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(06-03-2012, 09:41 PM)Tony Wells Wrote: The second shop I worked in did all the machine work for a nearby electric motor shop, so we got a lot of metalizing and shaft repair /replacement. If you wanted, for any reason, to maintain the original shaft, they are pressed in and can be removed and replaced with a newly made shaft of whatever size you want. Otherwise, a 4 jaw with pads, and a good bearing center is sufficient to turn it down. Watch that you don't reduce the seal area if the motor has a live seal on the shaft, and be sure to leave a 1/32" minimum corner radius where you shoulder out. And you may have to recut the keyway, or at least need to make a non-standard key.
If possible, boring the sheave/pulley would be preferable.
I have made pretzels out of perfectly good 1-1/2 diameter shafting by trying to press out the shaft from rotors. The shaft is pressed into a series of thin metal plates with an aluminium cages cast on the end, when you try to press out the steel shaft, the aluminium deflects and the thin plates wedge slightly side ways, then it gets really hard to press. A Bue gets built up on the shaft and wedges tight.
Turning down the shaft by gripping in chuck and supporting with ball bearing centre should work out just fine. Follow that with recutting a new key slot.
Walter
starlight_tools, proud to be a member of Metalworking Forum since Apr 2012.
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Well, I must have had The Force with me then. I've probably done 50+, from fractional to 150+ HP motors.I did use a support tube designed to clear the shaft, but fit closely. That way the lamination is supported. If the stack is allowed to "dish" at all, it will bite into the shaft, I would concur. I've just not had that problem. NEVER press against the fins/fan. They're usually riveted or peened in place, not cast that I've seen.
I was only offering that as a backup plan anyway. Turning it between chuck an center is the way to go.
In stead of replacing some of the mangled shafts that came in, we would cut off the end, drill it out to accept a stub shaft. 45° bevels all the way down, then weld up, turn and re-key.
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Just my 2 cents. Sometimes those shafts are loose and that's the reason they are being repaired. I do remember some defying my little press, assumed they were welded or fused in some manner. Never saw a hardened one that I know of.
Go for it. The motor will probably exceed the capacity of the pulleys/belts and squeal at startup and load, maybe even eat belts, but we'll never know if we don't try... :)
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(06-09-2012, 11:56 AM)Sunset Machine Wrote: The motor will probably exceed the capacity of the pulleys/belts and squeal at startup and load, maybe even eat belts, but we'll never know if we don't try... :)
Sunset,
Why do you say that?
The 3-phase motor I got is the same HP as the original single phase motor and I'll be using the same belt and the same pulley, if I decide to turn down the motor shaft.
Ed
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Guys,
When I get some time, I think I'm going to go for turning down the shaft.
Ed
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Ed, you'll be fine, keep us posted.
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(06-09-2012, 03:59 PM)EdAK Wrote: (06-09-2012, 11:56 AM)Sunset Machine Wrote: The motor will probably exceed the capacity of the pulleys/belts and squeal at startup and load, maybe even eat belts, but we'll never know if we don't try... :)
Sunset,
Why do you say that?
The 3-phase motor I got is the same HP as the original single phase motor and I'll be using the same belt and the same pulley, if I decide to turn down the motor shaft.
Ed
I went from a 1.5 hp single phase to a 2.0 hp 3 phase on my lathe with no problems at all. With the VFD ramping up the motor speed on start, it's not like you are doing a "hole shot" off the line with twice the normal torque output. 
Willie
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(06-09-2012, 03:59 PM)EdAK Wrote: (06-09-2012, 11:56 AM)Sunset Machine Wrote: The motor will probably exceed the capacity of the pulleys/belts and squeal at startup and load, maybe even eat belts, but we'll never know if we don't try... :)
Sunset,
Why do you say that?
The 3-phase motor I got is the same HP as the original single phase motor and I'll be using the same belt and the same pulley, if I decide to turn down the motor shaft.
I misread, thought you were hanging a larger 3 phase where a little single was. Anyway, turning the shaft down should be a piece of cake. Fitting a key will take longer. I'd ask if there are centers in the shaft, but at the risk of misreading posts again, I won't. 
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Ed, have we determined what source of 3 ph power you'll be using?
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(06-11-2012, 08:45 AM)Sunset Machine Wrote: I misread, thought you were hanging a larger 3 phase where a little single was. Anyway, turning the shaft down should be a piece of cake. Fitting a key will take longer. I'd ask if there are centers in the shaft, but at the risk of misreading posts again, I won't.
No harm done Sunset. I just thought I might be missing an important piece of information, it wouldn't be the first time. 
Ed
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