Shopsmith Forums

Good day, I'm relatively new to Shopsmith. I got a Mark V Model 500 from my great uncle and I've been slowly working at getting everything working well. The one thing that has stumped me is I can't seem to get the speed adjustment dialed in. I have a laser tachometer and I can set the high rpm on the dial to 5200 rpm, but then when I try to set the set screw for the high speed stop it's like the screw isn't long enough. If I turn it in til it contacts the quadrant there aren't any threads left for the jam nut. Can anyone point me in the right direction what to check next?

I'm starting to suspect someone put the wrong drive belt on. If I adjust the speed dial to show "fast" at 5200 rpm, the slowest I can get it to go is 750-ish which is around C on the dial. If I adjust the dial to show "slow" at that slowest achievable speed of 750 rpm, it's hitting close to 6700 rpm at the top of the dial. I'm thinking maybe I should replace the belt with a SS belt and see if the high speed stop is within range of the quadrant.

What you are experiencing is normal or at least consistent with my experience.

I set the high speed stop to maintain some clearance between the spinning floating sheave and the stationary part of the speed change mechanism so that they won't be in contact. I prefer as fast as practical, but generally the only time I run it this fast is for maintenance, either lubrication or to remove the lower belt. But as a check, the outside of the belt should not extend beyond the outside of the motor sheaves.

I set the speed dial to be 'correct' at a much lower speed where I'm likely to be actually using the headstock and where it gives me greater accuracy.

It is certainly possible that you have an incorrect belt, but it could also just be a different belt preferred by others.

There is way more information than you want in this thread: (viewtopic.php?t=29903&start=110). But there was also some incorrect information or assumptions near the beginning. It's not an easy read. But you can see what at least several other members measured on their machines. I picked a start point kind of in the middle, a page with a graph of the speeds I measured sat one point.

- David

i.e. Ignore the tach, and set it to restrict the mechanical limit.

OR just adjust the screw so the end is flush with the locking nut(assuming the thick nut - else about 1/8" proud).

Most belts nowdays are narrower than the 1950's version. This shifts the speed range upward. Belt wear has the same effect.

Belt length has a similar effect. Again finding belt length today to the original length is evasive.

BTW I think the "700 to 5200" range is an approximation to begin with. Note no numbers on the dial.

Stop sweating the small stuff.