a setscrew thru the bushing slot and against the key should be adequate.

Mike Burdick
03-05-2011, 09:29 PM
Make an adapter that has a larger collar on it near the motor housing for the setscrew like the following photo. Bore a 1/2" hole thru its entire length.

http://www.covington-engineering.com/images/LSAR35.gif

SGW
03-05-2011, 09:38 PM
You may be better off not replacing the motor. Grinder motors are often balanced and are big buck$. If the current motor is balanced and you put just a garden-variety motor on there, you'll get more or less vibration and not as smooth a finish. I suspect this would be especially true if you add a not-perfect adapter to the motor shaft.

I think I'd buy a VFD and run your current motor.

Carld
03-06-2011, 12:16 AM
I am thinking the same thing as Don Young. Just drill through the sleeve and use a set screw against the flat on the shaft. That will work just fine.

Arcane
03-06-2011, 05:28 AM
You may be better off not replacing the motor. Grinder motors are often balanced and are big buck$. If the current motor is balanced and you put just a garden-variety motor on there, you'll get more or less vibration and not as smooth a finish. I suspect this would be especially true if you add a not-perfect adapter to the motor shaft.

I think I'd buy a VFD and run your current motor.
Best solution by far.

derekm
03-06-2011, 08:26 AM
Best solution by far.
another vote for this, if the 3 phase motor is ok this is the best solution. a 1/2hp VFD can be had for less than 100 on ebay. A VFD driven 3 phase is a much better beast than a single phase motor.

davidh
03-06-2011, 11:05 AM
thanks for all the comments.

i did make the adapter, reamed to 1/2" id, then i used a 3/16 keyway cutter and slit it end to end on the bridgeport. it came out nearly perfect. i gently tapped it on the new shaft, set the orig. 3/16" key in place over the flat area of the shaft and measured, then gently tapped the pulley into place followed by tightening the orig. setscrew in the pulley making the assembly complete. im impressed, it had zero runout on a 4" pulley.

then i was looking at the nametag on the orig., motor, 3 phase, 220/440 reversable motor, etc etc. 3450 RPM what ? ah crap.................
my replacement motor is 1750 RPM (the operation was successful but the patient still died)

well i didn't get around to making modified motor mounts anyway. that would have wasted another couple hours plus a trip to the hardware store.

"the best laid plans of mice and men............................................."

i am going to buy a vfd for it i guess. . . . .

wonder what i can screw up today ? ? ? ? ? maybe try to replace the thermostat in my MR2 toyota if i can find where it is. . . . .