This is my 1st post so please be patient :) I am having flatness issues. I have 6" diameter stainless steel blank discs. They are about .25" thick. My finish thickness is .19". So that leaves me about .03" per side to face off. I have to maintain .0005" flatness and a 32 finish. I made a fixture plate to bolt them on to and the part is flat until I unbolt the part (bolts are screwed in from the back side of the fixture plate). I even tried to torque the part down but no luck. I also tried some aluminum pie jaws with the chuck pressure turned down pretty low (100 psi). I think any lower the part might fly out. I am having the same issue with the pie jaws. I'm using a test indicator and I zeroed it out on the edge(0 degree side) and ran it from the edge to the center of the part it went from 0 to -.002 then I ran it from the center to the opposite side(180 degree side) and it went from -.002 to 0. Then when I measure the 90 degrees to 270 degree side I'll get something like .002 on the outside to -.002 in the center to .004 in the opposite side. So I know when if bolt or chuck on the part it distorts the part.
I could get them lapped but I have to keep the cost down! Any tips or ideas would be much appreciated.
I could get them lapped but I have to keep the cost down! Any tips or ideas would be much appreciated.