# Linear Bearing for leg vise



## nicholasrhall

I saw an interesting post about the use of a linear bearing in lieu of the traditional pin board to prevent a leg vise from racking. It looked pretty effective, and it's cheaper and easier to install than a benchcrafted Criss-Cross. That said, I've never seen anyone else post a successful implementation. Are there any lumberjocks out there who have tried it? BTW, I think Richard McGuire sells a ready-made linear bearing kit in the UK, but this isn't in my budget. I'm talking about a linearing bearing implementation using off the shelf parts. Before any mentions it, I know it generally isn't very much trouble to adjust the pin in the traditional pin-board; I just like the idea of having automated anti-racking built into my leg-vise.

Here is the link of the linear bearing mechanism:

http://www.thewoodwhisperer.com/articles/roubo-workbench-leg-vise-alternative-linear-bearings/

Thanks in Advance and happy New Year!


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## richardwootton

I remember seeing some one give it a try on the Work Bench Smack Down thread and if I remember right it didn't go quite as well as planned, but still worked.


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## jmartel

That would be me, Richard.

Nicholas, I used the shaft and linear bearing idea on my workbench, and I cannot recommend it. While in theory it works, and it works in the above example, I couldn't get mine to work properly and now have to use spacer blocks. So, all in all, it was a waste of about $75.

I've debated getting rid of it and going to the traditional pinned board. I'm sure I can find another use for the combo.


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## nicholasrhall

That's too bad. Have you figured out why it doesn't work?


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## shipwright

Just thinking out loud but if this is supposed to work, as I assume it is, the way a holdfast works maybe it would do better with something that wasn't designed to slide. In my mind a linear bearing that is a perfect fit to the shaft would have trouble jamming. The longer it was the worse the problem would be. 
I'm not about to argue with Marc as I haven't tried this but to me it seems that something shorter, looser and rougher than a linear bearing might work better …....... or not. 
The idea is certainly intriguing.


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## nicholasrhall

I've been thinking about the use of friction in a leg vise, but I can't find anyone else who has done something like this. There is probably a reason for that 

I was thinking that it might be interesting to experiment with clutch lining material.

http://www.mcmaster.com/#clutch-lining/=q2dhat

The idea would be that the vise would slide as long as it was wasn't under torque, but that as soon as torque is applied when the vise is tightened, taking the parallel guide out of parallel, it would sieze up due to the clutch lining. The clutch lining is sold by the foot in a variety of widths. For about $10, I can buy a 1" x 48" x 3/16" precut clutch lining strip to play with.

I would glue some lining to the top & bottom of my parallel guide, and some to the top and bottom of the parallel guide mortise through my bench leg. In theory, the parallel guide would slide easily when not under torque, but would seize due to friction as soon as the guide went out of parallel. In practice, I'm guessing this would just make for a non-sliding, non-working vise that get's hopelessly seized every time it clamps. I would still love to try it of course to figure out exactly why it doesn't work


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## nicholasrhall

So far I've heard one vote saying don't do and nobody has responded saying it works. Surely there is some lumberjock who got this to work?

Anybody?


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## ekohlwey

I recently attempted this and experienced the same negative result. Finding no other discussions of this, I thought I would resurrect this thread to share my experiences in order to warn others that may be contemplating this idea. The TL;DR (for me) is to suck it up and go with some of the nice purpose-built, well designed and thought-through hardware that is commercially available for leg vises (via folks like Benchcrafted).

Technical issues aside, the costs of creating this system are quite high. I think I invested a total of around $500, between parts and labor at my local machine shop. I see no evidence that the performance can be any greater than the St. Peter's Cross systems created by Benchcrafted (for example) but the risks posed by the design challenges are much more significant.

I think that there must be some significant details missing from the build shown on TWW's site. It seems unlikely even theoretically that such a design could work, due to the very tight tolerances required of the bearing, and the extreme load that would be produced in the linear bearing.

