Quote Originally Posted by Dangle_kt View Post
Well I can't measure run out on the actual end mill, so I am using various parts of the toolholder/spindle housing as proxies....

Is this normal? Or does the tool holder need slinging

https://www.youtube.com/watch?v=g0JeX-duL9A

I see you are measuring the nut. The nut will always be bad. Youtube is having a bad day here so cant watch all.

Measure the runout of the taper in the spindle to establish if it is running true. You should have a total movement of less than 0.01mm (according to my old books)

Then install a tool holder and measure the TAPER of the collet . NOT the thread or the locking nut.

Then install a ER collet with a reference bar. A ground piece of metal like a edgefinder is fine and measure that.

With good stuff you should not have a cumulative runout of more than 0.05mm