[Adalovelace]

Someone help me with a mystery. Does anyone have experience with the presence of chatter where it previously did not exist? We're using an HMC 500 OKK. It performs pretty powerful jobs. One of the 37 tools during the cycle roughs out about 0.08" of an inside diameter. It does not interpolate, but basically plunge mills 7" deep. This chatter did not exist until recently after a slew of pressure issues related to the hydraulic clamps on the workpiece fixture. I cannot, for the life of me, get this chatter to fully disappear now. The clamping issues have been resolved, but the chatter remains. Is it possible the spindle has been damaged through repeated running with this chatter? Also, how would I diagnose an issue related to the spindle.

Things I've tried:

Changing speed
Changing feed
Honing the inserts on the boring bar

[Jim Dawson]

A list of other possibilities in no particular order

Insert radius
Insert mounting surface not flat
Feed speed too slow
Something lose in the boring head
Damaged tool holder
Worn pull stud (if equipped)
Damaged spindle tool holder lock
Worn spindle bore
Spindle bearings

[Adalovelace]

Thank you, Jim. I also thought there was a possibility of worn spindle bearings. How would one go about detecting worn bearings?

[Jim Dawson]

After warming the machine up to normal operating temperature, I guess I would use a dial indicator placed on the spindle nose with the indicator base on the quill and pry the spindle radially to see how much play there is. Do this in two planes and in both directions. I'm not sure what the maximum limit would be, but ideal would be 0 indicated movement. There may be a specification and a testing method in the maintenance manual for the machine.

Unless you are getting chatter in other operations, I would be taking a very close look at the tool holder and tooling before going too far with the spindle.