Shopsmith Forums

As a retired accountant I have taken up woodworking as a hobby on a Mark VII in good condition. Recently at 3,000 rpm it automatically began to accelerate on its own. After reading several posts on this site, I removed and cleaned the backside of the Control knob. After reinstalling the control knob the speed is very fast no where near the 700 rpm as indicated by the control knob. The problem seems to be on the intermediate shaft. Earlier I oiled this shaft and there is a small bar on the inside of the oil hole, after my control knob fix the shaft is missing from the inside of the oil hole. As Red Green says "if it ain't broken you are not trying". Any help is humbly appreciated. Thanks.

To clarify:
* Are you saying that the control knob (23 on the parts diagram) is remaining stationary while the machine is speeding up, or that the knob is rotating on its own?
* By "intermediate shaft" do you mean the speed-control shaft (18) linking the knob with the control cam?

The knob has a double d bore. Is it possible the knob is 180° out(reversed)?

I do not understand oil hole/bar.

Speculating: If the roll pin is missing from the control-cam hub, it might look like an oil hole.

Gentlemen and Ladies if any, I had the control knob turned 180 degrees off (my bad) so now the control knob works fine. However the control knob begins advancing by itself at about 3000 rpm. Thanks for your help and time.

At higher speeds there's more push from the sheave to drift the control higher; this can happen on the Mark Vs as well. What keeps the control in place on the VII are the two spring-loaded 'bullets' on the control bracket. You'll want to make sure those aren't gunked up and their springs are good.

The pressure that keeps them working is maintained by the retaining ring on the tip of the control shaft. If it's not pulling the knob down tight, you'll want to look at the control shaft and the knob for how you're getting the slack. Are the teeth in the knob worn down?

Not saying this is likely to be your problem, but: I've just replaced a control cam, and found that on the three shafts I have, all have two drillings for the roll pin that holds the cam on. I speculate that this is to allow for variance in tension on the knob. On my main machine I tried out both holes to see the difference, and the outer one reduced control tension enough to let the knob drift across the speeds.

Somewhere I read to put a thin washer on the stud that holds the control knob so it would put more pressure on the 2 spring-loaded bullets. This seems to be working. Thanks to everyone who took the time to help me. Much appreciated!!!

StevenAyres wrote: ↑Wed Dec 23, 2020 4:11 pm . . .
Not saying this is likely to be your problem, but: I've just replaced a control cam, and found that on the three shafts I have, all have two drillings for the roll pin that holds the cam on. I speculate that this is to allow for variance in tension on the knob. On my main machine I tried out both holes to see the difference, and the outer one reduced control tension enough to let the knob drift across the speeds.

Interesting! I assume the two holes are aligned 'radially'. i.e. in line along the shaft?

JPG wrote: ↑Sat Dec 26, 2020 11:52 am Interesting! I assume the two holes are aligned 'radially'. i.e. in line along the shaft?

They're almost in line, which is additionally interesting, about as close together as they can get.

I am gonna guess the second hole was added by a po, not by SS.