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

"At the core of liberalism is the spoiled child,
miserable, as all spoiled children are, unsatisfied,
demanding, ill-disciplined, despotic and useless.
Liberalism is a philosophy of sniveling brats."
PJ O'Rourke