truing a milling vise

I align the vise with a dial indicator, or test indicator, hanging from the quill with a mag base or quill clamp. then i index off of a tall parallel clamped into the jaws, running the table back and forth and tapping the vise base with a hammer. i shoot for half thou over the 6 inch parallel. The vise came on a swivel base which I've pulled off so get a better mounting to my table. figure one less item to throw off my work.i have not tested it with the swivel base installed.

"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." <-- can you recommend a stone. currently i use an old sharpening stone but its not precision in any way so i rub it very very lightly.

"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 gibs and sagging down on one side. Is by chance the low side of the vice the same side that the table is sticking out?" <-- you know i hadn't considered that thinking the machine would be able to handle it but yes, the left is the low side and the vise is centered over the left 1/3rd of the table.
 
If your vise is mounted on the left third of the table, the right side of the table should be hanging out in air when you scan the vise. If the table is moved far enough to place the center of gravity past the support of the ways, the table will pivot lifting the far side up and pushing down at the pivot point. This will lift the left side of the vise relative to the right side.

Note that this effect will happen on the x direction with both the x and y ways. Most mills that I have seen are fully supported in the y direction unless there is a significant weight overhanging in the front.

You can assess this effect fairly easily by mounting an indicator external to the table and sweeping the table. The mount is conveniently done with the quill or the spindle but any solid surface can be used. If the mount is made to the y axis saddle you can separately assess the effects of the x and y axes. Lifting can be reduced by tightening the gibs. If you have a thousandth play in the gib, you will potentially see about 1.4 thousandths in vertical play.
 
Driveslayer45 said:
I align the vise with a dial indicator, or test indicator, hanging from the quill with a mag base or quill clamp. then i index off of a tall parallel clamped into the jaws, running the table back and forth and tapping the vise base with a hammer. i shoot for half thou over the 6 inch parallel. The vise came on a swivel base which I've pulled off so get a better mounting to my table. figure one less item to throw off my work.i have not tested it with the swivel base installed.

<-- can you recommend a stone. currently i use an old sharpening stone but its not precision in any way so i rub it very very lightly.

you know i hadn't considered that thinking the machine would be able to handle it but yes, the left is the low side and the vise is centered over the left 1/3rd of the table.
Click to expand...

Your squaring method is fine. My vice did not have keys so I added them. I can put the vise up there bump it and tighten it down and it is within a half thow over 6 inches every time.

Ideally you want a Precision Ground Flat stone. At minimum you want a new stone so it is fairly flat and in a very fine grit. You are not looking to remove material from the whole surface, just the high spots.

I am guessing that you have a fairly small machine, It is surprising how much even something that looks as stout as the table can move, especially if the gibs are a bit loose..
 
I do have a small bench mill, pm-727.

I didn't get a chance to work on it last night, it might be the weekend before I can spend any serious time with it.

Thanks for everyone's help.
 
Just shine your bright hot light on the other side of your vise and you will be good to go...
 
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