Hole size for twin screw:

Re: Hole size for twin screw:

Warren in Lancaster, PA

>For the holes in the vise jaw you want the major diameter (around 1 3/4). This should be fairly tight so the vise doesn't wobble. You can measure this from the outside diameter of your tap. The part of the screw in the vise can be a little larger than the rest in order to make a nicer fit with the hole. If it ends up too tight you can turn the screw down a little. For the holes in the bench you want the minor diameter (around 1 3/8). You can measure this from the inside diameter of your screw box.

If your threading kit was made in Europe, it was probably designed around metric sizes; you may be better off buying metric bits. I think it would be worthwhile making a small practice screw before buying the bits.

correction

Warren in Lancaster, PA

>I misread your measurement. The larger diameter is about 1 1/2 and the smaller is near 1 1/4.

Re: Hole size for twin screw:

Adam Cherubini

>I didn't fully understand Warren's message I guess--I jut measured my bench. Now i have the 1-1/2 taiwanese tap and die set. I turned 1-1/2 dowels then threaded them. The finished threads are 1-7/16". The holes in the bench are 1-1/2 full.

Forget about all that tho: Are these holes clearance holes in some sort of apron? What is responsible for reacting sag? Are there some guides under the bench top or something? If so the size of these clearance holes matters less than their position(non concentric).

On my bench, the top is one solid hunk, 4" thick and I simply bored holes right into it. 4" back or so I chopped a recess for the nuts into the bottom (intersecting the bored holes). So those holes are like 16" deep, bored with a ship auger. That was one heck of a hole (actually two).

Adam

Re: Hole size for twin screw:

David Hammond, in Powder Springs GA

>The holes are going to be bored directly into my top, like yours Adam - my top is 5 3/8" thick at the moment, SYP, and I'm planning to bore the holes before glue up, as well as cut the mortises for the nuts before the glue up as well. I realize I'll need to adjust the vise jaw cocentrically to allow it to end up flush with the top of my bench, b/c the holes in the vise jaw will be larger than an 1 1/2" b/c the vise won't have garters.

But I think you answered my q: if the threads end up 1 /7/16" in diameter, an 1 1/2" hole bored into my bench, 16" deep or whatever, should be what I need, right?

Tia.

David

Re: Hole size for twin screw:

Warren in Lancaster, PA

>I was thinking that since David bought a threading kit and not just a screw and nut, he could just cut threads into the benchtop and not bother with inlaying a nut. I've seen benches set up this way. Perhaps there are problems with this approach that I can't see.

Interesting

Adam Cherubini

>That's an atypical approach and there are host of technical problems associated with it.

First, the tap, like David's forstener, has a limited depth of cut. Boring holes in inidividual boards, then gluing them together will work fine for David, but tapping those holes individuallly would be harder. You would need to clamp the previously tapped board onto the to-be-tapped board to ensure your threads lined up.

Once completed, alignment would necessarily be much more accurate. You could make sacrificial screws, wax them so they don't get glued in place, and use them to help align things. Keeping glue squeeze out off the threads during glueup would be another issue.

The next problem of course is that David's bench material wouldn't be a great choice for a nut. Even benches like mine where the bench top would make a good choice for a nut (beech in my case), threading the bench top removes the chance for replacemnt of the nut.

That said, I threaded one of my bench's legs directly for my leg vise, thinking I could always inlet another chunk if need be.

So rather than saying this isn't a good idea, its better to say one should address all the technical issues before attempting this.

Adam