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G73

Machining center, LatheModal, group 09

High-speed peck drilling cycle (chip breaking, small retract)

⌨On machining centers

G73 X_ Y_ Z_ R_ Q_ (depth of cut per pass) F_ K_ (repeat count)

Retracts a small amount (set by parameter) every Q to break chips. Does not retract out of the hole
Q is an unsigned incremental value
Chip evacuation is weaker than G83. For deep holes or materials that pack chips, use G83

Diagram: G73 motion (side view)

Cuts in by Q each time, retracting a little (d, a machine setting) each time to break the chips. It doesn't retract out of the hole, so it is fast, but chip evacuation is weaker than G83. Figure shows G98.

◎On lathes: Pattern repeating (closed-loop cutting) cycle (cuts following the stock shape, e.g. castings)

The same number means something different on lathes (FANUC-type G-code system A). Group 00.

G73 U_ (total X relief) W_ (total Z relief) R_ (number of divisions);
G73 P_ Q_ U_ W_ F_ S_ T_

For stock that has an allowance following the finished profile, such as forgings and castings
Finish with G70

Diagram (lathe): how G73 (lathe) cuts

Traces the finished shape offset from the part, reducing the offset each pass for the specified number of passes. For castings and forgings where the stock follows the contour. Finish with G70.

≠Differences between controls and machines

The same code can be written or assigned differently depending on the CNC control and the machine builder. Always check your machine’s manual.

Source	Machine	Item	Detail
Haas	Machining center	Format	Can also be specified with I (first depth of cut), J (reduction per pass), K (minimum depth of cut)Haas has three ways: Q only, I/J/K, or K and Q. The retract amount is Setting 22
NIST	Machining center	existence	Not defined
Haas	Lathe	Format	G73 P_ Q_ D_ (number of passes) I_ K_ U_ W_ F_ S_ T_ (one-block format)On Haas, D is the number of passes and I/K are the total relief from first to last pass

📚Sources

The meaning shown agrees in at least two sources (agreement confirmed). Explanations are written in our own words.

Siemens AG — SINUMERIK 802D sl/840D/840D sl/840Di/840Di sl/810D Programming Manual ISO Milling, 04.2007 Edition (6FC5398-7BP10-0BA0) cache.industry.siemens.com
Haas Automation, Inc. — G-code, M-code, and Setting (per-code explanation pages) haascnc.com
Haas Automation, Inc. — Mill Operator's Manual – 17 Mill G-Codes (online version) haascnc.com
National Institute of Standards and Technology (NIST), USA — The NIST RS274NGC Interpreter – Version 3 (NISTIR 6556, 2000) nvlpubs.nist.gov
Siemens AG — SINUMERIK 802D sl/840D/840D sl/840Di/840Di sl/810D Programming Manual ISO Turning, 04.2007 Edition cache.industry.siemens.com
Haas Automation, Inc. — Lathe Operator's Manual – 16 Lathe G-Codes (online version) haascnc.com