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The G73 cycle is intended for deep drilling with chip breaking. The retracts in this cycle break the chip but do not totally retract the drill from the hole. It’s suitable for tools with long flutes which clear the broken chips from the hole.

Program: G73 X~ Z~ R~ L~ Q~

  • Q~ is the delta increment along the Z-axis

The G73 cycle is as follows:

  • Step 1: Preliminary canned cycle motion.
  • Step 2: Move the Z-axis only at the current feed rate downward by delta or to the Z position (whichever is less deep).
  • Step 3: Rapid back incrementally in Z 0.010 in.
  • Step 4: Repeat Step 1 through 3 until the Z position is reached at Step 1.
  • Step 5: Rapid back down to the current hole bottom, backed off a bit.
  • Step 6: Retract the Z-axis at traverse rate to clear Z.


It’s an error if:

  • The Q number is negative or zero
  • The R number is not specified