To do or not to do, can it be done? MK4 drill steel.

[routercnc]

Depending on the accuracy you need to hold over time if you swap out a spindle then it might not go back in fully trammed. Maybe you can provide some kind of alignment pins or something, but it needs some thought.

Therefore another option is to have 2 spindles - have the low speed spindle in the main housing. Then on the lowest part of the Z axis have a thick plate hanging out the front with the high speed spindle in. This is cantilevered out, which is not so good, but might be good enough for the high speed lighter work. Some Bridgeport owners do this to give both options. Like this but hanging out the front ahead of the gantry beam:



If you want all steel construction have a look at the Mori Seki 5000 for ideas: