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Veritas Twin Screw Vise - limit to jaw length?

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Forum topic by Fellrunner posted 03-30-2011 08:11 AM 1920 views 0 times favorited 6 replies Add to Favorites Watch
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Fellrunner

3 posts in 1623 days


03-30-2011 08:11 AM

Topic tags/keywords: veritas twin screw vise jaw length vise jaw size vise installation

The instructions for my Veritas Twin Screw Vise say that the jaw can be any length you desire. I’d like to make its jaw extend 12 inches past both screws. I have the 24 inch model, so the total jaw length would be four feet.

Any comments would be very welcome, particularly about whether there is a practical limit to the vise’s ability to handle side leverage.

Also, I’m planning on making the jaw 3 inches thick and seven inches tall—is the weight of that much wood (hard maple) going to be a problem?

This bench is my first woodworking project.


6 replies so far

View drewnahant's profile

drewnahant

222 posts in 1785 days


#1 posted 03-30-2011 08:38 AM

I dont have any experience with the veritas vises, but it doesnt seem like it should be an issue.

But when you say “first woodworking project” just how new are you, because I wouldnt recommend taking on a workbench like this right off the bat.
- A workbench has to be strong, so learn some joinery, and should really be a project to be proud of, so develope some skills first.
-Using your tools with a less than perfect bench will tell you what you really need or want for features, and vise setups, the experience will definitely develope your design.
- different benches are useful for different types of projects, so until you play with differnet projects, and decide if you like using power tools, or hand tools, small projects or furniture, and lots of other criteria, dont lock yourself into one design

I would suggest that if you have the hardware, or a good idea of what you want to use, such as the veritas vise, build a cheap temporary bench, use it, play with it, modify it. And when you are sure of what kind of projects you want to specialize in, what tools you like using, what height you like working at, and how much space you really have with other important tools in the shop, then build a real bench.

Interresting philosophy:

Traditionally a carpenter must start as an apprentice, and would slowly build a collection of tools carried in a simple box. When he was ready, he would leave his master and travel, carrying his tools in a box which he made with his finest jointery to represent his work. After years as a journeyman, he would finally be able to call himeself a carpenter, and start a shop, at which point he would build his first bench ( a rough bench with an unfinished top), and that bench would be a representation of his quality, showing his ability to cut fine joints, assemble a strong, flat top, even hand-cut the wood screws for the vises, and much more. A workbench was his pride, and his resume. He would later become a master, and at this point he would build a second bench with a finished top, and a real thought of appearance.

I’m not saying that in a modern workshop the bench should carry the same importance, but there is a reason that woodworkers have traditionally waited until they were experienced to build a bench. You can get by without it, and you will build a much better one when you have a strong foundation of skills.

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Fellrunner

3 posts in 1623 days


#2 posted 03-30-2011 11:05 AM

Thanks very much for the time you took for your thoughtful reply.

I respect your advice about first making a temporary bench so much that I did just that a couple of years ago. I’ve used that bench enough to have a good idea of what makes a project enjoyable or frustrating for me. I’m making the new bench because I so often find myself fervently wishing that my bench could hold something for me in this or that way. I should have said that this is my first fine woodworking project.

I also asked my questions to a Lee Valley customer service rep. She didn’t know of anybody who has tried such an extended jaw and was uncomfortable with more than six inches of extension past the screw. The only stress I can think of would be a bending force on the jaw’s wood at the point where the screw attaches to the jaw if a narrow piece is strongly gripped at the very end of the jaw. I’ve found a demonstration video from a bench manufacturer showing a Veritas twin screw with a jaw that extends 8 inches.

She felt that 3 inches of thickness would make the jaw heavy enough to exacerbate the vise’s tendency to lean down (there can’t be a guide bar with this design) when it’s extended half way or more. She thought that my plan to install a wear strip made of ultra high density plastic would help, but she kept coming back to how much a 4-foot x 7-inch x 3-inch maple jaw would weigh.

All of Lee Valley’s demo and in-house benches use a 2-inch thick jaw. On the other hand, one of the featured benches in Lou Schleining’s The Workbench uses a 3-inch thick jaw.

She didn’t quote any specifications. According to The Wood Database (http://www.wood-database.com/lumber-identification/hardwoods/hard-maple), dried hard maple averages 46 lb. per cubic foot.

4’ x 7” x 3” = 0.583 cubic feet.
0.5833 times 46 = 26.8 pounds.
There are two screws, so each will be supporting 13.4 pounds. Fudging a little for the weight of the hardware, let’s say 14 pounds.

