How tight??

[retailer]

My mill has a 3MT taper for the tooling, rather than a draw bar it has a 70mm diam knurled nut on the spindle nose to retain the tooling. When I first purchased the mill I had no tooling, good friend of mine a toolmaker offered to give me a few pieces to get me going, he watched as I worked - I reached for a set of multigrips to tighten the knurled nut - he stopped me and pointed to the knurls on the nut and said that is for your hand not for multigrips. I only ever tighten by hand and have never had any tooling slip or spin.
I did experience some slip in the lathe though, the tailstock quill has no recess for a tang, so the taper must be in good condition, after the first experince of slip in the lathe I lapped the quill spindle with fine grinding paste and an arbour - not much only took a minute or so, since then (15yrs ago) I have not experienced any slipping even with my largest drill bit a 2MT 1".

 

[OrangeAlpine]

Sure, tighten just enough that it does not spin. Duh!

Try this approach. Each time, tighten the drawbar to the max that will allow reasonable force to remove the tool. I suggest experimenting, using a click torque wrench and establish just what that number might be. Start low and work up to the comfortable maximum. In use, you will probably have to use the torque wrench each time you tighten a tool in place. A small price to pay.

Bill