Hello Ray:
Are you familiar with the "Universal Houdaille Kwik-Switch 200" tool holder, and BP spindle replacement?
I have two of them; one is installed on a manual BP clone, and the other is on a large Lagun mill, 40 taper spindle, with CNC. You can change tools by hand (no wrench required) in about 6 or 8 seconds. The spindle must have a brake, and you can change the tool holder with one hand.
My third mill is a bed-type CNC with a 16 pocket carousel tool changer. The tool holders are BT-40. Back when I bought tooling for that mill, 1990, I was able to get BT-40 tool holders with the Universal Houdaille collet taper bore/lock nut arrangement. This enables me to utilize the same collets and nuts on all three machines.
Of course, you get absolute repeatable Z axis offsets for all your tools.
The tool holders are positive drive with two drive tangs on the body, and they have three style collets.
(1)Acra-flex, which has a small range in tool shank diameter
(2)Acra-mill super high precision, which takes the exact tool diameter without an internal drive plug.
(3)Acra-grip, same style and precision as (2), but has a spring-loaded plug, which drops into the mill cutter flat giving a positive, no-slip drive to the end mill for heavy milling.
The down side to all this is, Universal Houdaille went out of business back in the 80's, due to the insane Wall St. leveraged buy-out swindle (Investment bankers call it good business!).
There are companies making collets and other parts. There are also new and used Universal Houdaille collets and parts on E-bay.
I just looked on E-bay, and they have a good condition BP clone spindle for sale, and loads of collets, and tool holders.
I consider changing over to the Kwik-switch 200 system one of my best investments in tooling.
Regards,
John