Leg vise question

[Mike Henderson]

Fine Woodworking (FWW) has an article in their latest issue of "Tools & Shops" about building a Roubo bench, with a leg vise.

For those of you who have a leg vise, I have a question. It seems that a leg vise has two center points of support - the screw and the parallel guide. Because of that, it seems that the vise would have serious racking problems if you put something in the vise off center. Is that correct? Must the work be centered in the vise for the vise to work well?

The advantage I see for a leg vise is the deeper space between the top of the bench and the screw. But it has the disadvantage of requiring adjustment of the parallel guide when changing the size of the piece clamped.

So what say you? How do you like a leg vise? If you've used other vises, how does a leg vise compare to other types of vises, including a European type vise which allows you to clamp something all the way down to the floor?

Mike

[george wilson]

You can make a sort of stepped pyramid to insert on the opposite side of the vise where your piece is clamped. Select the step to match the thickness of your workpiece. There are several ways to eliminate racking.

[Chris Griggs]

I have a slanted leg vise that I quite like. They are really nice if you prepare stock by hand and do a lot of edge jointing because the depth lets you put the board on edge nice and deep/low in the vise.

Because mine is slanted I can't quite do and apples to apple recommendation though. The slant allows me to clamp a board vertical in the vise so that it is centered over the fulcrum of the screw at the top where the clamping pressure is but hangs to the right side of the screw at the bottom of the board.

Still sometimes I clamp things where the board isn't centered at the top. There is some racking but its really only bad if you clamp way off the center of the screw. I would imagine that on a straight leg vise as long as you clamp the piece right next to the screw you won't have a major racking problem.

[Andrae Covington]

...It seems that a leg vise has two center points of support - the screw and the parallel guide. Because of that, it seems that the vise would have serious racking problems if you put something in the vise off center. Is that correct? Must the work be centered in the vise for the vise to work well?...

Sometimes racking is an advantage. For example, holding a tapered table leg.

244189

In my experience, the racking caused by placing work off-center is more than compensated for by the tremendous grip. I can't even begin to pull this piece of wood out of the vise. I was able to rotate it out with a few hits of a deadblow mallet. So holding the workpiece off-center and trying to mortise probably wouldn't work out well. But I don't use the vise for mortising in the first place.

244190

Despite the stunts illustrated above, I do normally try to approximately center the work in the vise, or hold it with both leg vises.

[David Posey]

Still sometimes I clamp things where the board isn't centered at the top. There is some racking but its really only bad if you clamp way off the center of the screw.


This is pretty much my experience with a vertical leg vise. There is only so much play in the screw, so it can only rack so far before it has to start biting. I still try and clamp in the center, but i I have to clamp near the edge for some reason I just put a piece of stock that's the same thickness in the other side.

Also, lining it with leather increases the amount of grip tremendously.

[Jim Ritter]

Hi Mike I just sent you a PM. I am a big leg vise fan and there are solutions to the pin issue, one I've been working on for a while. As to the wracking it really isn't that big a deal mostly because you can clamp close to the screw due to the fact that there are no guide bars on either side of the screw. They would naturally force you to clamp further away from the screw. Derek Cohen posted a while back ( not even a month ago) about how he dealt with his battle with wracking. But as a previous post has stated, it can be your friend.

[Jim Ritter]

Here is the link to Derek's post, one of them anyway. http://www.sawmillcreek.org/showthread.php?189000-Leg-vise-Parallel-Guide-Adjuster-by-Ancora-Yacht-Service it was on page three.

[Ron Brese]

Been using mine for two years and I have no racking problems. The size of the screw helps a lot to resist any twisting. They've also just introduced the "Criss Cross" which eliminates issues with moving the pin in the parallel guide. It's a very elegant solution to the parallel guide. I plan to retrofit my bench with the "Criss Cross" in the near future.

Ron

[Mike Henderson]

Been using mine for two years and I have no racking problems. The size of the screw helps a lot to resist any twisting. They've also just introduced the "Criss Cross" which eliminates issues with moving the pin in the parallel guide. It's a very elegant solution to the parallel guide. I plan to retrofit my bench with the "Criss Cross" in the near future.

Ron
So we have two options for automatic adjustment of a leg vise - the Criss Cross and the Chain Leg. Anybody looked into them and have any comments, recommendations, etc?

Mike

[Bill Houghton]

Fine Woodworking (FWW) has an article in their latest issue of "Tools & Shops" about building a Roubo bench, with a leg vise.

For those of you who have a leg vise, I have a question. It seems that a leg vise has two center points of support - the screw and the parallel guide. Because of that, it seems that the vise would have serious racking problems if you put something in the vise off center.
You would think so, but that wasn't my experience. Not sure why; it just wasn't.

