I believe the shaper vice screw is under tension while a 'normal' vice screw is under compression – I have a shaper and such a vice and I believe the theory is that when planing in the screw axis with a compression screw, toward the screw, the cutting force may work against the compressed screw, thereby releasing the vice jaw pressure and allowing the work piece to move.

I am not sure why there is a supposed better chance of compressing the screw as opposed to stretching it if under tension..

Joe

I think the point is the fixed jaw is at the front of the machine, so the cutting force is into it. Then when you think about getting the screw handle to be also at the front for convenience of operation you end up with the moving jaw having to be pulled towards the front – hence screw under tension.

Do you mean 'pushed towards the front' ? ( by the shapers stroke)

Also, I would like to see the typical large milling vise screw fail by kinking when used one the shaper!

Edited By Joseph Noci 1 on 10/03/2020 17:28:52

Seems nobody told Boxford about the need for a "special" shaper vice :

Original swivelling vice on an 8" Boxford shaper – not had anything come loose while using it. Maybe the machine is not capable of stressing the "conventional" vice used ?

Nigel B.

I just took a look at my shapers to see what is what. The 18 inch Alba has the arrangement that puts the screw under tension. The 10 inch Alba does not, the screw will be under compression. Those are both original vices. The Ammco shaper does not have an original vice, but I have the drawings and that would put the screw under compression.

I think the main feature of a shaper vice is that they are usually low profile.

I don't think that the cutting forces on a shaper are any higher than with anything else, the only point you should watch is when the cutting force is along the vice jaws, when it may move the job. A piece of paper between the jaws and the job is enough to prevent this.

John

You could easily simply correct that mistake by using the ‘edit’ option?

Seems nobody told Boxford about the need for a "special" shaper vice ….

Yes, others too. The screws of some low-profile vises on the likes of Drummond were in compression. There is a securing bolt, tightened down, after securing with the item with the jaw screw, on the Drummond vise.

I suspect the screw usually being in tension for shaper vices was more a case of following the way its usually done than the result of careful mechanical analysis. Somewhere during the early development process screw in tension was a feature of shaper vices that were known to work well and, therefore, became popular so folk stayed with what was considered a good design. Most especially if some attempts with screw in compression were found unsatisfactory. Even if that were due to reasons other than the screw arrangement.

The generally low profile trend may have influenced things too.

Back in the day many milling vices with screws in compression had the screw mounted externally pushing against the moving jaw. Usually fairly high up to give some anti-tilt effect. Seems that might have been a less costly way of making a vice albeit slightly less strong and inherently a little taller. So perhaps the underslung, screw in tension, arrangement also signified a better quality and therefore worth paying more for vice.

Far as I can see there is no engineering reason why the cost of making screw in tension and screw in compression vices should be significantly different. But if you can charge more for one type that is the type that will get made. Heck if you could convince the factory owners to pay more for pink ones everything would be painted pink and shop floor groans about the new stuff being too girly ignored.

Shaper and planer cutting forces are continuous so may well take more withstanding than the more intermittent cutting loads of the successive teeth of a milling cutter. Could well be larger in practice too. A big shaper or planer can take seriously hefty cuts. Even if it can't match a big horizontal mill with a nice set of ganged cutters for sheer speed with which it buries you in chips.

Clive

If the handle of the vice is pointing away from the ram, (It would be difficult to have a conventional vice sited so that it points towards the ram ) on the normal, outward, cutting stroke, the screw of the vice will be under compression.

The action of clamping the work will subject it to compression, anyway.

You could mount one of the Precision Vice, Type 2, as sold by Arc Euro. On this, the cutting forces are resisted by a round bar clamped into a slot. In this, the clamping screw is in tension, since it is pulling the bar into the slot, but not subjected to cutting forces.

Since it will see little use, and would cost more than I had paid for my Adept No.2 Shaper, I made a cheap, soft, and probably not very precise, version out of whatever material happened to be lying about.

How it was made is shown in the article in MEW 290

Howard

Perhaps you could explain this phenomena.

The Edit function is time limited – a 20 or 30 minute window from posting IIRC, then the function is removed.

Nigel B.