[davidmb]

HI, I'm looking at making a spindle with a draw bar and taper so that I can make my own tooling that I can change tools quickly, even upgrade to a tool changer later if I can summon up the courage, the question is what angle does a taper have to be to be self releasing I'm familiar with morse tapers but am all too aware of them sticking for a tool changer I guess that the angle needs to be steeper to facilitate easy removal, any idea's?

[HuFlungDung]

Machinery's Handbook contains information on the subject of milling machine tapers in the form of dimensioned drawings and charts. You might as well go with the published standards, commonly known as ISO 30 taper, ISO 40 etc. These are similar to NMTB 30, NMTB 40, etc, except that the NMTB is the older style with extended cylindrical boss which contains the drawbar threads. The ISO series uses pullstuds, so the shanks do not have the extension boss.

Going from memory, I believe the taper on these is something like 3.5 inches per foot. But you would also need to know the drive key dimensions that have been adopted for a given size. Machinery's Handbook is the place to look.

[Geof]

I assume you do not want to go to a Cat 40 that is used in full scale commercial CNC because you have size limitation? What you could do is investigate the smaller tapers that are used on some of the woodworking machines. I have seen ER collet tooling for a Biesse machine that was like miniature Cat40. The advantage to using something standard is your can buy the toolholders if you want to and are not tied into having to make your own forever.

[davidmb]

Thanks for the replies, I was thinking of making the spindle and one tool holder and then getting a local firm to knock out say 20 tool holders to match.

I'm thinking of a toolholder of about 30mm dia at the fat end to take say a 1/4" tool shank. Maybe even shrink fit the tool bits to the holder ( depends how much they cost ).