Surplus DC motors

Has anyone used those surplus DC motors and controllers I keep seeing
ads for in Home Shop Machinist? I think they were originally used in
treadmills.

I was thinking that they might be just the ticket for a spindle motor
on a small (Sherline size) CNC setup. Do you think there's any
potential there or is there something I don't know that makes it a
non-starter?

They're going for $49 plus shipping, so the price is right but is it
up to the task?

Thanks

Gary