[Jessica Pierce-LaRose]

MY leg vise doesn't have too much racking in it- I feel like part of that is because of the large screw (Lake Erie wooden screw) and large parallel guide with a fairly close fit in the side-to-side dimension. This is just speculation on my part though.

Honestly, the thing with the leg vise for me, though, is that most of the jobs I use a leg vise for, the racking isn't really an issue. The things I can think of offhand where racking would present problems are mostly things that I'm apt to use another work holding method for. The couple of times movement and vibration has become more of an issue was with wider stock that hangs out of the side of the vise, when it's got a bit of bow so it doesn't pull flush to the edge of the table, but that's quickly overcome by holding the other side with the sliding deadman and a clamp or holdfast.

[Curt Putnam]

So we have two options for automatic adjustment of a leg vise - the Criss Cross and the Chain Leg. Anybody looked into them and have any comments, recommendations, etc?

Mike

I just bought a Lake Erie screw and Jim's Chain Leg adjuster. FWIW.

[Mike Henderson]

I just bought a Lake Erie screw and Jim's Chain Leg adjuster. FWIW.
The thing I like about the chain adjuster is that it's easy to install, especially on an existing leg vise. The Criss Cross looks like it'd take a lot more to install it. Also, we only have a price on the chain adjuster so it's not possible to really compare the two.

For anyone who's installed the chain adjuster, how does it work for you. Is it smooth in operation? Does it adjust so that the jaw is square to the work? Etc???

Mike

[Jim Ritter]

Here is a review that Derek Cohen did on his website http://www.inthewoodshop.com/ToolReviews/AYSLegViseChainAdjuster.html
He has a lot of very good info on his site so be sure to look at the whole site.
I think it's the best of both the old and no more adjusting. Not many people have these yet there is I guy on Lumberjocks I sent a preproduction kit to, he has installer it on his bench. His review is a couple of weeks away. If you search chain leg vise over there you might find it. He goes by ScottyB.

[Bill Houghton]

Thinking about this question some more, I realized that the lack of racking may have been because, on my vise, it was possible to clamp vertical pieces right up against the screw, because the strut at the bottom was narrower than the screw.

[Jim Matthews]

I don't often clamp pieces shorter than the chop of my vise.

If I did, I would just use the spacer recommended above, as with my Moxxon (where racking is an issue).
I like the idea of the chain adjuster, but a little slop on the lower guide makes things a breeze to adjust.

I'm likely to install two rollers - one above the upper guide behind the works, and one lower guide below the works out front.

[Jim Ritter]

Hi Jim what do you mean by "a little slop on the lower guide makes things a breeze to adjust"? What are you adjusting? I'm just curious. If it is the pin, the chain eliminates it.

[Derek Cohen]

Not meaning to distract from Jim's question, I have posted my "fix" (Parallel Guide Guide) for racking on my website.

http://www.inthewoodshop.com/ShopMadeTools/ParallelGuideGuide.html

Let me emphasise a point I made in the article - racking is a double-edged sword. It can be highly desirable, such as when clamping out-of-square pieces. The racking may be overcome by extra clamping force. In my case it was more important to avoid any boards slipping in the chop when edge jointing. The Guide Guide can be disengaged in a few seconds, returning the leg vise back to original state (although there are much better ways of adding this feature).

Regards from Perth

Derek

[Jim Matthews]

Hi Jim what do you mean by "a little slop on the lower guide makes things a breeze to adjust"? What are you adjusting? I'm just curious. If it is the pin, the chain eliminates it.

My shop is an extremely damp space - the lower guide swelled this Summer to the point that I was forced to disassemble the works and shave off a little from
the upper and lower ends, where I have HDPE glide surfaces attached. Laterally, there's little play and it seems stable - but I like Derek's solution to keep things straight.

If we look at the vise in three dimensions (X left-right Y in-out and Z up-down) I have little play in X and plenty in both Y and Z.
This play in Z made the adjustments much easier - as the works only engage the HDPE at the end when the chop it tightened.

I intend to replace it with a pair of rollers, spring loaded to account for seasonal movement of the lower guide.

This will wait until after Sandy passes - it's so humid today that I can hardly get the drawers to open in my bench.

[Trevor Walsh]

The criss-cross is just plain easier. It's a simpler mechanism and doesn't have all the through mortises and extra components. I'm looking at getting a pair to put on a massive ash bench with wooden screws I'm making. The chain adjuster seems better than the regular parallel guide, but I think both are inferior to the criss cross mechanism.

[Mike Henderson]

The criss-cross is just plain easier. It's a simpler mechanism and doesn't have all the through mortises and extra components. I'm looking at getting a pair to put on a massive ash bench with wooden screws I'm making. The chain adjuster seems better than the regular parallel guide, but I think both are inferior to the criss cross mechanism.
Is that Criss Cross available yet? I couldn't find it on their site. Is there info on it somewhere, especially on how it works? I saw somewhere that it was patented long ago (maybe the 1920's) so I guess I could do a patent search.