I used a ceramic bearing that allows for approx. 2 degrees of shaft play, and tolerates very high loads compared to ball bearings (I think up to 20,000 lbs), thinking this would be a more robust configuration. The shaft racks severely in the bearing (visibly more than 2 degrees) and as a result is probably also destroying the bearing. It gets stuck against the floor and is a bugger to unbind.

Seeing this result, I am skeptical that a ball bearing with lower tolerances and load rating could possibly work.

As jmartel notes, it clearly has worked for someone, but the details of their build and reproducibility make this a bad bet for most folks.


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## wormil

Better alternative


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## Jsavalla11

I think to solve racking problem, you'd have to increase the length of the linear bearing shaft. If a tolerance of play at 1" long bearing is say 1/32' that'd suck. Increase the same bearing to 4" and the length of the vice shaft inside the linear bearing would probably be 1/128". The loads are probably not even close to what they can handle. Get the double wide flange mounts. I'm going to try it if I ever start on my roubo.


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## wormil

Yeah I don't see any reason it wouldn't work if the bearing service is long enough and attachment to the vise face is rigid.


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## unbob

I will look for a photo of my traditional leg vise I rebuilt from a 100yr old one. I find the racking action important to grab the hard to hold pieces. In this way, adjusting the pin location to effect the jaws to contact more at the top or pinch the work. If the jaws contact even a little at the bottom, the part will slip out.
The linear bearing would make for no further adjustments for jaw angle.

Here it is holding a #7 handplane for hand scraping flat, a very slippery item needing just the right amount of top pinch to hold solid, using the lower pin location to achieve the jaw angle.
Some woods that I am working are as slippery as the cast iron plane, and need that angle adjustment.

http://i170.photobucket.com/albums/u265/donsmonarch10ee/DSC01262_zps14bwmanf.jpg[/IMG][/URL[/URL]]


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## crank49

Just thinking out loud here, but I built a press a few years ago for a manufacturer of auto components and it used four heavy duty drawer slides to acheive perfect liner motion without racking.


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## cobnashine

I saw this article online, http://www.thewoodwhisperer.com/articles/roubo-workbench-leg-vise-alternative-linear-bearings/,

and decided to make an inclined leg vise using linear bearings, and it racks something terrible. Here are some pix:



























So there are 2 steel shafts, each riding in 2 linear bearings (all from McMaster-Carr), so the threaded screw doesn't have to apply any torque to the chop. Handwheel moves the chop in and out freely, but when I clamp the work piece, the bottom of the chop moves toward the bench a half inch more than the top. So the chop is skewed, that is, it leans in at the bottom, and makes it difficult to secure the workpiece.

Any suggestions? I think the wood of the chop is not sufficiently hard or strong to prevent the steel shafts from tilting as the hand wheel tightens the jaws of the vice onto the work piece. I placed a square on each shaft, and before tightening, all was perpendicular, but the more force the chop applies to the workpiece, the more "daylight" can be seen between the blade of the square and the inner surface of the chop.

At worst, I'll rebuild the thing and use the criss-cross from Benchcrafted.


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## crank49

Why not build these with two screws tied together by a chain drive?
No racking then, and perfectly parallel movement.
You could put the sprockets on the back end of the screw shafts so they would be under the bench and out of sight.


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## Lazyman

I just looked at the video for the criss-cross from Benchcrafted. If the video is accurate, at $99-$139 I am not sure why you would use anything else, especially if the linear bearing approach is going to cost you $75 anyway.


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## shampeon

I've got the criss-cross, and it's great. Boatman5 here sells a chain drive that's really slick. No need for a separate additional screw.
http://ancorayachtservice.com/?page_id=196


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## AndreyKharitonkin

cobnashine, I found it very helpful to build prototype first, but it is probably late to suggest.

I think you didn't add inclination angle where rod goes into the chop. Depending on material of the chop and thickness and how strongly it is joined with rod, different inclination angle is required. It will determine how much pressure to work piece will be applied at the moment when it becomes parallel with the leg and before it goes out of parallel again. Basically, when hole in the chop is drilled, it has to be done with 1-2° angle skewed, so that the top of the chop touches bench first. As others suggested, you can always add chain if it doesn't work (search for Chain Leg Vise), it works really well with linear bearings.