At half extension (with a 3-inch thick jaw, 5.5 inches), there will be a
14×5.5 / 12 = 6.4 ft-lb of lateral torque on the screw.

I’m pretty sure that beefy screw can handle that. That leaves the connection at the rear jaw, which I don’t have a feel for (being new to woodworking).

If you’ve had the patience to stick with me, maybe you can help with whether the screw’s connector through the 1.75-inch thick rear jaw can handle that stress.

Thanks again.

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tnwood

204 posts in 1783 days


#3 posted 03-30-2011 02:44 PM

I just installed the Veritas twin screw vise and 3” of rock maple jaw, 24” in length. I don’t think you will have a problem with the weight of the face as it applies to the vise screws but you need to make sure the bench end is of sufficient strength to not be affected by the weight of the jaw face. The other thing I would be concerned with is the lateral force you may apply. Although I don’t have a lot of experience with the vise to date, it is my impression that there could be a strength issue with lateral horizontal forces if you clamp something way off center. The installation directions for the vise suggest a bearing board above the screws to keep them from sagging under certain conditions. I did not need to do this for my bench but can see where you likely would for a jaw of the size you propose. You can always try it and if it is a problem, cut the extra foot off both ends later?

View drewnahant's profile

drewnahant

222 posts in 1785 days


#4 posted 03-30-2011 07:01 PM

as far as the tendency of the veritas vise to drop at more than half extension, I would suspect that this is just an issue of slop in the fit between the screw and the female threads in their base pieces, I cant believe. In this case, there is a set amount of freedom, and adding weight will not increase it. I can’t believe that their design suffers from any sort of bending with just the weight of the wood and hardware on the end of it. I guess the only part where I could see bending being an issue, is by deformation of the wood on the bench where the base pieces are attatched, if that is the issue, I would suggest installing a steel frame in that area of the vse to distribute the load.

View Fellrunner's profile

Fellrunner

3 posts in 1623 days


#5 posted 03-31-2011 09:44 PM

Thanks to all for your comments.

I have another question, how much distance should I allow between the dogholes and the vise screws?

What I’m thinking about is sawdust and other benchtop junk falling onto the screw threads and fouling them. It seems to me that an inch and a half should be enough for the junk to dodge around the screws but that’s only a guess and I’d rather have your experience guide me.

CessnaPilotBarry,
your jaw comes to:
32” x 9” x 3” / 12 cubed = 0.50 cubic ft,
very nearly the same as my planned jaw.
If it worked for you without a bearing block, it should certainly work for me with a bearing block. I just like the idea of that block to steady the travel of the screw. In their instructions, Veritas shows examples of bearing blocks if you want to include one in your design.

tnwood,
My plan for the bench is to have the big twin-screw as the front vise and the regular-size twin screw as the end vise. I made the top somewhat massive (2.5 thick, 34 across, 85 long), and I’m planning a fairly massive base, or at least what seems massive to me. I wasn’t worried about the stability of the bench or its strength, but I’m taking your point to heart and will pull out my references (mostly Understanding Wood by R Bruce Hoadley) and calculator to make sure.

I’m mapping out the dogholes based on the placement of the vises (and their screws), and it would be a heartbreak to cut the jaw. I truly hope my planning will be thorough enough to avoid having to do that.

drewnahant,
Veritas mentions in their instructions that the lean-down is indeed due to the play in the threads between the screw and the base fitting. It’s generally necessary to have some play in gears for them to work properly, so the lean-down is routine because of the absence of guide bars. Kudos to Veritas for openly discussing the point.

I’m now confident that the hardware can handle the loads. My remaining concern is with, as you mentioned, distortion in the wood supporting the female-threaded base.

But as I’m writing this, I’m remembering last summer when I built a raised deck. The posts supporting the rails could be moved a little even though they were through-bolted to very solid framing with two 5/8 bolts. After I blocked them in, they were rock solid—couldn’t budge them at all. If I add support blocking to the skirt where the vise attaches, that should erase my concerns about wood distortion.

View gljacobs's profile

gljacobs

76 posts in 1384 days


#6 posted 03-31-2011 11:14 PM

@drewnahant where did you learn about the journeyman and master carpenters. Was it a book or something. It seemed very interesting and I’d like to learn more.
Thanks ahead of time.

About the original post I hope you post some pictures of this bench when you are finished with it.

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