View Full Version : How to dismantle electric motor?

12-28-2008, 01:18 PM
This time I'd like to avoid my normal motor repair process of procure/evaluate/teardown/cuss and throw in the scrap heap due to irreparable damage during the teardown process. Anyone here have any tips on safely dismantling this little pool pump motor? It's 115V/12A 3450 rpm and would be perfect for making a little polisher for my shop.

As you can see, the shaft is severely corroded but other than that, it runs perfectly. I'd like to get the armature out and get it into my lathe between centers to turn it down & fit a sleeve.


There's a centrifugal switch assy in the view shown below and the mechanical bits appear to be a permanent part of the armature. I tapped the other end loose from the case but the whole assy is moving back & forth but stops about 1/8" out.


The centrifugal sliding ring appears to engage the switch/terminal unit but looks like the whole armature/centrifugal unit should slide out the other end, leaving the switch/terminal in place.

The shaft on the terminal end of the motor has a slotted cap that's larger than the shaft itself so that must be what's keeping the shaft from sliding out of the bearing on that end? It's already boogered up from someone else's work so I'm guessing it has to come off.

Any ideas which direction the cap turns to remove it? I've got to make a flat blade bit to go onto my little 3/8" impact wrench to get it off.

12-28-2008, 01:33 PM
I would guess that it is a screw holding the shaft in the bearing as just as you think. Have you tried to seperate that end cap from the main housing? Maybe the end cap and armature come out together. That would stand to reason as it may have to be assembled out of the housing and installed as a unit.

12-28-2008, 02:24 PM
Thanks Carl. I modified a flat blade impact bit to fit the slot nice & tight and hammered away at it but I don't think it's a removable part. I'm thinking now it was put there to aid in freeing up a stuck pump.

There's some burrs on the o.d. of the shaft where it's boogered up and that looks like what's stopping it from sliding through the bearing. The shaft metal is soft as heck so I'm going to scrape off the burrs and give it another try.

Bob Ford
12-28-2008, 02:40 PM
The wires in the end bell go to the stator windings. The armature removes toward the pump end and then you can remove the end with the start switch. It is probably a little late, but normally the stator and end bells are marked before removal. 1 center punch mark on shaft end and 2 marks on end bell end. This assures that they go back together the same as they came apart.


12-28-2008, 02:54 PM
Thanks Bob. Yup, I marked the ends & case very clearly.

It turns out the burrs were what was keeping everything from sliding out from (as you said) the pump end. Once the burrs were gone, it slid out easily.

Glad I deburred it since that end has a bushing instead of a bearing and would have been gouged badly if I'd just driven it through. I was pi$$ed off it was made so cheap but upon further checking, it's still a great fit. I'll clean & lube it up and expect another zillion hours out of it. Not much load on that end anyhoo! The pump end sealed bearing is smooth and free...good to go.

Now, off to the lathe to turn down the shaft. Would 5/8" be a generic shaft size for your basic cotton buffing & polishing wheels?

12-28-2008, 03:05 PM
Look on MSC or Enco site because I think the OD of the wheel determines the ID of the hole.

Bob Ford
12-28-2008, 03:54 PM
Before you assemble things. The end bell with the start switch, The sheet metal cover over the bearing. If you can remove it without damage you can then re-oil the bearing packing. Spindle oil like you would use on a lathe.


12-28-2008, 07:02 PM
Just because I've been playing with tapers lately-

Why not turn a taper on the shaft such that you keep the threads and have clean metal all the way to the motor- then a matching taper on a sleeve that will hold the buffing wheel or whatever. Pulls up tight with the nut, no keying required, etc.

12-28-2008, 07:39 PM
I turned a .635" repair shaft with a .374" reamed hole, figuring I'd press it on with green Loctite and then turn it down to .625" once it was fully cured in its new home.

That done, I chucked up the armature in the 4-jaw, clocked it in & turned off all the corroded mess.


Question: How much interference fit would you give it - if any - taking the green Loctite into consideration? I'm thinking maybe as close to zero as possible, relying on the slight grooving from the lathe cuts to fill up with the Loctite.


12-28-2008, 08:22 PM
I think I'd be trying for a press fit and to heck with the loctite. Use hot and cold to your advantage.


12-28-2008, 11:11 PM
On the size of the mounting holes of cloth buffing wheels.

Thay come from 1/8th to at least 1/2 on the 8 in and smaller ones.

What a lot of the jewlers use is an adaptor to slip on the motor shaft.It has a 1/2 in hole to slip on the motor shaft,a set screw to hold it,is about 2 to 3 in long and the external part is shaped like a large wood screw.It is tapered from 1/8 to about 3/4 in with about a 10 TPI thread.if you made one the hole could be drilled any size to fit your shaft.(threads on right side need to be right,if used on left side of motor need left)

this is used because you need to have a wheel for every size grit compound you use.and it is a lot faster to change wheels on,thay just spin on and off.

12-30-2008, 08:54 PM
Thanks! My plan is to set it up with the 5/8" shaft turned down to 1/2" with a generic length to fit 6" and 8" wheels and their drive washers. Thanks for reminding me about thread direction/motor rotation.

Can someone that has a commercial polisher measure the length of the section of the shaft that's turned down to 1/2" and the length of the threaded portion? The local H/F store has one on display I could measure but it's way the heck across town. I need to be careful with my spare time...and gas usage.