truing a milling vise

[Driveslayer45]

i have recently discovered that my no name 4" vice has .003 variance on the x axis and .001 on the y. i am thinking of turning it upside on 123 blocks and facing the base on my milling machine. is this a reasonable course of action or should i just replace the vise. i would rather not spend $200+ on a vise if i don't have to.

 

[Flyinfool]

Before you start carving on the vice, make sure it is the vice that is the problem.
Double and triple check to see that there is not small burr or chip between the vice jaws and the surfaces that the jaws mount to. then make sure that there are no burrs or chips on the mill table or the bottom of the vice.
It is real easy to raise a microscopic burr on the bottom of the vice or the table top. Do some light stoning of both to remove any burrs or dents, Evey dent or scratch will have a raised area right next to it. the metal from the dent had to displace and go somewhere. same with the jaws, lightly stone the mating surfaces.
Also check to be sure that you are using the correct side of the keys to bump the vice to the T slots, and make sure that there are no burrs on the sides of the T slots either .

Once you are absolutely sure that the vise is the problem then go ahead and machine it. But be absolutely certain that your head is trammed in perfectly or you will machine in new errors. Do not trust the tram job you did six months ago. All it takes is one chattering or interrupted or heavy cut to move it.

 

[Winegrower]

Excellent advice from Flyinfool. I did pretty much this on an inexpensive vise and it came out perfect. Have at it.

 

[Driveslayer45]

Yes, great advise, thank you.. i did run a stone over the bottom of the vise and clean the mill surface very well before placing the vise. i did not remove the jaws and clean them, but as i am measuring the vise bed that shouldn't have an effect.

I am not sure what you mean by this "Also check to be sure that you are using the correct side of the keys to bump the vice to the T slots,"

Perhaps i will pull the vise and re-clean, check and maybe stone the mill table just to be sure, but otherwise i am thinking of cutting. Also I recently trammed the mill, right before the current project, but as i am using a test indicator clamped to the quill the tram shouldn't matter should it.

 

[Latinrascalrg1]

Is there a way for you to mount the vice to a "sacrificial" intermediate plate that is then mounted to the mill table? Mill the sacrificial plate to correct the misalignment issue without modifying the mill or the vise if you have the z axis travel space!

 

[Driveslayer45]

that's in interesting thought that i had not considered. i would have to figure out how to offset it by the .003 and .001. but would that introduce another set of possible errors into the mix?

 

[Latinrascalrg1]

I dont think you would have to adjust for any offset currently in the vise. If the head is trammed i would think securely mounting the sacrificial plate to the bottom of the vise and then mount the vise to the bed using the vise jaws clamped squarely onto some 123 blocks (maybe?) So that the jaws are square to the table and then do your milling of the bottom surface of the sacrificial plate that should now be face up attached to the bottom of the vise! I haven't done this before and just kinda thinking outside the box.

 

[C-Bag]

Just out of curiosity you've set it up on a surface plate and checked it? I learned the hard way not to put all my trust in one place. Especially a machine table.

 

[Driveslayer45]

i see what your are saying L, that makes sense.

C. I did not use a surface plate .. i ran a test indicator from a quill clamp across the vise in the X and Y planes, saw the deviation, then traversed over and lowered the quill and ran the X and Y planes directly off the mill table. i figured doing that would eliminate any deviation from the machine itself. Assuming what I really care about is the correlation / interaction between the quill and the table.

I have my vise mounted to the left 1/3 of the table so i can use the right 1/3rd for table mounted work.

 

[Flyinfool]

How are you aligning your vice to the x axis? Some vices have keys sticking out the bottom to bump up against the key slots to save time in having to bump the vice around to square it up. Sometimes only one side of the keys is a precision surface.

Defiantly stone the mill table also. Stoning should always be done to both sides of the mating surface. It is amazing once you find just how small of a dent can mess things up.
Take a small piece of scrap and make it smooth and flat on one side. Then put in a small dent from the corner of another piece of steel. Once you stone it back to flat you will be able to see the different surface finish to show what was the raised area around the dent. It will be bigger than you expected.

The tram is important because if it is off at all then you will not be cutting a flat surface, depending on the direction that the tram is off, you will be either cutting steps, or concave grooves, or a combination of steps and grooves.

Since the vice is not mounted in the center of the table it is also possible that with all the weight extended out one side that the table is shifting in the gibbs and sagging down on one side. Is by chance the low side of the vice the same side that the table is sticking out?

When checking the vice compared to the table you want to check the same place on the table as where the vice is.