Centec Mill

Sieg SX3


I managed to get hold of a small CNC lathe. Its a Myford Speed 10 that was converted to CNC commercially in the late 80's - lots of them were done as training machines for colleges & schools. The control was via a BBC Master computer.

The only problem with the old controller was - it didn't do internal threads.

for pictures and specifications of the non CNC version.

It has a few nice touches, like thrust races between the stepper motor faces and the rigid ballscrew connector to kill any backlash there, and telescopic shrouds on Z axis ballscrew.

It was originally driven unipolar, I've replaced both steppers with double ended and driven bipolar via Gecko's. There's a Nema 23 240oz in on X and Nema 34 480oz in on Z. They seem plenty meaty enough, It will take 40 thou cuts in steel, but I limit myself to .5mm (20thou) on roughing, tool & machine life is more important to me than speed <G>.

The screw pitches are metric, X is 2.5mm, Z is 4mm, it will run at well over 40 inches per minute on rapids, which on such a small machine is too fast for my liking. I've de-rated it somewhat by limiting top speed to 20 ipm.

The machine runs flawlessly using Dolphin Partmaster as my CAD/CAM program and Mach3 as the controller.

Here are some close up detail pictures for those thinking of converting one of the similar far eastern models.

Note the last picture, Its the spindle speed sensor as shown on my CNC page. It's just a disc with a 2mm slot running in the opto gap. Works fine and contrary to popular belief, it is possible to make multi-start threads with only 1 pulse per rev!!


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Stepper Motor Drives, Stepping Motors and Motion Control Equipment from Alzanti

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Steve Blackmore

Copyright 2003 Steve Blackmore