Shopsmith Forums

I mounted a drill chuck on the upper auxiliary spindle of my ~2 year old DIY PowerPro today and was surprised that it exhibited a large amount of runout. I checked runout on another machine using a 3-3/4" lathe face plate, measured about +/- 0.001" from where I zeroed it. I measured about halfway between the outer holes and outer edge. Moved the face plate and measurement setup to the PP, where it measured +0.004" to -0.0016", or 20 thou total. Not good enough for some things, but I'm thinking okay for now on SPTs.(?) Wondering what others think. It might have been this way for a long time, even since it was put together. I've recently rearranged my shop and have no recollection of ever using this for anything other than SPTs before today. Bearings aren't making any noise, but still seem to be the most likely culprit.(?)

I had noticed about a month ago that this machine has a bit more rotational free play (between the two upper spindles) than is normal and think the Drive and Ring is likely going bad. Had previously attributed this to the infamous PP torque jitter. It's starting to make noise when spinning up some loads, like a saw blade. Now thinking there might be runout on both ends of the drive sleeve, causing high wear on the Drive and Ring.

- David

I eventually determined that the runout problem I experienced with the Drive Sleeve was caused by the shaft itself. To confirm I used this setup to measure runout at the approximate center of the bearing location of each of two shafts. (I had a disassembled 'old style' Drive Sleeve in a pile of parts and used it for comparison.)


I assembled a shaft adapter from 2 3-3/4" lathe faceplates:


This is no kind of lab setup for measuring, there is unknown runout at the PowerPro output shaft and each of the faceplates, plus how accurately they are assembled, contribute runout. But with a known good shaft for reference it is clear that the suspect shaft is bad. My baseline (old-style) shaft measured 0.009" TIR at the inner bearing location and 0.005" at the outer bearing location. The suspect shaft measured 0.053" at the inner and 0.023" at the outer.

I'm a bit disappointed in the quality but glad to have isolated the cause. Also glad I checked the shaft before installing new bearings on it. I'm reasonably certain that the runout led to premature wear on the Drive and Ring, causing the slight rotational slop I noted and the startup noise I have recently noticed when spinning up a saw blade.

- David

David,

Thanks. Interesting findings. I wonder if this problem is more pervasive, i.e. how many others are seeing this? The reason why I say this is that I seem to remember seeing several forum members comment on broken power couplers in the last year or so. I can't say how often these complaints have come up in the past. Just wondering if this might explain more members complaining about broken power couplers, particularly while using the bandsaw function lately. Enough runout (beyond any SPT<->headstock alignment issues) could cause added heat and stress to the power coupler resulting in premature failure. Just a thought...

RFGuy wrote: ↑Sun Oct 09, 2022 7:12 pm David,

Thanks. Interesting findings. I wonder if this problem is more pervasive, i.e. how many others are seeing this? The reason why I say this is that I seem to remember seeing several forum members comment on broken power couplers in the last year or so. I can't say how often these complaints have come up in the past. Just wondering if this might explain more members complaining about broken power couplers, particularly while using the bandsaw function lately. Enough runout (beyond any SPT<->headstock alignment issues) could cause added heat and stress to the power coupler resulting in premature failure. Just a thought...

That's possible. I never noticed the runout with just a hub and power coupler. But I'm reasonably certain it has always been there. The easy way to check without doing runout measurements is to put a sanding disc on and run at a low speed to observe wobble.

- David

DLB wrote: ↑Mon Oct 03, 2022 2:12 pm ... this machine has a bit more rotational free play (between the two upper spindles) than is normal and think the Drive and Ring is likely going bad. Had previously attributed this to the infamous PP torque jitter. It's starting to make noise when spinning up some loads, like a saw blade. Now thinking there might be runout on both ends of the drive sleeve, causing high wear on the Drive and Ring.

I replaced this drive sleeve, including Drive and Ring, with a used one from a conventional headstock. (Same style, with the aluminum pulley.) This greatly reduced the rotational free play and eliminated the start up noise I was getting with a saw blade. I conclude both symptoms were likely caused by premature wear of the Drive and Ring due to excessive runout.

- David

I'm happy to report that Shopsmith is replacing the subject Drive Sleeve Assembly under warranty due to the high runout shaft.

- David

DLB wrote: ↑Tue Nov 01, 2022 1:46 pm I'm happy to report that Shopsmith is replacing the subject Drive Sleeve Assembly under warranty due to the high runout shaft.

- David

David,

Excellent! Good to know. Also, when you get the replacement, can you repeat and let us know your findings on the new one? Just curious for comparison's sake.

RFGuy wrote: ↑Tue Nov 01, 2022 1:55 pm Excellent! Good to know. Also, when you get the replacement, can you repeat and let us know your findings on the new one? Just curious for comparison's sake.

The new drive sleeve, measured as similarly as possible to the previous, measured TIR of 0.004" at both bearing locations, a bit better than my old-style 'reference' shaft which measured 5 and 9 thou at the outer and inner bearing locations. The setup was slightly different because the new shaft is fully assembled. Keeping in mind that my setup was not lab quality, this is excellent.

For those measuring by eye, runout (wobble) was very visible on the bad drive sleeve with a small lathe faceplate. With a sanding disc, it was ridiculous. I never noticed it with an SPT coupler.

- David