Out of a half dozen I only really worry about one guy. A BIL married to one of my wife's sisters. Everybody else would be fine by me just mentioning that you must not try to turn the speed control without the unit running but this one is sadly pretty far gone and if I ask him to not turn them he is likely to try it as soon as my back is turned. He just has some pretty serious problems now (he was always a bit strange
I was always a little disappointed that SS didn't make better provisions to prevent the problem. They did have plans for a little piece of steel with a hole that you slipped over the dial crank handle and locked down with a padlock and I may whip out something like that for all of my units. I have long found that a lot of "unfamiliar" shop visitors have an almost uncontrollable urge to turn that speed dial whether they are 8 or 80...
I guess I could just buy a string of PowerPro's to replace these but that would take up about 70 years of shop budget.
.