Are there any tricks or gotchas to inspecting or removing the spring inside the variable speed control handle on these mills. It looks like it uses the same spring and hub as the 5900 lathes in case anyone has experience with those. Judging from the force it imparts when the speed control handle returns, I'm guessing that it needs a little care when working on it and I have no desire to repeat an unfortunate experience I once had with a garage door spring.
When I first got my Clausing 5904 one of the problems was the speed control, the hook end of spring had broken. The replacement I bought on Ebay had the spring in the inner housing, I think that's how Clausing provides them also. As long as the spring stays in there you won't have too much trouble. I seem to remember I put maybe a turn or less preload in when I put the whole thing back together. Like any spring under tension you want to be careful, but as I remember there isn't alot of preload when the control is at the end of it's travel. I don't recall for sure, so don't quote me, but I seem to recall that the spring is under the most tension when at the low speed end and provides force to overcome the spring in the variable pulley when going to high speed. Sorry I can't be more definite, but the fact this repair isn't one of the more memorable ones suggests it was no big deal, unlike the spring on the variable pulley on the motor of the mill I recently acquired!
Thanks Paul. It looks like the cap screw at the center of the speed control hub just needed to be tightened. Apparently that puts enough friction on the hub to keep it from rotating on its own. That little tip turned up from a Google Groups search.