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

After 2 seconds of observation, I realized I could use the toolmakers vise to hold the nut upside down. I then milled flats on the top side so I could hold the nut at 90 degrees. I ran a mill just kissing the flat at the end to smooth that end. Just shaved off 0.001" enough to take off the tool marks. Prior to that I checked that the "flat" was perpendicular to the table. Surprisingly it was pretty good.

Roughly measured the ramp angle, it is very close to 45 degrees, but it is not square to the vertical axis. There's about a 0.04 gap at the top relative to the bottom, as measured with a square referenced to the fixed jaw top. I'd bet in practice this doesn't matter, as the ball takes up the error, but it's annoying.

Next step is to tram the toolmakers vise to 45 degrees so I can take a cut on the ramp to clean it up. I have a 45 degree angle block so that won't be too hard. The milling cutters I have aren't long enough to cut the ramp in one pass. I need almost 1.5" LOC to do it in a single pass.

A bit apprehensive about lapping the pocket. It will be tedious at best. Maybe a single cut spherical burr would be better and faster. As I understand it a single cut is slower and more precise.
 
WobblyHand said:
After 2 seconds of observation, I realized I could use the toolmakers vise to hold the nut upside down. I then milled flats on the top side so I could hold the nut at 90 degrees. I ran a mill just kissing the flat at the end to smooth that end. Just shaved off 0.001" enough to take off the tool marks. Prior to that I checked that the "flat" was perpendicular to the table. Surprisingly it was pretty good.

Roughly measured the ramp angle, it is very close to 45 degrees, but it is not square to the vertical axis. There's about a 0.04 gap at the top relative to the bottom, as measured with a square referenced to the fixed jaw top. I'd bet in practice this doesn't matter, as the ball takes up the error, but it's annoying.

Next step is to tram the toolmakers vise to 45 degrees so I can take a cut on the ramp to clean it up. I have a 45 degree angle block so that won't be too hard. The milling cutters I have aren't long enough to cut the ramp in one pass. I need almost 1.5" LOC to do it in a single pass.

A bit apprehensive about lapping the pocket. It will be tedious at best. Maybe a single cut spherical burr would be better and faster. As I understand it a single cut is slower and more precise.
Click to expand...
so, I was thinking about the lapping... If you are going to get a steel ball to cut in half, buy 2. Attach the 2nd to a bar in some way (welding? Soldering? etc?), put some abrasive compound on it, and fire up your drill and use that instead. A burr might take too much material and not leave it smooth enough. You don't care if it is perfectly flat, just that the ball can tip side to side/up/down with a minimum amount of force. You also don't want to take too much material off, because if the half-ball sits too deep in it, your nut will hit the jaw instead of staying in the ball.
 
Oh, I had to buy a bunch of ball bearings... Didn't have much of a choice, and shipping was practically the same anyways. So I'll have 50 to play with. :) So when some of the balls go flying off when grinding, I won't have to search for them with the same sense of urgency if I only had one. :p Power lapping (with additional random motion) is a possibility if I can somehow attach a rod to the bearing. The vise is trammed to 45 degrees, which wasn't that hard. I'm less than 0.001 off over a few inches of travel. That's way better than how the ramp was machined.

This beginner doesn't have the full complement of tooling to attack the problem at hand. So I'll wait for stuff to dribble in. It will take less than a week. There's no shortage of other projects here to keep me occupied. Have to say this project has been fascinating for me. I did order a single cut burr, which is for slow removal and better surface finish. I'll just kiss it to the surface by hand and see what it looks like. Can't be a lot worse than what is there now. (It looks more like a dimple than a spherical surface)
 
Have the ball bearings, the burr, and some steel tubing. As well as an end mill with 1.5" LOC. Cut off a piece of tubing and lightly bored it out so the ball diameter just fits below the surface. Was getting a little late, so didn't press my luck with grinding the ball. Have to change out the belt to ceramic anyways. Tomorrow should be an interesting day. Probably take a couple of tries to get sufficient grip on the ball.
 
So far the ball grinding is going surprisingly well. Must be beginner's luck! Right now the ball measures 0.330" from the truncation flat to the spherical part. How close to 0.250" do I need to be? The original (which I did polish) is very close to 0.251" but I'm not sure I trust that dimension - after all, the vise isn't a showcase... I've dykemed the tube to make a mark on it so I have some reference mark. Not sure if I should remove 0.060, 0.070 or 0.080.

It's pretty easy to grind as I have the ball inset in a tube. The tube makes a great handle. No adhesive, no solder, just a light press fit. I use a punch to remove the ball from the tube. I just apply light pressure to the tube against a ceramic belt with a pyroceram platen. With the ceramic belt there's no heat issues, it cuts very nicely. Initially started grinding with a 60 grit belt and later switched to a 80 grit belt. I'll clean up the grinding marks later with diamond stones. I found if I slowly rotate the tube, it seems to clean up the grinding marks a little. Unfortunately for the picture below, I reverted to straight "push it in" mode as I needed to remove more material.
PXL_20210414_135713096.jpg
 
I don't think it being a half-ball is particularly important, just that it sits proud of the cutout in the jaw when in place, and has a smooth flat for the nut's 45 to run on.
 
Great. I just checked the ball in the "dent", it's definitely proud to be there :p It moves in the socket pretty nicely, even without grease. Already an improvement. Not grinding off too much gives me a little more latitude in cleaning up the pocket to make it smoother. The smooth face is already 0.470" in diameter, so the area is only 13% less, than if it was ground to half diameter. Guess I will hone the flat and move on to cleaning up the ramp.

Not really sure if the nut is square in the vise. I am using the "square" cut as the reference side and have placed it against the fixed jaw. On the movable jaw I have a piece of aluminum TIG rod to be a little squishy. Dead blow hammer set the nut into the vise. It seems the square cut may not truly be square. Have any suggestions? (Picture was taken before adding the wire.)
PXL_20210411_235246175.jpg
 
Thats almost exactly how I held mine, I used the vertical 'rail' as my indexing surface for that, which is the only one that matters. If the angle is less/greater than 45, it doesn't particularly matter. 45 is the 'magic' number because it produces an equal amount of force down and closed, but if you were 'smaller' than that (in reference to the top surface) you'd get less clamping force, but more 'down' force (and vice-versa).

So in your case, the only meaningful 'index' is that you're square to the vise 'horizontally', that is, parallel to the table. The rails aren't perfect for indexing, but are as close as you have (as you REALLY care about parallel to the lead screw).
 
Looking good. The ball on my shars vise was much more polished than yours, but the socket was in poor shape. I figure the ball is there to account for variations in both surfaces, so I'm not sure how critical it is to have the surfaces exactly at 45 degrees.

image045.jpg


Compared to the accuracy issues in the grind of the vise and the fit of the jaw to the body of the vise, I doubt the ball on mine has any impact on accuracy. Scraping resolved my fit issues.
 
macardoso said:
Looking good. The ball on my shars vise was much more polished than yours, but the socket was in poor shape. I figure the ball is there to account for variations in both surfaces, so I'm not sure how critical it is to have the surfaces exactly at 45 degrees.

View attachment 362638

Compared to the accuracy issues in the grind of the vise and the fit of the jaw to the body of the vise, I doubt the ball on mine has any impact on accuracy. Scraping resolved my fit issues.
Click to expand...

Right, the ball is simply so that the 'interface' between the jaw and the nut is flexible. The angle just controls the 'vector' of the force applied by the nut. The inside of the jaw is simply clearance so there is enough wiggle room between the two to not bind.
 
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