Mike

[Jim Ritter]

It is an old patent and in fact so is the chain. The chain patent will be 165 years old this February. The St Peters cross is very simple. The two upper arms are pinned to the leg and the chop. As the screw moves in and out the upper arms move and so moves the cross. As a piece of wood is clamped the lower part of the chop wants to move in, but if the upper arms are not moving the lower arms are not moving. It might seem easier to install but if the two holes for the pins are not dead on, and the long trenches are not identical, the jaws will not be parallel. I do not know what provisions have been made for adjusting. The chain really only requires a 5/8" hole bored through the chop and leg, with a 1" counterbore in the chop to seat the end button. Everything else can be surface mounted. There is a screw on the back end of the chain for adjusting to parallelism, or out if you really need to clamp a tapered piece.

[Mike Henderson]

The criss-cross is just plain easier. It's a simpler mechanism and doesn't have all the through mortises and extra components. I'm looking at getting a pair to put on a massive ash bench with wooden screws I'm making. The chain adjuster seems better than the regular parallel guide, but I think both are inferior to the criss cross mechanism.
I've been doing some reading and thinking about the two approaches. Searching the web, people who have implemented a criss cross approach are reporting problems with the mechanism. Now, it's possible that they just are doing an inferior approach but I can understand why they might have some problems, just from the inherent design of the criss cross mechanism. Both approaches require that the mechanism be attached very close to the screw so that the bottom moves in parallel with the top of the chop.

For the criss cross approach, the bottom pivot point for the chop moves upward as the criss cross is opened (the vise is opened). So the arms of the criss cross have to be long (the criss cross needs to extend all the way down to the bottom of the chop when closed) and yet very stiff to avoid flexing - since the screw is between the work and the bottom pivot, the force on the bottom pivot (the bottom of the criss cross) will be close to the force on the work - so the cross has to stand up to a lot of force without flexing. Additionally, the bottoms of the arms may need to ride in a track to keep them aligned as they move up and down. If the criss cross is not directly below the screw, and centered on the chop, the chop will rack when it's closed. The requirements for stiff and long, plus any other requirements (such as riding in a track) could mean that the criss cross will be expensive.

The criss cross mechanism needs to be buried into the leg or chop so that the vise can be closed completely but that's just an installation problem.

The chain approach seems to maintain the existing design of the leg vise, only providing an automatic way of keeping the chop parallel. In other words, it simply eliminates the need to reach down and stick the pin in a different hole. Also, the chain is always in tension, which is easier to deal with than the force the criss cross has to withstand.

You were very definite that you felt the criss cross approach was superior and I'm wondering why you feel that way.

It seems that both approaches will work. The choice, in my opinion, would be determined by the expense, the smoothness and accuracy of use, and the ease of installation.

Mike

[Thinking about the chain approach a bit more, it seems that it's important that the bottom of the chop moves inward as you close the vise. That is, imagine you had cranked the vise out all the way and are now closing it to clamp a small piece of wood. Since the chain is not solid, it must be pulled back into the bench, and the only way that can happen is if the bottom moves inward as you're closing the vise. I wonder if some tensioning mechanism would be required to make sure the chain doesn't get fouled between the leg and the chop when closing the vise.]

[Jim Ritter]

Thanks Mike, good job describing the cross. But another issue is the pin location and alignment. If that is off it will not run true.
I have not found a need to put any type of return pressure on the chain when tightening, it naturally goes in just as if it was the pin arraignment. The chain is always in an equilibrium until tension is applied. Since the closing of the screw moves the chop the upper part of the chain moves in with the screw there is no real resistance on the beam moving in also. As far as installation of the chain, it requires a 5/8" hole in the front of the bench with a 1" counte bore. You can even use the beam with holes if you want. Everything else can be surface mounted if you choose. That is what Derek did. Hope that makes sense I'm working off the phone, our power went out early this afternoon, other than that all good so far.

[Trevor Walsh]

The projected cost of the basic criss-cross is $99 (to be set in morti in the legs with pins, not additional plates that one is $139).

Mike, My view on ease of installation/betterness was based on part count and points of movement. I made big assumptions about one being able to excavate parallel, centered pockets with holes perpendicular and in the right places. If Benchcrafted installed it and is willing to sell it, it's doable. Retrofitting their vises or installing a tail vise is probably more difficult. I'm also approaching this from the viewpoint of building a bench from scratch/installing a new vise, thus there wouldn't be a big through mortise for the parallel guide, instal of that in the chop making sure that works and adding the chain mechanism.

I do think if you had a parallel guide already, the chain mechanism would be a faster add on. I should have stated my assumptions in the beginning.