[elalto]

Hi All,

I have a number of vises for my mill/drill and they all do the same thing, they push one edge of my work piece up as they get tight. This is driving me to drink!

What can I do? how can I secure my workpiece with out having the fixed jaw side .0065 higher than the moving side? I have bought several "great" vises and they all do the same thing.

HELP!

Thanks in advance for any advice i can get.

Marcos (elalto)

[ballendo]

Hello,

Not really "great" vises, are they?

This is a common problem, and the Kurt style vise is designed to overcome it. There are asian copies of the Kurt. Some love 'em, some hate 'em. But they do have the hold down feature that most "drill press vises lack.

What to do about your situation?

Before the kurt style vise was widely used, machinists usta use a lead or brass hammer to seat the part in the vise after tightening. Still works...

But, have you considered doing some machining on the vises you have to improve matters? (You won't get it perfect, but you can certainly get it better than 6.5 thou, IMO.

After all, if the fit is made better between the jaw and whatever its riding on, it can't "come up" as much. If it's the steel rod type, simply bore and insert bushings. If it's a flat "box" way type, adjust the fit with shims or similar "adjustments"...

Hope this helps,

Ballendo

P.S. Nowadays a dead-blow plastic hammer has largely replaced the brass or lead types. And try to use only enough force to hold yor part securely. It's VERY easy to move the "fixed" jaw of a cheap vise with the pressure available FROM THE SCREW AND MOVING JAW...

Originally posted by elalto
Hi All,

I have a number of vises for my mill/drill and they all do the same thing, they push one edge of my work piece up as they get tight. This is driving me to drink!

What can I do? how can I secure my workpiece with out having the fixed jaw side .0065 higher than the moving side? I have bought several "great" vises and they all do the same thing.

HELP!

Thanks in advance for any advice i can get.

Marcos (elalto)

[HuFlungDung]

Even with a Kurt (or a clone) vise, you still need to seat the part into the vise with a special "graduated hammer" blow as Ballendo laid out. But this is not the cause of your tilt problem. Even in a good vise, the part will tilt if the front and back surfaces of the part are not paralled in the vertical plane of the vise jaws.

You should always use parallels under the part, whether these are precision parallels or even cold drawn keystock. By situating one parallel near the front and one near the back jaw, you can test if the bottom surface of the work is nesting properly on the two parallels, by attempting to pull them sideways. If they are both tight, then you have a good seating. This is also an excellent way for the beginner to learn to hammer properly. Too much force will cause the piece to bounce off the parallels. It takes just the right amount of force sometimes to make it perfect.

I still prefer a lead hammer to a plastic deadblow, because the lead is more dead. However, lead is a toxic pollutant, and you can easily contaminate your fingers by merely touching it.

Now, the tilt problem: its like the proverbial chicken and egg thing: you want to make a part with squared surfaces, but to do it, the stock needs to be square to start with.

Actually, though, there is a trick to use, even if your stock is not very good to begin with. We will assume that the back jaw of the vice is perfect for this discussion. If it isn't you can shim it to perfection by checking its vertical plane with a dial indicator in your non-rotating spindle.

Okay, when that is good, then get yourself a piece of round rod about as long as the vise jaws are wide. Place this piece of round bar stock between your workpiece and the movable jaw. Snug the vise closed, keeping the round bar about midway on the workpiece. Then, commence to hammer the workpiece down onto the parallels.

The principle in use here, is that the round stock provides a single line of contact with the movable jaw, and the part can tilt in front of it. So then, it seats firmly against the rear jaw.

One other trick to check up on, is the deflection of the rear jaw of the vice. Place your dial indicator against the back jaw and tighten the vise. You may be surprised to see it move a thousandth or two, but it will. If you are really extreme in the force you apply, you can get differing part locations with every clamping. So learn to use a consistent force for a given part.

BTW, do not tighten the vise any more after the last hammer blows. You can apply pressure to the handle to make sure it is tight, but don't try to tighten it some more. Over-tightening can lift the part off the parallels again, as your vise bows from the force.

Furthermore, if the part has no machined surfaces, do not worry about seating the bottom surface on the parallels until it is one of your previously machined surfaces. But you knew that

[ballendo]

Hu,

That's an excellent post!

Ballendo

[elalto]

Great advice,

I do have a Kurt clone, the moving jaw is or was a little off verticle square. I have tried the dead blow hammer trick before but still have the problem.

Today I tried putting a doubled piece of notebook paper on the low side, on top of the parallel and under my workpiece seems to have dropped the difference to .0015. I think I can live with this at least until I get a real mill (can you say Bridgeport?).

Thanks again,

Marcos (elalto)

[SRT]

Thought for the day:
You can't make a silk purse out of a sow's ear.

[Swede]

SRT is right. Over the years,. I've had the following vises in use at one time or another

3" Kurt
4" chinese
5" Kurt, 5" Chinese
6" Kurt, 6" Chinese

I still have all of these vises. EVERY Chinese Kurt clone has been innaccurate, either with the vise keys at the bottom of the vise, or the jaws are unven, the bed is not parallel with the base, etc etc. EVERY Kurt vise, no matter how stained, rusty, or decrepit, has amazed me with its inherent accuracy.

Recently I bought a 4" Chinese Kurt clone for my CNC mill project. Everything about it looked great until I applied an indicator to it. It was sickening how bad the vise was. But boy it looked nice, good paint, pretty ground jaws.

Disgusted, I bought a nasty-looking 3" Kurt vise (very rare, I don't think they're made anymore, cute little vise) for $200, twice the price of the 4" vise. Cleaned it up with some steel wool and oil, and installed keys. Once again I can grip stock and mill away, knowing the piece will be parallel and true to within 0.0005" over it's entire work envelope, and near 0 for smaller work pieces.

Moral... don't even bother with the Chinese vises. Maybe someone has had better luck than me, but 3 different Chinese vises is a pretty representative sample, and they all sucked.

Swede