"Pete C." fired this volley in news:4dfa2a54$0 $15640$ snipped-for-privacy@unlimited.usenetmonster.com:
I think that could introduce some errors beyond that.
Unless you're _positive_, Ig, that the plate itself has been ground flat to within tenths, end-to-end, you have no way of telling if one end is high, or there are bellies or waves in it.
You need to tram to the surface of the bed, which at least once was ground to precision.
LLoyd
Ignoramus30422 fired this volley in news:2oidnZgpw7N3rWfQnZ2dnUVZ snipped-for-privacy@giganews.com:
No, Ig. Not to start. You make both indicators read the _same_spot_ on the bed, and zero them both to that one spot. THEN you start looking for differences, but not until you've zeroed both indicators.
LLoyd
Well, if the ways have wear, this is the only way to establish the true "plane" of motion. Of course, it isn't actually a plane, but a surface that is close to a plane.
If the object you are tramming to is truly planar, you should be able to do better. But, if it is rocking on burrs on the table or not truly flat, then it will be impossible to tram to it with any greater accuracy than the flatness of it.
I can't get better than .001", maybe even worse, but when sweeping the circle, then the deviation of the ways becomes quite clear. I set it so that the +X and -X are equal, and the +Y and -Y are equal. But, there are significant swings of the indicator, for instance from +X around to
-X, there is a rise in the middle, because the table moves in a slight arc from one end to the other.
it won't get any better until I tear the machine down and scrape the ways.
Jon
I think that I am fine the way I am. I just milled an aluminum flat with a 1/2" end mill, and can't feel any surface imperfections.
iGunner Asch on Thu, 16 Jun 2011 18:55:37 -0700 typed in rec.crafts.metalworking the following:
You don't think it better than using Kurt's face as a vice? [s/fx: rimshot!]
pyotr
I'll just go quietly ....
Completely useless. There is no reason the top of the movable vise will be really parallel to anything in particular. Since it is a Kurt, it won't be real far off, but a few burrs on the table or bottom of the vise, on the bed of the vise, under the movable jaw, etc. will add up to it not being real parallel at all. Just put the dial indicator on the top of the vise and run the table around to see how far off it is.
Jion
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