On Fri, 13 Feb 2015 18:09:02 -0600, Karl Townsend
wrote:

I have a runnout problem in the spindle on my CNC mill. means small
tooling, like endmills under 1/8" diameter break constantly. Driving
me nuts again this week.

Last year, I took the spindle apart and installed all new bearings -
no help.

I had read that the entire spindle cartridge could be sent in and have
the 40 taper reground to be exactly true. Not sure where a place like
this might be.

Any suggestions on my next step here?

Karl
Greetings Karl,
Some of the tool holders I have run out too much for small cutters.
Really, a 1/8 cutter should run true within a tenth, and a few of my
holders for small tools run out about 3 tenths. I made an eccentric
bushing for a small cutter but I don't like holding cutters in
bushings that slip in. So I am considering putting the tool holders in
the machine and boring them large enough to take a pressed in bushing.
Then boring to bushing in the holder in the spindle. Since all my
holders ALWAYS go in the same way the holder should always run true.
Eric