Adam, do you have a minute?

Re: Adam, do you have a minute?

Adam Cherubini, NJ

>Frank,

Screws

I use 1-1/2" dia 6 thread screws for my bench screws. The heads are approx 3-1/2" in diameter. The large head is one of the keys to the success of the twin screw. It is under the head that I apply pressure, not in a couple between jaw and screw shaft.

Nuts

The nuts are rectangular blocks of lignum vitae, cross drilled and tapped. I worried about the perpendicularity of the hole to the front face. Lacking that would cause the nuts to induce a moment in the screw that would at least increase friction. If I recall correctly, I bored and tapped the hole, then screwed the nuts onto a dummy screw, mounted the whole mess in my lathe, and cleaned up that front face. I'm betting you'll have a better way to do that (possibly called a drill press).

Jaw

The jaw is a loose fitting affair. Holes through the jaw are 1-3/4" dia. When you make the jaw, just don't make the mistake of marking the holes too high (as if the big clearance holes will be centered on the screws). Remember the jaw will hang down on the screws. The top surface of the jaw should be just below the top of the bench. My jaw is not angled in any way. I don't agree that this is a good idea. It should be thick and strong. My screws are 18" apart, so if you put a hammer handle between them, you could bust something. I recommend at least a 2" thick jaw. Mine is riven beech. Oh, and the jaw should be not much deeper than the screw heads. Jaw above the heads, does nothing for you. There is no pressure there, only behind the heads. Jaw beneath the heads does nothing but make the screws sag and the vise heavy.

Bench integration

The trick here is getting those large heads as close to the top of the bench as possible without going above (because that would interfere with planing operations). This way, very narrow stock may be worked. Vise pressure is just behind those heads, so getting them high up is good.

There are various ways to accomplish this. The front 16" of my bench is 4" thick. I bored an 1-3/4" hole 16" deep (into beech) with a framing auger. You could cut a tunnel instead. I didn't want to cut a tunnel because I didn't want to lose section (moment of inertia). But you could cut a trench then restore the lower cap (of the I-beam) by screwing on a board or steel plate or something. The screws are supported vertically, in my case, by the hole. You'll have to do that somehow as well. You could have a tightish hole through a front apron and a long wear strip at the bottom of the trench (on top of the screw).

The nuts sit back 6 or more inches from the front of the bench. I did this so the vise wouldn't break the bench. The side advantage is the screws have no threads on the last 7 or 8 inches (6" to the nut + the thickness of the jaw) This is nice because the work can sit down on top of a smooth shaft. No reason to sit on threads. The nuts are housed in loose pockets. When you remove the screws, the nuts fall out. A little slop here is good since the nuts will align themselves as they wish. No reason to force them into one place or another.

I made my screws much too long (easily enough fixed). Removing the vise takes a minute and I never clamp anything thicker than 4" or so. I never have need to.

Conclusion:

A twin screw vise is a simple set-up but does require some thought. Be careful and it will work better than anything you can buy. It really is a very effective design.

Alternatives:

If you want a traditional style bench for the purpose of educating, I'd recommend no vises. Much can be done and learned with a simple crochet and planing stop. Also, I'm finding value in low benches for children, Most lack the upper body strength needed to plane successfully. A really low bench might help. If you have your heart set on including a twin screw vise, consider putting it in the middle of the front face (as Moxon shows). There's no reason why it must be located on the left side. And definitely leave the right end tail-vise-free so you can teach sawing there.

Adam

Leg vise solution

Matti Kuikka

>Frank, I think that you could make a leg vise by adding another "leg" to your trestle that is flush with the side of the bench, extends to the top of the bench and is anchored to the trestle top and bottom. The jaws would be the new leg and the proper leg vise. This way you could also redress/renew jaws if damaged which is also a consideration especially with young boys. Just my 0.02�.

Matti Kuikka

P.S. Mine are 6(girl) and 5(boy) and we have only used my bench for sawing with japanese saws, yet.

Re: Leg vise solution

Frank Mutchler in Colorado Springs

>I don't think I can do that with the present construction. This is a pic of one end, dry fit.

Mortises are not yet cut for the stretchers, nor is the bottom of the foot contoured.

Re: Leg vise solution

Matti Kuikka

>Sorry,Frank. In the earlier picture about building memories the construction was still straight as in old benches and it would have been easy, now you would change the aesthetics if you tried to make a leg vise.

Matti

Source for 2" wood tap and die sets... *LINK*

Sandor in Boyds, MD

>Here is a real bargain for the guy wanting to build his own 2" x 2.5 TPI vice hardware : )

At 907 Euros, I'll think I'll pass.....

http://www.fine-tools.com/gewind.htm#zield12




http://www.fine-tools.com/gewind.htm#zield12