Thanks for the all the input everyone.
RJSakowski: that's pretty much exactly the design I used. Yours is prettier, butbsame principle. I think if I added a second clamp, it would totally lock the table.
Markf and 4gsr: I agree - I think it's "good enough" as is. The 40:1 gearing is the reason it can overcome my single clamp. For that reason, I don't plan to change anything or add a second clamp, at least for the time being. If'n I have problems on the mill, I'll go that route.
Toolmaster and everyone else: thanks again for the suggestions! Very much appreciated, and I'll definitely draw on those if my mill is able to wiggle things a bit!
Best regards,
Lee
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