Machine vice Groz 4" needs truing

[Anzaniste]

My 4" Groz Machine vice is not parallel to its base. I had tramming in the milling machine table and squared up the ends of some flat stock which was resting on the bottom of the vice opening. When I took the job out of the vice the ends were ever-so slightly not square. On checking the tram of the bottom of the vice jaws by putting a 6 inch length of flat stock in  they were about 10thou in 5 inches out of whack.

My plan is to true the base to the bottom of the vice jaws by pulling down onto a couple of 123 blocks on the face plate of the lathe and skimming the minimum amount off.

Are there any potential problems that I may not have foreseen in my proposed method?

This is a picture of the vice for those not familiar.

 

[cidrontmg]

That's a good plan. Some years ago I bought a 80 mm Soba (or Glanze, but Indian anyway) mill vice, came from India, then UK, to Portugal. Probably their vice jaws were originally parallel and square, but no wonder that all "journeyism" made their vice jaws a bit wonky.
So vice jaws screwed off, there were somewhat hardened grease and gunk, I cleaned minutely everything, also the base, and milled just a whiff to ensure that the bases are flat and square. Screwed and tightened again, running with a DIY, their "new" jaws are exact parallel and square. Quite nice. 

[tekfab]

Why aren't you just clamping it on your mill table and machining it there ?  It would be "true" to the machine you are actually using it on.

Mike

[Anzaniste]

Two reasons.
1) Lazyness, the lathe has powered cross feed so I can turn it on and watch it do the work.
2) Cosmetics, I do not like to see the broad lines left by each pass of the milling cutter.

I guess that it is also a confidence thing as well. I have much more experience with my lathe.

[tekfab]

LOL ! Yeh, lazyness will do it. It's just that i saw that your machine had horizontal capabilities so i though you'd just bang in a nice cutter and skim the vice to match your machine. (good practice ? )

Mike

[Anzaniste]

Aha, you meant use the horizontal spindle, what a good idea and I do have a suitable cutter. Hey-ho too late I've just come back from my other workshop where I couldn't manage to hold it sensibly on the big lathe so I stuck it on the Bridgeport (with power feeds) and used a fly cutter. Judging by the cutting pattern it was out of whack in both directions. Ithink this might answer one or two other problems I have had in the past.