Setting Up Rotary Table angle with 2 different Diameters

[[Is...]]

I have a part with the bearing diameters being 2 different sizes and on opposite ends of the part (approx 20 inches), am I able to use both of those diameters in cylinders into a 3d line and then "symmetry" of that 3d line to establish rotary lean? The closest I can get is just 1 diameter (approx 2.5 inches in length) to scan the 180 deg and pull that into my symmetry needed for the rotary table axis. A half circle scan at each end with a 3d line between them establish my rotation in space, X0,Y0. I am seeing about 4x higher runout on the cmm than what I see between centers. I have swept the centers with an indicator / probe and checked runout to the bores they are good. 

 

Any ideas or best practice? Today was day 1 with the rotary so any suggestions / ideas are appreciated!

[[Cl...]]

Are you trying to create a rotary alignment to help remove runout in the part? We do this by measuring the first

cylinder at 0° and again at 180°. Then create a symmetry from the two. Using that for the rotary alignment.

[[Is...]]

Yes, so I got it work by establishing cylinders on each end and at 0/180 like you stated. Runout still seems high, but my loop will not run. I have it set to [1,3,1]. Basing off an old program and I see no difference.

[[Cl...]]

Have you checked the runout of the part using a different method to see if it correlates to the rotary?

Like maybe putting Saint Mary's gage and checking runout with a test indicator?

Edited October 3, 2025

[[Is...]]

Yessir, between centers I am within .0006 TIR at 4 different locations. CMM is showing .0022.

[[Cl...]]

I'd double check your rotary set-up/alignment, etc. Something doesn't add up.

[[Cl...]]

Holding and checking in the exact same spot as the CMM?

[[Is...]]

Yep, I have the locations marked so im within .050 of those locations. CMM is just chucked to the btm diameter, I can see that I am off a couple degrees relative to the CMM but according to my base alignment I am corrected to account for that. I agree that I am missing something in my rotary set up but I cant figure it out. 

[[Cl...]]

You are tactile probing/scanning this part?

I'd start by checking into the stylus for any abnormalities there.

Edited October 3, 2025