Linear bearings are different from other ways of preventing racking is that you are limited in how much pressure you can apply by materials and construction. In other known ways, e.g. pin, criss-cross, chain, it depends on how strong you tight the screw, more or less. Benefit of linear bearings for me is that it's easy in my small space to remove leg vise and use holdfasts with something very long and wide like a door and relatively cheaper/simpler to make.

I like your construction with two rods. Potentially, it can be the best of two worlds - smooth to operate as criss-cross and angled leg for better grip on long vertical pieces. My leg vise will be also with offset from vertical like angled leg vise but with single rod and vertical chop. So far I built working prototype from pine/spruce.

Interestingly, some instructions on assembly of other vises are helpful for installation of linear bearings leg vise too. For example, while installing twin screw end vise I learned that oversized hole in chop for screw is indeed required to compensate for any misalignment. In instructions for criss-cross installation there is acetal bushing that allows that. Same with linear bearings - install bearings first with tested angle between rod and chop and then tune position of the screw by securing screw in the chop last, through oversized hole in it.


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## kiefer

Here is a vise that I developed and eliminates the lower pin bar and also has a auto quick release system which allow you to rapidly change the opening of the vise .
This leg vise is all shop made with very little expense .
I attach a link to one of several videos that shows the vise in action and I also posted a video on the quick release that is of my own design 








http://lumberjocks.com/projects/229242

Klaus


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## Mylez

I bought the parts, 30 mm bearing, rod, Yost Screw, etc to do the build I saw on https://aroundhomediy.com/build-roubo-workbench-leg-vise/. If I had read this thread first I might have gone a different route but since I already have all the parts, I'm gonna give it a go. I have to build the bench first. All the lumber is milled, I just need to start putting it together.


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## AndreyKharitonkin

> I bought the parts, 30 mm bearing, rod, Yost Screw, etc to do the build I saw on https://aroundhomediy.com/build-roubo-workbench-leg-vise/. If I had read this thread first I might have gone a different route but since I already have all the parts, I m gonna give it a go. I have to build the bench first. All the lumber is milled, I just need to start putting it together.
> 
> - Mylez


It works alright with 30 mm bearing, just don't forget to drill holes in chop at an angle of 1 degree or slightly more. Like 1/50 ratio or 1/2" gain in 25" length. And do not epoxy rod but let it go through the chop and then fixed with shaft supports bracket on the outer side with screws. This point needs all the strength it can get.

If you can make a prototype to see how wood of your choice and other materials flex at desired clamping pressure.

You can always adjust this angle, if you can remove the rod and the screw from the chop (do not epoxy rod). Just plane inside side to give it more taper towards the bottom.

Drill oversized hole in the chop for the screw - similar as with other leg vise installations - it will allow to align it better for smooth operation.


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## Mylez

Playing around with the layout of my jaw. I can't wait to see how it comes out. I'll glue up more maple around the pauduk and bevel and taper until it looks cool. That's my plan anyways.


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## Foghorn

Leg vises look real cool but the more I see them and the associated issues, I'm glad I've never gone that way. Just my humble opinion of course having never used one.


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## HokieKen

I absolutely love my leg vise and use it way more than I thought I would when I built my bench. I used a traditional pin-type parallel guide and it works flawlessly. About a year ago, I retrofitted it with a Hovarter mechanism in place of the screw which made me kinda lazy so I asked for (and got) the Hovarter x-link for Christmas this year. When I have time, I'll be ditching the parallel guide and installing the x-link.

Linear bearings aren't practical for this application IMO. To prevent racking in a situation like this, you need a rod and bearing of high precision and fit and you need it installed pretty dang close to dead parallel to the force line of action of your screw. You also need the screw to have no slop in it. It may be effective enough to minimize the racking to the point where it's acceptable for use though. So no harm in trying it out!


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## Mylez

Slowly but surely coming together.


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