Screw Holes for Moxon Vise: Snug or Sloppy?

[Steve H Graham]

I'm making a Moxon-style vise for my bench, using 3/4-6 acme screws.

Everything is pretty much done, except for the outer jaw. I have to drill holes in it for the screws.

Here's what I'm wondering: do I want the jaw to fit fairly snugly on the screws so it won't wobble around, or should I make the holes fairly loose so nothing will bind? I figure I can use a 3/4" Forstner bit for a tighter hole and a 3/4" spade bit for a loose one.

[Steve H Graham]

I read up on these things, and I learned that the holes have to be loose in the horizontal direction but not the vertical direction. I loaded the jaw on the milling machine, because I figured there was some tiny hope I would succeed if I used machine tools, and I made two 3/4" holes with a 2-flute cobalt end mill. Then I moved the end mill 0.050" in each direction, giving holes that were 0.950" wide and 0.750" high.

Looks like it will work. I still have to add a few refinements.

The screws can extend so I can hold stuff about 10" wide.

Hope this turns out to be useful. I've never used one.

My DVD on workshop neatness will be finished soon. I'm sure everyone will want to buy a copy.

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