The Virtual Machine Shop

spindle speed limiter

In CNC lathe programming the G50 word can is used to limit spindle speed. Alert! G50 has three meanings! G50 on a CNC mill is for scaling and G50 on a CNC lathe is either for spindle speed limiting or assigning program zero.

A CNC lathe can be programed to maintain constant surface feet per minute (spindle RPM changes as the tool gets closer to the center of the spindle). Therefore a theoretical spindle speed of infinitely high RPM would be required as the tool approached the spindle centerline. The G50 command allows the RPM to ramp up but to, but not past, the programmed G50 RPM. G50 uses the S word to denote the RPM limit.

Example: G50 S2000 limits the RPM of the spindle to 2000 regardless of any other program word or command.