DC Motor types

Hi all,

I have a load of Field wound DC motors. Are these any good for CNC
work (I have a pallet load of them). I tried one this evening hooked
up to a Gecko Drive it seemed to work ok, but was lacking in power I
think.
I have hooked it up through a bridge rectifer, with both fields
hooked up in series going to the DC pos and neg, and then one of the
armature windings going to one AC leg, the other armature going
direct to power source and lastly the other power source going to the
remaining AC leg.
This makes the motor turn in both direction OK but is it good enough
for CNC?????

Regards
Andrew