I often see the G74 and G75 commands explained together for CNC lathes, but as far as I know, these two commands are different. Also, CYCLE is already used in Siemens control. Can you explain what these two commands do on a CNC lathe and their formats?

G74 and G75 are canned cycles used in CNC lathes to ensure chip control and reduce the risk of tool breakage [1]. These cycles aim to break down chips into small pieces for safe evacuation [1].

G74 (Face End Grooving / Face Peck Drilling): This cycle is typically used for drilling or cutting narrow grooves on the face of the workpiece. The operation proceeds along the Z-axis, with intermittent retracts to break or evacuate chips [1].

• Command Structure:
  • First Block: Defines the safe retract (clearance) distance. This value is valid as long as the cycle is active [1].
  • Second Block: Defines the target endpoint coordinates (Z-axis), peck depth increments (P), and retract amount (Q) [1].

G75 (OD/ID Radial Grooving): This cycle is used for cutting radial grooves on the outer or inner diameter. The operation proceeds along the X-axis, with short incremental moves and retracts to facilitate chip evacuation [1].

• Command Structure:
  • First Block: Defines the safe retract (clearance) distance. This value is valid as long as the cycle is active [1].
  • Second Block: Defines the target endpoint coordinates (X-axis), peck depth increments (P), and retract amount (Q) [1].

General Considerations:

• Spindle rotation must be active when using these cycles [1].
• Tool nose radius compensation (G40) should be canceled before calling the cycles [1].
• On Siemens controllers, it may be necessary to activate the ISO converter by explicitly programming the G291 code [1].
• Cutting depth values (P and Q) should be programmed as positive incremental values [1].