Leg Vise Construction Question: When using a parallel guide, are supporting weight bearing wheels required?

[Tim Bridge]

I'm in the process of designing the chop for my leg vise and I'm trying to determine if supporting bearing wheels are required -- or what purpose they serve.  Obviously, the keep the parallel guide perpendicular to the leg and thus keep the chop parallel to the front plane of the bench.  However, I've seen many implementations that forego the bearing wheels.

Here's two images of the designs in question:

With bearing wheels 

Without bearing wheels

I like the design of the chop going all the way down to the floor (or just above) much more than the design with the chop stopping at the bottom of the parallel guide.  I'm trying to determine if the purpose the bearing wheels serve is important enough.  

What is it about the "bearing-less" implementations that _let_ them be bearingless?

I imagine weight is a factor since, without the bearings, the weight will rest entirely on the screw.  My chop will be Douglas Fir 32" x 6-1/2" x 3".  I am using Lee Valley's Tail Vice screw, re-purposed as a leg vise screw.

I know another option is to do as Jay Bates has and how Schwarz mentions in his workbench book and use a tapered board on the floor that slides in and out, but, right now, I'd like the parallel guide.

If it matters, here is iteration two of my chop design.  By no means is it ready for construction yet, though! https://3dwarehouse.sketchup.com/model/16c8846b-6ae3-4691-9a02-e11abef6fcc9/Leg-Vise-v2-in-progress

 

Thanks for reading!

[Eric.]

The short answer is the wheels make for smoother operation.  You can forego them but if you don't create a perfect mortise for your parallel guide and it creates problems with the movement, you have no adjustments at your disposal.  You're just stuck with it.  If you want a vise that goes to the floor I'd look at the criss-cross instead of just skipping the wheels.

Your first image wouldn't load for me.

[Tim Bridge]

Eric, 

Thanks for the response.  I see.  I've also seen an implementation that uses only one bearing wheel, behind the leg, on the top of the parallel guide.  Like this image from this project.

What are your thoughts on that approach?

Another thing I've considered is mortising out a "window"/"pocket" in the chop where the outside bearing mechanism could fit when the viise is closed.  Have you ever seen anything like that before? And/or what are your thoughts on that approach?

As much as I'd love the crisscross, it's just not in the budget!

 

[Tom King]

Another option is a linear bearing rod.  I originally found these forums doing a search to see if anyone had built a bench using a linear bearing rod.  Some have not found good longevity with them, but it looks like to me that their chop was too thin, and also only using one bearing in the leg.  A 3" thick chop should help, but I'm not sure that Doug Fir would be dense enough that the hole for the rod wouldn't get weaker over time.

The last time I was looking, there was a guy in England selling benches using linear bearing rods.

[Tim Bridge]

Thanks, Tom.  I also considered the linear bearing rod but decided I wanted to go traditional for this build.

[Eric.]

6 minutes ago, Tim Bridge said:

Eric, 

Thanks for the response.  I see.  I've also seen an implementation that uses only one bearing wheel, behind the leg, on the top of the parallel guide.  Like this image from this project.

That would help when torque is being applied during clamping, but the lack of a bottom wheel still presents the possibility that the vise will not travel smoothly.  What you might do is try it without the wheels, and if it doesn't work well...just add them.  Be sure to design your bench so that it can accommodate the wheels if you decide you need them.

[Tim Bridge]

Eric,

Thanks again.  What do you think about my idea of mortising out a pocket on the back side of the chop into which the front bearing can fit when the vise is closed?

I think if I design my front bearing mechanism so that it has a (relatively) low profile, I can fit within the 3" of chop thickness I have.  This way, when closed, all one would see is the wood of the front of the chop.  Then, once it opens, the front bearing mechanism is revealed.

Tim

[Eric.]

Yeah I think that's doable.  I think you will need all 3" of that chop though,  because my chop is 10/4 and if I had to mortise out to accommodate the diameter of the wheel, I might only have 1/8" or so of meat left...which would still probably be fine, but I wouldn't like knowing it's that thin.  1/4" at least would be preferable.

[Tim Bridge]

Gotcha.  Ideally, I can fit it but, worst case scenario, I could make it a through mortise and make a "window" instead of a "pocket".

However, now I'm debating going with Jay Bates & Schwars' style of using a tapered board at the foot of the chop and saving up for the criss cross.

Thanks for the ad-vise.  I have some thinking to do.

[Eric.]

Just curious though...is the long chop purely an aesthetic thing for you, or do you think there's some advantage to be gained from the longer chop?

[Tim Bridge]

Purely aesthetic.  I'm not 100% tied to that either -- I just really like it.

[Tim Bridge]

Might anyone know where I can find a leg vise parallel guide template that I can print out and adhesive spray.  Of course I can lay it all out pretty easily but figured I'd ask if anyone knows of a template out there?

[SawDustB]

I'm using the same vise screw as you for the leg vise. The difference is I went with the criss cross. You don't need to buy the entire vise from benchcrafted - they will sell you just the criss cross, and it's less than I thought it would be. I think it's around $99 (USD) for the solo version (fine for a new bench)? Totally worth it, in my opinion. That screw will certainly work, but I think you want to have the bearing wheel if you're not going with the criss cross. The screw doesn't seem like it would travel smoothly with that much weight cantilevered off of it.

If you want, check out my build thread for pictures, etc. 

My workbench (yes, it's a Roubo)

[Tim Bridge]

Brian, 

 

I'd love to get the criss cross but even at $99, I can't justify it.  For sure, on my next bench build (a 12'-er that'll go against my North wall and be made of something other than construction lumber) I'll be getting all the best hardware but for this build, I can't justify it, heh.

I'm going to go with the the bearing wheels method and end up mortising either a pocket or window in the chop just under the parallel guide to house the front roller bearing when the chop is closed. I think that'll work.

My next design problem now is where to find a good bushing for the front of the leg.  Benchcrafted ships with an acetal plate that you fit in.  I'm thinking of using simply PVC -- sure, I'll have to change iit more often (but still very little -- I am just a hobbyist, after all) but it should prevent the lateral rocking just as well.

 

Your bench is beautiful!  Truly an inspiration!

[Tim Bridge]

In looking at the instructions from Bench Crafted as per this PDFon page 19: https://benchcrafted.com/PDF Files/BC_Glide_Leg_Vise_Instructions_Templates_Nov2012.pdf

I see that they include an acetal plate to use as a bushing at the front of the leg.

I was wondering what you guys think of using a PVC pipe of 1/2" or 1" or something like that as a bushing for my screw at the front of the leg?

Sure, I will need to replace it much more often but I wonder if it'd help much the the lateral movement of the chop?  Does anyone have any opinions?