Control Sheave Button Bearing

[br549]

Yesterday I started getting an unusual sound and vibration in the speed control dial while doing some disk sanding with speed set on "SLOW". I think the button bearing in the end of the control sheave is the culprit. When I looked inside the inspection port, the retaining clip had become unconnected from the bearing, but was still around the porkchop spring clip. As I rotated quill by hand, the center of the button bearing was "wobbling" up and down as it rotated.

I took it apart this morning enough to get the control sheave out (after reviewing many other posts and Sawdust Sessions to refresh my memory on how). I think the button bearing is still "intact", just very much off center with the shaft, very hard to turn. No damage done to the spring clip on the porkchop as I caught it early.

Is the button bearing itself replaceable, or must I get an entire new control sheave?

[wa2crk]

The bearing can be replaced. There is someone on E-Bay that advertises sheave rebuilding service but you would have to do a search for him. The bearing is staked into the hub and I have only replaced one and I used a punch to tap out the stakes in order to remove the bearing. It is quite easy to crack the shaft when replacing that bearing. Bill Mayo on this forum knows the number of that bearing
and may be able to advise you. It appears from the rear photo that the key slot may be worn oversized due to the wobble. If it is then a new sheave is required as well as a new key. Also the bright marks on the points of the sheave vanes and the chatter marks on the hub indicate excessive wear.
Bill V

[ChrisNeilan]

Not that hard a fix. You can get the bearing here: http://m.ebay.com/itm/REPAIR-YOUR-SHOPS ... Ciid%253A1

[br549]

Thanks to Bill and Chris for your replies. Decided to just replace the bearing/button assembly at this time. Ordered one from bandsaw-tire-warehouse using the link provided. Would have liked to have been able to just buy the bearing (which with a flashlight and magnifying glass looks to be a 635Z), but had too hard of time getting the bearing out of the shaft to make me think I would be successful in re-attaching the button to a new bearing. I finally got the outer race out of the shaft, but not without a little minor chipping of the end of the shaft. In the process of re-attaching the chipped pieces and reinforcing end of shaft with JBWeld. Haven't tried removing inner race which is still on the button, but will just for fun. In the picture the face of the sheave looks worse than it feels, so hopefully it is not worn too much and will still work OK. Will post a final result after I get new bearing/button installed.

[wa2crk]

br549
Make sure that the inside of the shaft is clean and smooth. No JB weld in there!!! The button has to be staked in the bearing inner race and when it is removed it is difficult to salvage enough of the previously staked material to have a secure assembly so work carefully.
Bill V

[JPG]

GOOD LUCK!

Having attempted a similar task(although likely more severely damaged Mark VII ) I cannot offer encouragement.

Worth the effort though!!!!

[ChrisNeilan]

When I did mine, I chucked the sheave up on my Delta midi-lathe and trimmed the end of the sheave with a square carbide lathe tool. That cleaned up the face so that I could then stake the bearing with a punch. Work out well for me.

[JPG]

Fractures are what to avoid. Especially when removing the original bearing.

[ChrisNeilan]

Fractures are what to avoid. Especially when removing the original bearing.

Correct. I wish I could remember how I drove the old bearing out. I think I used a socket and an extension and light rapping with a mallet. I may have held the sheave in my hand to absorb some of the shock.

[JPG]

I suggest a sleeve with an id close to the od of the 'snout'. Slipped over the snout so as to restrain any swelling.

Slow and steady(light tapping).