Vise Jaw lift, is there an adjustment on PM vises?

@ErichKeane thanks so much! Think I'm going to see if I can set up my mill to do the inside of the nut. It looks pretty rough there. Seems I have acquired yet another project!
 
Thanks to this thread, I've begun to "fix" my el cheapo PM 4" vise. It has several problems, lack of sphere only one. The hole through the frame for the screw is not exactly on center, When you pull the jaw back it binds, also, the other end of the hole is apt (has) to get chips in it (packed so tight the screw won't go through.)
I'm going to
1) sleeve the hole for the shaft, after I center it and
2) fabricate some PVC tubes to cover the screw to keep chips off.

I've been looking for a project, think I've found one.
 
Had some time to look at this. If I understand correctly, the fixed jaw has to come off to allow the nut to slide out. Once the nut comes off, then, if desired, the screw can be removed. I moved the screw some and found there was a bearing unit in the housing.

How does the fixed jaw come off? I've tried tapping it with a small machinist hammer (brass faced) but it isn't moving at all. Is it just a tight fit on the rectangular key? No hidden fasteners? Just a much bigger hammer?
 
WobblyHand said:
Had some time to look at this. If I understand correctly, the fixed jaw has to come off to allow the nut to slide out. Once the nut comes off, then, if desired, the screw can be removed. I moved the screw some and found there was a bearing unit in the housing.

How does the fixed jaw come off? I've tried tapping it with a small machinist hammer (brass faced) but it isn't moving at all. Is it just a tight fit on the rectangular key? No hidden fasteners? Just a much bigger hammer?
Click to expand...
There should be a pair of socket head cap screws from the bottom holding it down.
 
Oh, I feel so embarrassed. Of course!

Ok, it's all apart. My half sphere isn't smooth on the sphere, or the flat. For that matter, the cavity is pretty rough as well. I was imagining it would be something a lot nicer. The cavity is not machined, it is rough cast.

No idea how one would polish the spherical part. Glue it to the end of a rod? It has turning ridges. It isn't smooth. Seems to be, surprisingly, 0.500" in diameter. After a little surface cleanup and some honing one can still see the big scratches in the flat surface. Looks like a crack that will continue to grow.
PXL_20210410_234300373.jpgPXL_20210410_234315511.jpgPXL_20210411_001836907.jpg
Is it possible to cut a ball bearing in half? How would one hold it?

The nut isn't that bad, considering. Part of it is unfinished. I will need to fit it together to see if that part actually needs finishing. Maybe it never hits there.
 
For the ball, it doesn't seem all that bad. Definitely better than my ebay one was. You likely would want to grind a ball bearing in half on a sander, and I'd hold it by drilling a hole in the end of stock and hot-gluing it in while you grind.

What I did on mine that was pretty bad was take an abrasive paste (auto part stores have it I think for prepping for paint), and just moving the hemisphere in there until it felt smooth. Then, I cleaned both and tossed a ton of moly grease in there.

I got most of my lift problems fixed by messing with the nut and making sure the front is smooth, the top doesn't hit the underside of the jaw, and that the angle was about a 45, on mine it was not quite right, so it was putting more force 'forward' than down. If anything, you might want the opposite. Also, the 'tip' of the 45 on the nut should never hit the inside of the jaw either, so you may wish to blunt that too.
 
I will get some ball bearings. Might use one ball and some valve grinding compound and rotate it about to make the pocket a little smoother. Somehow or another, I'll grind a ball in half. Thought I would use some steel tubing that is just under 0.500 ID. That way the ball would nestle in the tube. If I have to, I could either glue it or solder it to the tube.

My 3" toolmakers vise doesn't hold the nut very well. (And that's the only operative vise I have.) I need to mill some additional flats on the nut so I can clean up (mill) the 45 degree ramp. I think if I hold up the nut on some 123 blocks I can get the flats in.

Three weeks ago, I never would have imagined I'd be rebuilding my vise. Interesting hobby, never know where it will take me...
 
WobblyHand said:
Is it possible to cut a ball bearing in half? How would one hold it?
Click to expand...
Given how hard ball bearings are, I think you may need to grind it.
Use a close match ball mill on the end of a ?brass? rod. Make the pocket a little deep so you can crimp it around the ball after you glue the ball in with epoxy or permanent Loctite. Dress your abrasive wheel so it is sharp. Since heat can release the glue you will need to keep dunking it in water. Use the side of the wheel to make a flat. Yes, & no you shouldn't use the side but light pressure and just enough grinding to clean it up should work. Duck if it disintegrates!
 
A belt sander makes short work grinding ball bearings if you can find a good way to hold it. I wonder if a neodynium magnet buried in a tube would work?

I hope you can grind or lap the pocket for the ball well enough to house the ball without too much slop.
 
I'd probably clamp the BB in the edge of a vise and run a slitting disc through gently. It doesn't need cutting right through the centreline. If you can find a carbide burr or spherical stone the right size you should be able to get the dimple sorted well enough without much fuss too.
 
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