bench leg size for leg vise

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Forum topic by dpjeansonne posted 04-18-2013 09:37 PM 2263 views 0 times favorited 2 replies Add to Favorites Watch
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72 posts in 3240 days

04-18-2013 09:37 PM

Topic tags/keywords: workbench vises leg vise

I am building a version of the 21st century workbench with a leg vise instead of the twin screw front vise.
The plans show a 3.5” square leg for the supports. My question is for a leg vise that will be 6 or 8” wide jaws, what does the leg width need to be? I have seen 5 inches on the Roubo designs but will the 3.5” work or create other problems?

-- Cajun Don, Louisiana

2 replies so far

View Mark Kornell's profile

Mark Kornell

1169 posts in 2557 days

#1 posted 04-18-2013 10:50 PM

The minimum width for the leg depends on the type of hardware you’re using for the vise screw, and to some extent, the type of wood you’re using for the leg.

First, metal screw or wood screw? A wood screw for a leg vise is typically 2 1/2” diameter, and putting that into 3 1/2” makes the leg pretty weak around the screw. You’d end up with a 1/2” wall on both sides at the thinnest point. Since the force of the screw is focused in the area around the hole in the leg, that’s a bench failure waiting to happen.

A metal screw is about half the diameter, giving you over an inch on the thinnest part of each wall. I’d have no concerns with that when using a strong hardwood.

But, since you mentioned 3.5”, I’m going to guess that you’re thinking construction lumber – 4×4 post or laminated 2×4s? If you’re going to use a softwood, I’d suggest a 6×6 instead. That gives you a considerably thicker and deeper wall.

-- Mark Kornell, Kornell Wood Design

View Willeh's profile


228 posts in 2366 days

#2 posted 04-18-2013 11:24 PM

If you are looking to do a leg vice, and want to use it to hold wide boards vertically, you’ll want to make sure that it has a mating surface behind the chop.. so, you’ll want a few inches on the side after the screw, so, that 5” wide leg may be a good idea?

-- Will, Ontario Canada. "I can do fast, cheap and good, but you can only pick two... "

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