Floating Sheave Is Stuck "Open"

[Duncan3]

Hi,

About two weeks ago I was using my 1955 greenie and, after turning it off briefly, when I switched it back on the motor ran but the spindles did not turn.

I opened it up and found that the drive belt was slack and the sheave was fully open (i.e., the flange halves were as far apart as they could get). Note that this is against the spring's compression. I managed to get the sheave halves free though it took some doing because they were jammed together some how. It worked for a while, but today the same thing happened. Since it appears to be a recurring problem I have come here seeking advice instead of doing the same thing again.

This is what it looks like. Anybody seen this happen before?

20260722_103234.jpg (378.72 KiB) Viewed 210 times

Thanks,
Duncan

[Duncan3]

Hi,

Since my original post I done a little more.

First I more closely examined the sheave half positions as shown in the first picture. Clearly the key is not doing its job. I managed to get them realigned into the norman position.


I made a spring compressor and examined the end of the shaft. Though the 1955 manual indicates a nut on the end, there is a retaining ring.
It is in the second picture below. I do not know how to get a ring like this off without risk of destroying it. Is there a tool for this style.

If I can replace the ring and cup with the newer ring and washer, I'd be OK with that and wouldn't worry about the old washer. Does anyone know if the current ring will fit the 1955?

Also, since it is apparent that I need a new key, I looked for it on the Shopsmith.com parts page and it comes up "404 not found." Is this part available?

Thanks,
Duncan

[HopefulSSer]

To remove the ring, put a small screwdriver under the recess circled and gently pry it out & up. You can then carefully unwind the ring by prying up on it as you walk around the shaft. Installation is essentially the reverse.

Screenshot 2026-07-26 at 9.57.28 AM.png (1.46 MiB) Viewed 214 times

As for the key:
https://www.shopsmith.com/product-page/ ... headstocks

The description in the exploded diagram says "for 1-1/8 hp motors". Unless it's been changed, yours will be 3/4 hp. You might contact SS to confirm it's the same. It probably is, but best to ask.

[GetterDone]

Here is a link for the key below.

Link: https://www.shopsmith.com/product-page/ ... headstocks

If you use a seal pick and 2 thin blade screwdrivers you should be able to remove the snap ring without damaging it.

I use the seal pick to pry it away from the shaft using the little tang on the end of the snap ring.
Then put the screwdriver blade in the gap and work it out of the groove.

Hope this helps.

[chapmanruss]

Duncan3,

Welcome to the Shopsmith Forum.

HopefulSSer and GetterDone have already given you some information about dealing with the type of retaining ring used on your motor shaft. Motors used in the Mark5/V over the years have been made by a number of manufactures in both the early 3/4 HP Motors and the 1-1/8 HP Motors which they changed to in March 1961. Along with that there have been different ways the Spring has been held on the Motor Shaft. These are not necessarily interchangeable. Your idea of replacing the Cap with a washer could work fine as long as the ID of the Washer matches the OD of the Motor Shaft. The reason the Manual does not match what you have could be the Motor was changed or the Manual is not the original one for your Mark 5. There were 3 different version of the Manual in 1955.

[Duncan3]

OK,

Using the help I got here I got the ring and spring off. The first and second pictures show what I found -- the key broken out the side of the floating sheave. So, that's a problem.

I found the key broken through the side of the floating sheave.

20260726_122604.jpg (104.09 KiB) Viewed 187 times

Broken floating sheave.

20260726_123303.jpg (175.45 KiB) Viewed 187 times

I also found that the fan sheave was smashed down against the motor plate and would not turn. This was not the case yesterday, so I can only think that I drove it down while removing the spring. (Pictured below.)

Fan sheave against the motor plate.

20260726_123356.jpg (431.02 KiB) Viewed 187 times

When I removed the fan sheave, I found what I think is the sheave spacer jammed down into the motor plate with about 3/32" showing. pictured below. Is that what I'm looking at?

Sheave spacer

20260726_130210.jpg (252.58 KiB) Viewed 187 times

As a minimum I need to replace the floating sheave and key, and I'd replace the fan sheave while I'm at it. But, is there a way to fix the apparent spacer problem? Do I have to replace the motor? Headstock?

Duncan

[gleno]

You'll need to polish the shaft before you put the new sheave on. I would also put new bearings in the motor if I was that far into it.

[chapmanruss]

If the Motor is the original 3/4 HP Motor and you are considering replacing it, I would recommend looking into that first. A replacement may have some or all of the Motor Pulley parts included. A new Motor from Shopsmith, although currently listed as unavailable, does not come with any of the Motor Pulley parts. A used one may have some or all of the parts needed. Used Motors are commonly found for sale online as owners upgrade to the Power Pro DVR Motor. The Sheaves, Key and Spacer are all currently available from Shopsmith. Since these are not parts I have had to replace on any of the Mark 5/V's I have owned/restored I cannot confirm if the current parts are all compatible with the early Greenie Mark 5's with the 3/4 HP Motor but I believe they are. Hopefully someone else can confirm.

[chapmanruss]

The replacement parts (with Part Numbers) mentioned are the Fan Sheave P/N 504207, a Set Screw P/N 513016 (for the Fan Sheave), Floating Sheave P/N 504208, Sheave Spacer P/N 504205 and the Long Key P/N 504209 which in total cost $111.75 plus shipping, new from Shopsmith. The original Fan Sheave Set Screw may be able to be used again. Hopefully the Spring and Spring Retaining parts are still usable.

You can use the above information in considering if buying an upgraded replacement 1-1/8 HP Motor would be a good idea. For part of that consideration, I would recommend running the Motor you have with the Pulley parts off to see if it still runs okay. Start with turning the Motor Shaft by hand to see if it turns freely and smoothly then with power.

[Duncan3]

Russ and gleno,

Thanks for the input.

Following the suggestion I just turned on the motor and it runs fine.

I think that changing the motor bearings and polishing the shaft are good ideas, but beyond my skills and equipment.
At this point I'm weighing the possibilities of replacing the headstock. Despite the sentimental aspect of my father's Shopsmith, I've experienced a couple of failures in recent years that shut me down for a week or two. I doubt it is going to get better.

Looks like I can get a used later model with 30+ years less wear and sexy features like an access port, 1 1/8 hp motor and dual bearing quill for a few hundred dollars.
If I go to Shopsmith for a new one, seems I might as well go for a Power Pro for $3k vs conventional for $2k.

Meanwhile, I took a closer look at my 1955 manual and I see that it does not show a spacer. I guess it was always held in place with just the set screw. Is that possible? Did I drive the fan sheave down onto the motor plate when I compressed the spring?

Duncan