Control Sheave Bearing Repair

[redleg]

A lot of good ideas for repair of control sheave bearings have been presented on this forum. This is my latest idea on the subject. I don't have any before pictures. Here is the finished repair. All the pieces to the control sheave were present but it had a serious crack and the bearing was shot. I don't have a bad headstock to put this back in but it looks like it should work ok.

3/4" copper coupling

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A 3/4" copper coupling fits snugly over the control sheave. I cut the coupling 1/8" longer than the control sheave shaft, drove it on with a block of wood, and peened the copper over the bearing outer edge. Don't forget to mark where the lube hole is and drill it. Look for a cheap coupling that is thin walled without the center ring indent. While the full ringed indent version may work it was not the one used. If I find another control sheave to do I will put the copper coupling over the shaft before removing the bearing to see if that will eliminate the cracking.

[br549]

That's looks like a very ingenious solution. Having just repaired mine using JBWeld, I would have tried this first if you had been a few weeks sooner. And I definitely like the idea of slipping it over the shaft before trying to remove the old bearing. Please keep us posted if you are able to try that on another one.

[reible]

Interesting idea. I really don't have a use for it now but I hope I can remember it if I ever do.

I too would like to hear some use related experiences after the repair.

Ed

[everettdavis]

You can help strengthen the sheave bearing mount area by tightening an automotive hose clamp around it before removing or reinserting the bearing, before you stake it.

[JPG]

Will have to try that on the fractured Mark VII control sheave. All the pieces are there, they just do not want to stay together.

[redleg]

I had four old control sheaves hanging around the shop from repairs of around twenty headstocks. Two were cracked, repairable; one missing a piece of the area around the bearing, possibly repairable with the copper coupling and JB Weld; on the fourth the inside shaft was completely worn out. These bearings have to be oiled to survive. Be aware this is a one time repair if the bearing goes again the copper coupling will not come off.

Manufacturing tolerances either with the control sheave or the copper coupling may be an issue with this repair. The first sheave went on fairly easily but still tight. With the second one yesterday I had to get a bigger hammer. It was really tight but did go on. Sure would be nice to have a press.

If I remember correctly a Mark V control sheave works on a Mark VII by replacing the bearing and loop from a Mark V control sheave with a new bearing and parts from the old Mark VII control sheave. Check that outer diameter on the old Mark VII control sheave before you buy a coupling.

[JPG]

. . .
Check that outer diameter on the old Mark VII control sheave before you buy a coupling.

But of course!

I think the length of the 'snout' varies.

[everettdavis]

Now that has me wondering if I might could fabricate a cap by using a 3/4" Copper Cap, drilling a hole in it, and using my hydraulic cable crimper to snug it in place.....

Everett

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.75 inch copper cap.jpg (16.4 KiB) Viewed 11056 times

[redleg]

Everett I was going to post the 3/4" end cap but was working on the part that holds the bearing first. I made a couple out of 3/8" bar stock but only one turned out decent. I switched to a 3/8" bolt and turned it on the metal lathe and I think it will work great.

I think the end cap will work fine as is. I drilled a 5/8" hole in the end cap. My thought was to drill two opposing holes in the sheave just deep enough to set the copper into with a punch. You may be able to use the cable crimper but be careful not to put to much pressure on the bearing.

Sheave Replacement Parts For Shopsmith (960x1280) (768x1024).jpg (289.79 KiB) Viewed 11044 times

[everettdavis]

Thanks for the follow-up.

My notion was not to put any pressure on the bearing or the bearing mount but to back away just a bit and crimp the area about 1/4" shy of the end of the sheave.

One thought was to pre-crimp the cap forcing it to compress slightly, then press the cap over the end of the sheave which would be a few thousandths proud of the cap circumference.

That would keep all compression pressure off the sheave. One could use stud and bearing mount on the sheave area the cap pressed onto, and still remove that copper cap at a later date gently with a die grinder, to service it in the future.

I like the cap approach as it leaves the oil hole out of the equation.

The neatest thing about this approach is that someone could offer the bearing, the button, and a pre-compressed cap etc. in a service kit and all users would have to do is remove the old and press on the new.

Everett