Power Pro idler hub

[GarthS]

I’m new to forum and after a few year absents from woodworking am now retired and ready to back at it. On my Power Pro headstock the idler shaft hub has crept somewhat into the belt cover. In fact I have to remove the vent plate to fully get to the set screw. Any ideas or suggestions?

[DLB]

I've never heard of that, but: Remove the belt cover, inspect where the idler assembly mounts to the casting. There should be two screws that limit travel in the outboard direction. The first screw is in the casting just above the idler and limits how far the eccentric bushing can travel. The bushing should be all the way against that screw. The second screw is in the fat part of the eccentric bushing and limits the outboard travel of the bearing and shaft. The bearing should be against that screw. I presume that one or both of these is incorrect.

Also inspect the belts. They should be perpendicular to the shafts, but probably are not in your case.

Check the position of the pulley on the motor shaft, it should be adjacent to a ring that limits its travel (also in the outboard direction). I can't recall right now, I think it is either a snap ring or an "E" clip. A 'common' failure mechanism on PowerPro is that the pulley setscrew loosens and the pulley may move on the motor shaft towards the motor and away from that ring. This might cause some inboard pressure on the idler shaft(?) causing it to move inboard in response(?)

Take pictures and post them here if you can. It is always easier to see the problem.

- David

[sehast]

Take a look at this thread. It happened to me too.

viewtopic.php?f=10&t=19567&p=229080#p229080

[GarthS]

Thanks for the advice.

I found it was missing the screw preventing outward travel and on top of that the upper belt has been rubbing against the headstock (I ordered a new belt because it is frayed on one side). The idler shaft and inside bearing had worked its way out of the bushing. I'm not able to find any diagarmas on SS website showing the layout so I'm questioning what prevents the bearing from migrating out of the bushing (to the inside)?

I'm attaching a couple of photos, bearing outside of the bushing is in photo #3 but it's hard to see.

[DLB]

I'm not able to find any diagarmas on SS website showing the layout so I'm questioning what prevents the bearing from migrating out of the bushing (to the inside)?

There is nothing that limits inward migration of the Idler on the PowerPro, unlike outward migration. Only the clamping force of the bolt and nut on the headstock hold the eccentric bushing and idler bearing. Because the eccentric bushing is the split type, the clamping force is meant to hold both the bushing and bearing. The Idler is not normally exposed to much outside force that would push it in, mating a Jointer or other lower aux shaft SPT is the only thing I can think of. (Sehast mentioned his headstock falling on the Idler, but that's abnormal.) The screws that limit outward migration are common to the conventional headstock, where the speed control mechanism exerts some outward force. Their only useful function on the PowerPro seems to be as an indicator of how far outboard the Idler should be positioned for the upper belt to be in alignment.

I had a conventional headstock missing the same screw and washer yours is missing. It was about 20 years old and it was obvious that the hole had never been threaded. Obviously not part of the problem you experienced. It is a 'thread cutting' pan head machine screw, 1/4-20 IIRC, maybe 3/4" long.

- David

[GarthS]

Thanks David. I pulled the missing screw from an old broken headstock a guy gave me so will install it when I get the new belt from SS. Hopefully the clamping bolt was not tight and that will correct it.

I have a 500 I bought new in 1985 and it only has the outward travel bolt.

[JPG]

IIUC The upper belt has also slipped a groove towards the quill.

A 1985 500 likely has the older water pump bearing etc, therefore only one screw holding the eccentric 'in'.

[chapmanruss]

Looking at the pictures the Idler bearing and shaft are pulling back out of the eccentric. It has been a while since I last had a headstock apart but shouldn't there be a set screw in the eccentric holding the bearing in place?

[JPG]

Looking at the pictures the Idler bearing and shaft are pulling back out of the eccentric. It has been a while since I last had a headstock apart but shouldn't there be a set screw in the eccentric holding the bearing in place?

Not on a M7.

eccentric old new.jpg (61.9 KiB) Viewed 1246 times

That 'extra' groove a stop fer the M7 pulley?
https://www.shopsmith.com/ownersite/cat ... r_note.htm

[dusty]

Take a hold on the drive hub and gently pull. See if you can pull the bearing (and shaft) out far enough for the bearing to be nearly flush with the exterior of the headstock casting. Doing this will pull the belt into better alignment.

Then check the eccentric - it must be loose or the casting is cracked.