Very odd indicator readings

[aaron p]

Ok guys, im still scratching my head with this one, and bear with me, I just got home from a 13hr shift (words may be off). We run round fixtures on the Integrex E-410 5axis at work. (lathe/mill combo). When we indicate the fixture in, it has 2 pins in-line with eachother, or has a round incating ball stud that is also inline. We have to roll the c-axis so that the centerline of the part is correct when we mill the side rails on it. The dowl pins are in the center of the part. The part is called a slip and its made in a ring, then sawed into sections and then we mill the side angled rails on it. Well, anyway. I indicated the dowl pin, teached C zero on G54. Ran one part and somehow the centerline was off. So, I put the ball stud in the fixture, and indicated the ball stud, only .007* in C off, now we put in a co-axial indicator and it showed .039* C off. How the heck can my Brown and Sharpe Best-test indicator with a Indicol Adjustal holder be that much different when indicating the same exact thing? We used a drill chuck in the spindle to hold the co-axial and I clamped on that with my test indicator. Any ideas?

[odind]

If your indicator is @ an angle (not square to the pin) the reading is false. Also try a swiss made indicator.

[Eurisko]

If the spindle isn't perfectly perpendicular to the part, and if there is a difference in the "Z" spindle position (using different indicators) when tramming the pin, that could account for the difference.

Try setting an angle plate on the fixture locating surface, then tram the face of the plate to check for an "out of square" condition.

[aaron p]

Originally Posted by odind If your indicator is @ an angle (not square to the pin) the reading is false. Also try a swiss made indicator.

Brown and Sharpe is swiss made.