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View Full Version : bench vise (vice) nut retaining pin?



metalmagpie
06-29-2012, 08:34 PM
I am cleaning up a large (150+ lb.) bench vise (I'm going to use the US spelling, apologies to the many people who spell it 'vice'). It is like other vises I have taken apart. The moving jaw is pulled towards the fixed jaw by an ACME screw. That screw threads into a nut which is made from a separate casting from the main vise body. That nut slides axially into a blind dovetailed slot; the blind end towards the moving jaw. As the screw tightens, the nut bears against the blind end and thus cannot move, so the screw end has to move in the direction of tightening the vise. All with me so far?

Now, to open the vise jaws, you unscrew the handle. The nut wants to move away from the handle, but it can not because there is a pin through the vise base which sticks up into the vise body and prevents the nut from moving in that direction. Thus the screw (and fixed jaw) move away, opening the vise.

Now, this vise came from a guy who was a great welder, but who didn't really understand how the vise was supposed to go together. The vise had been painted at least once before, thus fully disassembled, and my guess is that at some point someone lost the vise nut retaining pin. The welder looked at the nut, saw a "foot" sticking out of the back of it, didn't see what it was for, and cut it off with a grinding wheel. Thus my nut has the entire threaded area intact, but its base is now about 3/4" shorter than the distance between the pin and the blind end of the dovetail. Which leads to an intolerable amount of backlash in the thread. He had tried to weld the nut in place, only the weld didn't work due to his using the wrong rod. He gave up and sold the vise. His loss, my gain - I hope!

I have two questions.

First, the pin hole in this vise isn't vertical. Nor was the one in the Reed vise I took apart some time ago. Both were tilted maybe 8-10 degrees back from a plane normal to the vise base. I realize this hole may have been done with a hand drill, but still, a tilt of that magnitude seems unlikely to have been done by accident. Can anyone explain why the hole they put the pin into which retains the vise nut isn't vertical?

Second, is there any reason I can't simply drill a second hole right behind the vise nut and push in a 1/4" spring pin?

metalmagpie

Boostinjdm
06-29-2012, 09:46 PM
I've rebuilt a few vises and know exactly what you are talking about. I personally would make a new nut to fit, extend the old nut, or make a spacer block. I would not drill a new pin hole.

I have brazed the dovetails and filed them for a perfect fit on all my rebuilds so far. I makes a difference in how the vise feels during use.

TGTool
06-29-2012, 09:47 PM
Wouldn't the slanted hole and pin cause the nut to move towards the solid casting in the event there was clearance in the slot which would minimize the bending moment on the pin and attempt to keep it in shear?

metalmagpie
06-29-2012, 10:01 PM
Wouldn't the slanted hole and pin cause the nut to move towards the solid casting in the event there was clearance in the slot which would minimize the bending moment on the pin and attempt to keep it in shear?

The nut either bears against the (very solid) blind dovetail end, or against the pin. One while closing, the other while opening. Having the pin slant away from the nut would cause the back end of the nut to want to raise up, sliding up the pin, which it seems to me would increase the bending moment, not decrease.

metalmagpie
06-29-2012, 10:04 PM
I've rebuilt a few vises and know exactly what you are talking about. I personally would make a new nut to fit, extend the old nut, or make a spacer block. I would not drill a new pin hole.

Why not drill a new hole?


I have brazed the dovetails and filed them for a perfect fit on all my rebuilds so far. I makes a difference in how the vise feels during use.

I thought about that. What I was considering was a shim under the nut, forcing it up against the dovetails. That dovetail is just roughly cast, although with heavy cross section. It would be challenging to make it fit really closely.

metalmagpie

Boostinjdm
06-29-2012, 10:44 PM
New hole just doesn't feel right to me. Getting the dovetail to be tight did take some trial and error. I got it to slide with a slight push to within a 1/4" of being home. Then paint up everything and do the final install with a hammer. My vises have as little slop as possible and I really like them that way.

lakeside53
06-30-2012, 02:54 AM
I just took one apart. Same crude cast body dovetail, and I'm pretty sure my pin hole was a at a slight angle, and the pin bent even more as it was rammed in so it jambed the entire nut assy forward tight into the dovetail.

So long as the remaining nut dovetail can still insert into the body dovetail, no reason you can't drill a second hole. You could add to the existing dovetail also. Not sure why you need to "shim up" -the dovetail will lock if thust forward by the pin and have enough vertical movement/slop for the screw/movebale body alignment. As long as it's jambed forward, you'll have low backlash.

I'd use a solid pin.

metalmagpie
06-30-2012, 08:19 AM
I just took one apart. Same crude cast body dovetail, and I'm pretty sure my pin hole was a at a slight angle, and the pin bent even more as it was rammed in so it jambed the entire nut assy forward tight into the dovetail.

So long as the remaining nut dovetail can still insert into the body dovetail, no reason you can't drill a second hole. You could add to the existing dovetail also. Not sure why you need to "shim up" -the dovetail will lock if thust forward by the pin and have enough vertical movement/slop for the screw/movebale body alignment. As long as it's jambed forward, you'll have low backlash.

I'd use a solid pin.

Hmm. Maybe they used a soft pin, and peened it forward against the nut, driving the nut in solidly and at the same time jamming the pin in its hole so it can't move unless driven out from the bottom. In which case the angle would be to make sure there was some room for peening.

MM

lakeside53
06-30-2012, 12:28 PM
Mine was angled towards the back of the vise... so it slid onto/by the rear nut body. Soft pin just banged in from below and it "bent" towards the rear by pressure on the nut.

EddyCurr
07-01-2012, 03:14 PM
I have a 6" Gray Mechanics Vise that is disassembled for pin
replacement. OEM parts were obtained from Gray.

Would photos or measurements of anything be useful?

.

metalmagpie
07-02-2012, 05:08 PM
In the end I just drilled/reamed a new hole and pressed in a 0.250" ground pin. Job done. FYI I held the vise upside down on two short stepladders and used a mag drill to keep everything lined up. Nut now nice and solid.

metalmagpie