How hard to make a custom cnc spindle?

[rlevin]

To solve the problem of an old, but servicable, cnc mill with an old spindle taper, how hard would it be to make a custom replacement spindle with a modern and more common taper? I am sure it would not be cheap, but we are all parts makers here, and it seems like we should be able to do this, right? What is your opinion?

[andy55]

take a look at:
Milling spindle collaboration project