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Sagging leg vise?

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Forum topic by Brett posted 08-28-2012 06:27 PM 819 views 0 times favorited 10 replies Add to Favorites Watch
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Brett

621 posts in 1337 days


08-28-2012 06:27 PM

If you have built a leg vise like the one on Chris Schwarz’s Roubo bench, have you experienced any problems with the vise sagging due to its own weight?

-- More tools, fewer machines.


10 replies so far

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jmos

681 posts in 1023 days


#1 posted 08-29-2012 03:32 PM

Yes, I have a leg vise. I suppose it does sag a bit, but I’ve never really paid attention. How tight the screw and the bottom guide are will control the sag. Although, if it drops slightly I don’t see how it would effect operation. Or, to put it another way, I never had any problems with mine.

What specifically are you concerned about?

-- John

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Brett

621 posts in 1337 days


#2 posted 08-29-2012 07:09 PM

jmos, I’m just concerned that the weight of the vise might cause the screw to turn less easily or get jammed when the chop is backed out to clamp a wider piece of wood.

-- More tools, fewer machines.

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jmos

681 posts in 1023 days


#3 posted 08-29-2012 07:46 PM

I don’t think you’ll have any problem with that. I used the same screw you’re using, but I used two for my end vise (home made twinscrew vise, I used a Lake Erie wooden screw for the leg vise). They are pretty solid and turn freely. I really don’t see the weight of the chop making it hard to work.

I would plan on mortising the rear nut into your leg for additional support. You could just flip it and use the 4 screws to secure it to the back of the leg, but I would be concerned about them working loose after a while, as that is what will be holding the weight of the chop. Once it is mortised in I don’t think you will have any troubles.

-- John

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Brett

621 posts in 1337 days


#4 posted 08-30-2012 02:18 PM

Are you recommending that the entire rear nut be mortised into the leg (so the cylindrical part is inside the leg, facing the vise), or that just the square part of the rear nut be mortised into the leg (with the cylindrical part part facing the rear of the bench?

Also, if the whole of the nut is mortise into the leg, wouldn’t that leave too little wood for the screws to bite into?

-- More tools, fewer machines.

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Brett

621 posts in 1337 days


#5 posted 08-30-2012 03:37 PM

John, after thinking about it for a while, I believe I understand what you’re talking about. The screws will experience a “shearing force” (one that pushed them sideways), and mortising the square base (only) into the leg will provide some support for the nut so the screws are not bearing all the weight.

-- More tools, fewer machines.

View Smitty_Cabinetshop's profile

Smitty_Cabinetshop

9907 posts in 1272 days


#6 posted 08-30-2012 03:49 PM

Brett – I have such a leg vise and yeah, when I draw it out for deep clamping (6” or more from the edge of the bench), it does jam up a bit from sag in that the chop doesn’t stay parallel to the leg at wider distances. But lift the chop while drawing it out, set the peg at the bottom, and it’s good to go. Nothing that concerns me, really.

-- Don't anthropomorphize your handplanes. They hate it when you do that. -- OldTools Archive

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Brandon

4138 posts in 1605 days


#7 posted 08-30-2012 03:51 PM

I haven’t had this problem—- I mean, it probably sags a little, but I don’t notice it. If you’re concerned about it, you can put a skateboard wheel at the bottom of the vise and let it use the ground for support. Or spend money on the Benchcrafted roller system.

-- "hold fast to that which is good"

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Brett

621 posts in 1337 days


#8 posted 08-30-2012 04:08 PM

I like the skateboard wheel idea. :)

-- More tools, fewer machines.

View Smitty_Cabinetshop's profile

Smitty_Cabinetshop

9907 posts in 1272 days


#9 posted 08-30-2012 04:09 PM

I always have shavings on the floor… it’ll never work… :-)

-- Don't anthropomorphize your handplanes. They hate it when you do that. -- OldTools Archive

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jmos

681 posts in 1023 days


#10 posted 08-30-2012 04:51 PM

Brett, I just talking about the cylindrical portion, that way you can get the flange flush to the leg. The mortise will support the nut, and keep it from possibly moving around, and all the screws have to do is keep the nut in the mortise. Otherwise the screws have to keep the nut from twisting in reaction to the weight of the chop, which, over time, I think would cause the screws to loosen.

More info in my bench build blog, as well as a video link http://lumberjocks.com/jmos/blog/28304

Edit – Thinking about it a bit more, if you go with the skateboard wheel, you might be able to skip the mortise as the weight of the chop won’t be hanging on the nut.

-- John

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