Loose Poly-V Pulley

[billmayo]

We were using a 2004 Mark V for boring a hole in 1 1/2" wood using a 2" hole saw. The hole saw got about 1" into the wood and stopped causing a loud metal squeal from the headstock. The headstock would not drive the hole saw any more with the motor operating. The Poly-V pulley was spinning free on the Drive Sleeve shaft. I removed the Drive Sleeve Assy and tried to tighten the set screw in the Poly-V pulley but it was really tight already. I remove the set screw and noticed that it is only half the length of the set screw hole in the pulley. Using my leather prick on my knife, I removed a lot of what looked like hard carbon from the hole. About a 1/4" worth of carbon(?). The set screw still would not go any further into the screw hole. I used a 5/16" bottom tap to clean the hole threads. Now I can lock the Poly-V pulley to the Drive Sleeve shaft flat but the set screw is about 1/4" deeper in the hole. Does anyone know what I removed from the screw hole and how it was to hold the pulley to the shaft (it didn't). I have added this to my list of things to check when repairing/rebuilding headstocks.

Bill Mayo

[Bruce]

In looking at the exploded view on the service parts web page, it looks like the set screw is part #513056. It is called a 'cup point set screw' in the part list. Just to be sure I'm correct, you're talking about the lower pulley on the motor shaft. Correct? I suggest you check out the parts list and diagram to verify my findings. BTW, the service parts 20% off sale is on until the end of the month.

Bruce

[Bruce]

There is also a key on the shaft (part #504209). That may be the 'carbon' like material you were seeing.

[charlese]

Bill - Hear is what I think happened - Your hole saw hit it's maximum cut and stalled out because the base of the hole saw had reached the surface of the wood. It just can't go any deeper than about 1 inch because it is not made to. I saw a "Martha" show not too long ago when she was showing how to bore a hole into a pumpkin. When the pumpkin was thicker walled that the saw was deep - - her hand held drill stalled and she couldn't saw through the pumpkin. She, of course, blamed the crew for not doing things right.

When your hole saw jammed - the strain in the SS broke the long key (or rounded the key-way in the fan sheave) so the sheave stayed still while the motor shaft rotated. The only set screw in either the Idler shaft assembly (the upper one) or the Motor sheave assembly (the lower one) is on the inside of the fan sheave. This has to be the one you took out.
My guess of the "carbon stuff" you found is iron dust and dirt from the moving around of the sheave on the long key and the shaft. Solution? Remove your Motor sheave assembly and inspect it for rounded key-ways and a rounded/broken long key. Then go from there. In the worst case (I hope) you can replace just the fan sheave the long key and the setscrew. Hope it is no worse than that.

Please excuse me if I am wrong in my assumptions here as I was trying to figure out where a set screw is located in the poly V belt "pulleys".
I Think you must be mistaken about the poly V belt pulleys as there is no set screw on either of them. The poly V belt is the flat wide one that has grooves on the inside. You tighten this belt with the eccentric bushing on the end of the idler shaft.

[billmayo]

This Drive Sleeve pully is a different design and the first I have seen. The set screw part of the pulley is 1/2" larger than the older Poly-V pulleys but the set screw is the same length. I talked to Shopsmith and they went to an one-piece shaft and pulley that eliminated the set screw about 10-12 years ago. Before that, they used a longer set screw with the larger set screw part pulley. They have no knowledge of or have seen my problem before. So hopefully, this was one of a kind problem. This is the top pulley that drives the quill. We was using a 2" deep hole saw for the 1 1/2" wood. There is no keyway on the Drive Sleeve Shaft. There is a key way on the Idler shaft that the Idler Sheave which has the lower Poly-V pulley as an integral part. The set screw is located under the headstock housing's last drive sleeve bearing part so it cannot be seen until the drive sleeve assy. is removed. The set screw was normal, it was just a 1/4'" short of contacting the shaft. It was not dirt, grease or metal that made up that 1/4" to the shaft. It was very hard and stained my fingers just like when I hand sharpen a pencil. It works now with the set screw a 1/4" deeper in the pulley set screw hole and is now contacting the flat on the shaft. I wanted to make everyone aware to check the set screw if they remove the Drive Sleeve Assy on older headstocks.

Bill Mayo

[swileysr]

When turning the quill shaft by hand, I could locate a particular spot about 1/4" wide where the shaft could turn back and forth, but the poly V-belt and the poly V-belt grooved pulley (the one on the top of the headstock) would not move, after that "spot" the pulley and the poly V-belt would again engage and all moved as one unit. I figured that there had to be a set screw there somewhere, although my parts break down in the Shopsmith owners manual page B-6 and the drawing in the separate Headstock service manual (publication PL-5316 6/91) page 11, figure number 24, did not indicate one. Sure enough, after removing the "drive sleeve assembly", there is one on my unit (I purchased new 14.5 years ago). It was not screwed down all the way, although it would not let the poly V-belt pulley turn independently on the shaft, it did account for the "backlash or slop" at that one point in its revolution. When I went to tighten it I noticed it turned hard, so I thought why did it V-belt pulley loosen? Upon removal of the setscrew I noticed some hard brown waxy material, once removed and cleaned, the set screw worked normally. I think the brown material may have been placed there, as a "locktite" sort of screw locker and maybe the setscrew was never bottomed out properly. Under certain stress conditions, perhaps a large "tool catch" when using the wood lathe? the brown material gave way to reveal the true length of the set screw. Anyway I intend to use Loctite when I screw the setscrew back into place.
On another issue, recently a fellow owner posted a note about removing the "play" or "wiggle" in his quill shaft when it was fully extended as in drill press mode, by using a .015 steel shim, super glued in place. I was hoping for some photo's and even wrote him an email (although the forum's email system is private, which means he would have to check it separately from a normal Internet account, I guess he doesn't very often) so does anyone know if he has photos? Thanks.

[charlese]

.....I talked to Shopsmith and they went to an one-piece shaft and pulley that eliminated the set screw about 10-12 years ago. Before that, they used a longer set screw with the larger set screw part pulley. They have no knowledge of or have seen my problem before. So hopefully, this was one of a kind problem. This is the top pulley that drives the quill......

Bill Mayo

Bill Thanks for posting your problem with the drive sleeve assembly. No wonder I couldn't find a set screw. Now I understand! From the last post others have had a similar situation. Guess we will have to agree with "swileysr" that the stuff under the set screw was put there to hold the screw tight.