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Re: AO Smith 3/4 HP Motor Rebuild

Posted: Thu Oct 10, 2019 9:37 pm
by JPG
Push the fan sheave back onto the motor shaft. Then visually examine the threaded end of gthe motor shaft to ascertain what the sheave is binding on. Gentle filing of those 'high' spotswill make removal easy.

Note the motor shaft does not have a 'dimple' and the key is straight(except where mashed by the set screw).

IIRC that motor bearings are both standard 6203 (17 x 40 x 12 mm).

Also IIRC only the Emerson motor uses a 5/8" id on the internal shaft end.

Re: AO Smith 3/4 HP Motor Rebuild

Posted: Fri Oct 11, 2019 1:46 pm
by chapmanruss
As has already been answered, your Shopsmith is a Mark 5 not Mark V. A little history may help in understanding this. The Mark 5 was introduced in March of 1954. It is the machine's model name as shown on the vent/serial number plate on the belt cover. After Shopsmith Inc. was formed in 1972 to restart production of the Shopsmith tools advertising and printed materials for the Shopsmith Mark 5 began using Mark V. Even the 1973 Owner's Manual, the first one under Shopsmith Inc., had Mark V printed on it. Around February 1980 the name on the vent/serial number plate changed to Mark V and only Mark V has been used since on the tool, printed materials and elsewhere. Until the introduction of the larger table system of the Mark V 510 (and 505) there was only one Mark 5/V model. The Mark V with the original table system became the Mark V 500. All Mark 5/V's made before the introduction of the Mark V 510 & 505 are a Mark 5 or Mark V unless factory upgraded to a Mark V 510R. I have never seen a reason given for the change from Mark 5 to Mark V. The difference between a Mark 5 and Mark V is the name only. There have been many changes to the Mark 5/V over the years but no apparent change was made at the time of the name change on the machine itself.

Re: AO Smith 3/4 HP Motor Rebuild

Posted: Fri Oct 11, 2019 2:40 pm
by johnkgerken
Hi all,

@chapmanruss, your history lesson helps quite a bit. Thanks for taking the time to write that out. And @everettdavis, you were absolutely correct. I checked the vent cover and sure enough, it says "Mark 5" right above the serial number.

JPG, I did as you suggested and pushed the fan sheave back down to uncover the marks I'd inadvertently made when trying to keep the spring compressed long enough to remove the nut. I sanded uniformly around the shaft using 120, 220, 320 and 400 until all but the indentations were removed and then the fan sheave and spacer came right off. This had the added benefit of making that part of the shaft all nice and shiny. ;-)

@everettdavis, I've ordered a new 504205 Spacer Sheave from ShopSmith. They don't seem to differentiate between motors in the exploded diagram and mine is different, since I don't have a washer and retaining ring holding the spring on, but hopefully, they are the same size.
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As you can see from this picture, my centrifugal switch, as well as the spinning brass part beneath it are quite different from the pictures in the AO Smith 1 1/8 HP thread. On my motor, the connecting wires are soldered on, so I'm going to have to remove that to get to the back bearing. Since I hope to switch out all the old brittle wires anyway, is there a replacement part that I should consider here with detachable wires to make any future work easier???

The spinning piece has a single spring, vs. the two springs in the later motor, but it came off the same way revealing the flat head screw. So that part came off without any issue at all.

Now back to the front, the cover now comes off and the bearing is held in the cover by a small plate. The plate came off by removing the two small screws to reveal the bearing.
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But there is no obvious way to use a traditional tool to remove this bearing. All I could find was a small space where I could push the bearing out with a flat head screwdriver. Not ideal perhaps, but it worked.
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Unfortunately, it damaged the bearing, but not to the point that I couldn't read what it said.

@everettdavis, here are the particulars that I've collected so far using my calipers. Am I missing anything?
  • Text on both sides of the bearing: HOOVER 77203 MADE IN U.S.A.
  • Diameter D = 40.01mm
  • Bore d = 16.87mm (0.663") (Not sure what to make of the non-standard size.
  • Width W = 11.98mm
  • Shaft = 5/8" (0.626"/15.91mm)
So then. I need a bearing where D is 40 mm and W is 12 mm. But what should "d" be? Would I select 16 mm, as it is slightly above the shaft size, but less than the current (very worn) bushing, or should I ask for a "d" of 5/8"?

Thanks, guys! I'm making progress one baby step at a time. I couldn't have made it this far without your help.

Re: AO Smith 3/4 HP Motor Rebuild

Posted: Sat Oct 12, 2019 10:25 am
by JPG
Look at the armature shaft. I think yours is .625 without any variation in the area the bearing goes.

So I think 5/8 "d" is appropriate. So 40 x 12 x5/8" .

Check the rear bearing shaft size the same way.

Re: AO Smith 3/4 HP Motor Rebuild

Posted: Sat Oct 12, 2019 12:34 pm
by chapmanruss
John you asked
Since I hope to switch out all the old brittle wires anyway, is there a replacement part that I should consider here with detachable wires to make any future work easier???
I would just replace the wires the way they are instead of trying to put something in there that may or may not fit well to make the wires detachable. Look at it this way, it has lasted almost 65 years so far and with the work you are doing the next time something needs to be done to the motor may be another 65 years or a motor rebuild/replacement.

Re: AO Smith 3/4 HP Motor Rebuild

Posted: Sat Oct 12, 2019 6:31 pm
by everettdavis
The tool you can use (opposed to knocking it out with a Screwdriver) is a Blind Hole Pilot Bearing Puller. In a bind hole, you could not get to the back side of the bearing. Some models of some motors have blind bearings.

I just borrowed one from an auto parts store last time I needed one.

The adapter goes inside the bearing then expands on the back side. The slide hammer then evenly pulls the bearing out of the housing.

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Re: AO Smith 3/4 HP Motor Rebuild

Posted: Sun Oct 13, 2019 11:42 am
by JPG
Back in the days of manual clutch transmissions, that was called a pilot bearing puller. The pilot bearing was imbeded in the flywheel.

Note it requires pressure be applied to the inner race to pull out the tightly fit outer race. Hence should only be used IF the bearing is to be replaced.

Re: AO Smith 3/4 HP Motor Rebuild

Posted: Mon Oct 14, 2019 3:45 pm
by everettdavis
I had to remove a pilot bushing from a flywheel and didn’t have one. My late uncle snickered at me, brought out his grease gun, filled the inside of the hole behind the bushing in the crankshaft, pressing it full. He then inserted another shaft the size of the transmission shaft into the end of the bushing. He took a large hammer and gave it a whack.

Out popped the bushing, forced out by the grease.

He just looked up and smiled at me. He said that’s how I do it. He had used the same part from a broken transmission that he kept so he could center up the clutch disk before tightening down the clutch plate. Now they give you a wooden alignment tool with the new clutch.

Back then, you did it with old shafts with the right spline.

I miss my uncle. He taught me so much.