Hi, picked up this mill head/spindle at auction today. This was removed from a working Bostomatic MM304 mill. I did not get any tool holders for it and was wondering if any body had any info on toolholders. It appears to be a standard 40 taper. I was told by a guy at the auction that the taper is possibly unique to the Bostomatic and that a standard toolholder would not work. I would like to use this head on my DIY CNC Mill project that I am covering in the project threads. Thanks to all in the community for making this a great site.

BigBam

NMTB 40 milling machine taper was one available from BD Also 300 Universal Kwik-Switch Good piece of equipment.

What you have is the same as on my bostomatic 312 mill. Most of the holders specifically for this machine were made by Universal Engineering. It is a standard 40 taper. The tool taper portion of an NMTB40, a CAT 40 and a BT 40 are all the same. The holders that fit my machine have to also fit the tool changer so this will not be an issue with you unless you plan on incorporating a tool changer system. You can use a cat 40 taper with the proper pull stud and it will work just fine in the larger taper. I am sure you realize there are 2 spindles and the other spindle is much smaller high speed type spindle. I am not sure on it but I believe it is something like an ISO 20 taper. Do a google search on Bostomatic 300 series mills and you will learn a lot more. This guy on ebay has the appropriate holder and pull studs for your spindle I believe. I bought 20 holders from him and he apparently still has some left.
http://cgi.ebay.com/Cat-40-Bostomatic-Acura-Flex-Jacobs-adapters_W0QQitemZ330036508457QQihZ014QQcategoryZ45018QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
It appears the pullstuds are not on these holders, but you can email him and see if he has any remaining. If not look up bostomatic on ebay and there are other collet chucks that include the pull stud. I hope this helps if I can help you any more please ask.
-Greg Beaman