On 2/14/2015 9:00 PM, Gunner Asch wrote:
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

http://www.spsspindle.com/sps-spindl...le-rebuilding/

However...keep in mind that if they grind the spindle taper..your tool
may not..not fill the hole..so they will also have to grind the nose
of the spindle and depending on how much metal they removed..they may
have to recut the holes for the alignment blocks. Generally when
regrinding..they will remove between .015-.05...but...shrug

Have you put a tenths indicator on the spindle taper and find out how
much out of alignment is inside the taper? That is #1 task.

Its entirely possible to have poorly ground or worn tool
holders..which will show up as a bad spindle alignment.

So put a tenths indcator on a holder and check at the inside of the
beginning of the taper..then stick it inside with the longest probe
you have and measure as far inside as you can.

This of course assumes there are ZERO high spots inside the spindle
nose. If there are high spots..they have to go away..hence a Dremel
tool etc etc will knock off high spots/burrs/damage. Better to have a
groove than a ridge.

Gunner

It might be as simple as oil. Or as I found in Dad's lathe when I got it,
the chuck was running a bit off - and there was a chunk of swarf from
inside of the chuck - in the chuck threads. It was pressed on like
everything. The chuck wasn't sitting square. I was able to clean the
thread and clean the chuck for other junk. The chuck screwed onto
the spindle as it should and mounded square on it. The chuck was
back to the normal quality. It had baffled dad, but I think his
eyesight was going badly by then and he missed the smear of steel.

Martin