Machining A Vise Square

[hman]

3dshooter80 - You said, "I proceeded to flip the vise over on its ways, clamp it down lightly, just enough to hold it, and milled the bottom." I have the feeling the clamping itself might have caused some warpage.

Perhaps you could machine a "known square" block of steel, a little bit taller than the depth of the vise jaws, a couple inches wide (so it will span at least two of the T-slots on your mill table) and at least as long as the jaws. If possible, you could even have it surface ground. Secure the block to the mill, then invert the vise over the block and tighten it. This should guarantee that the vise ways are parallel to the table under "in use" conditions. Then do a careful job of milling the vise base surface.

 

[John Hasler]

Are you certain that your mill table is not only trammed, but flat?

 

[Andre]

Very true Andre! You are much better off taking narrow passes with an end mill. Both the end mill and fly cutter will leave there own undesirable finish. But when using an end mill the project should have a flatter overall in plane result. A surface grinder or Blanchard grinder would be nice to have right about now…Dave

Eh, id rather have a milled surface on the bottom of my vise. More grip! Especially when there's oil in the equation. Imagine driving on drag radials in the winter.

If you do want it smooth however, you can use an oil stone. Once the milling marks are gone in one spot move on to the next area, all the milling marks should be basically the same depth so use the scratch marks as a stoning guide. I've had good luck doing that, and it should be just about as flat after stoning.

 

[Andre]

3dshooter80 - You said, "I proceeded to flip the vise over on its ways, clamp it down lightly, just enough to hold it, and milled the bottom." I have the feeling the clamping itself might have caused some warpage.

Perhaps you could machine a "known square" block of steel, a little bit taller than the depth of the vise jaws, a couple inches wide (so it will span at least two of the T-slots on your mill table) and at least as long as the jaws. If possible, you could even have it surface ground. Secure the block to the mill, then invert the vise over the block and tighten it. This should guarantee that the vise ways are parallel to the table under "in use" conditions. Then do a careful job of milling the vise base surface.

That's probably where the warpage is coming from.

When clamped, you have tension on one side not the other, so the non tensioned side till bow hollow in the center. When the vise is clamped down to the mill table, with bolts in the CENTER of the vise, the clamping bolts prevent it from bowing and hold it flat to the table.

Maybe I'm overthinking things, because if you have a swivel vise it's not directly held down.

 

[RJSakowski]

If you have a 2-4-6 block, you could mount it on the table and use that as mount for the inverted vise. That way, the floor of the vise is parallel with the table and the 4 x 6" provides enough distance to minimize any error in mounting. Make sure that you tap it in after closing the jaws in case the vise rides up when tightening.

Bob

 

[mws]

I have the feeling the clamping itself might have caused some warpage.

Perhaps you could machine a "known square" block of steel, a little bit taller than the depth of the vise jaws, a couple inches wide (so it will span at least two of the T-slots on your mill table) and at least as long as the jaws. If possible, you could even have it surface ground. Secure the block to the mill, then invert the vise over the block and tighten it. This should guarantee that the vise ways are parallel to the table under "in use" conditions. Then do a careful job of milling the vise base surface.

John, you beat me to it. I agree with hman. I have trued up quite a number of less than precise tooling. I believe they call it "Turd Polishing". For any work holding device I first indicate on a surface plate for any way out surfaces. Barring anything too far off I do like John said, bite a good piece of stock in the jaws and clamp that to the table. That fixes the two way surfaces nearest the fixed jaw true to the mill table. I then use a machinist jack, or shims, to support the other end under the screw and clamp that as best as possible so as NOT to take out any twist in the frame. I then very lightly fly cut the bottom, a few times, until it "feels right". I then flip it over and go from there as the DI directs.

For angle vises I replace the pivot shaft with a longer one and clamp that in V-blocks to the table. EVERYTHING must then be milled true to that shaft's axis. A little more touchy but again, the three point clamping to start off works best for me. Even with the pivot as the clamped reference I still bite something in the jaws to stress the vice frame.

 

[LEEQ]

Nobody has mentioned that after milling and until stress relieving, cast iron will move. Sometimes right off, sometimes down the road. Actions such as single point planning, scraping, surface grinding don't impart the stresses to the iron like milling. As it stands, until you heat treat it, you're not dealing with a stable piece. You could chase the movement forever, or make it all good only to find it changes later. One of the Moore books, Foundations of Mechanical Accuracy, describes all this in straight forward, understandable terms. Best of Luck.

 

[lpeedin]

I think I am just going to buy a better vise.

 

[LEEQ]

I'm right there with you. In the mean time my enco will have to suffice. I love learning about this stuff, but I hate buying the stuff I think I can afford. It all seems to be in kit form. When I win the lottery, I can buy nice tools. Then maybe work on something other than tools.

 

[skipmeister]

You may want to check with the local automotive machine shops. Most used to have wide surface grinders for flywheels resurfacing.