i also have a denford triac with the standard sem servo motor, owned the machine for 3 years. ive never once managed to stall the spindle.

i do 1mm deep cuts in ally with a 20mm end mill no problem, i also do 2mm deep cuts with an 8mm end mill no problem. the motor has plenty of torque.

but i do agree it is pretty slow on the rpm front and i have also been looking at other options for new motors. although i can take 2mm of ally off at once with a good finish, due to the low rpm feed rate is pretty slow at about 250mm/m.

the current sem servo motor in the traic is £1200 new and brand new replacement with more speed is going to cost even more. the thing to bare in mind when looking at the high speed chinese spindles is the atc and bt35 tool holders are only rate to about 8-10k rpm.