M-head spindle taper mods?

[amuller]

People often ask if these can be bored for R-8 tooling. There is obviously not room for that. But has anyone investigated reworking one of these for ER tooling? Rather casual measuring suggests that the spindle could be bored and threaded for ER25 collets and retaining nuts. This could have some advantages including: (1) tooling current and readily available from many sources, (2) No need for a drawbar and pounding on same, as ER tooling is released from the business end, and (3) takes shanks up to 5/8" as opposed to 1/2".

But there might very well be good reasons why this is not a good idea. Just asking....

Alan

 

[seanb]

Wish I knew a place that could regrind the spindle to even MT2.
B&S No.7 is obsolete and import stuff available is garbage.

Whats the diameter of an ER25 collet? I have got some ER32 and they are too big for the spindle. The big end of a B&S no.7 measures .725

 

[Holescreek]

Back when I had an M-head I just bought MT3 tapered or straight shanked stuff and ground the shanks to B&S #7 for it.