Common G-Codes for CNC Programming

G00	Rapid positioning	On 2- or 3-axis moves, G00 (unlike G01) traditionally does not necessarily move in a single straight line between start point and end point. It moves each axis at its max speed until its vector is achieved. Shorter vector usually finishes first (given similar axis speeds). This matters because it may yield a dog-leg or hockey-stick motion, which the programmer needs to consider depending on what obstacles are nearby, to avoid a crash. Some machines offer interpolated rapids as a feature for ease of programming (safe to assume a straight line).
G01	Linear interpolation	The most common workhorse code for feeding during a cut. The program specs the start and end points, and the control automatically calculates (interpolates) the intermediate points to pass through that will yield a straight line (hence "linear"). The control then calculates the angular velocities at which to turn the axis leadscrews. The computer performs thousands of calculations per second. Actual machining takes place with given feed on linear path.
G02	Circular interpolation, clockwise	Cannot start G41 or G42 in G02 or G03 modes. Must already be compensated in earlier G01 block.
G03	Circular interpolation, counterclockwise	Cannot start G41 or G42 in G02 or G03 modes. Must already be compensated in earlier G01 block.
G04	Dwell	Takes an address for dwell period (may be X, U, or P)
G05 P10000	High-precision contour control (HPCC)	Uses a deep look-ahead buffer and simulation processing to provide better axis movement acceleration and deceleration during contour milling
G05.1 Q1.	Ai Nano contour control	Uses a deep look-ahead buffer and simulation processing to provide better axis movement acceleration and deceleration during contour milling
G07	Imaginary axis designation
G09	Exact stop check
G10	Programmable data input
G11	Data write cancel
G12	Full-circle interpolation, clockwise	Fixed cycle for ease of programming 360° circular interpolation with blend-radius lead-in and lead-out. Not standard on Fanuc controls.
G13	Full-circle interpolation, counterclockwise	Fixed cycle for ease of programming 360° circular interpolation with blend-radius lead-in and lead-out. Not standard on Fanuc controls.
G17	XY plane selection
G18	ZX plane selection	On most CNC lathes (built 1960s to 2000s), ZX is the only available plane, so no G17 to G19 codes are used. This is now changing as the era begins in which live tooling, multitask/multifunction, and mill-turn/turn-mill gradually become the "new normal". But the simpler, traditional form factor will probably not disappear—just move over to make room for the newer configurations. See also V address.
G19	YZ plane selection
G20	Programming in inches	Somewhat uncommon except in USA and (to lesser extent) Canada and UK. However, in the global marketplace, competence with both G20 and G21 always stands some chance of being necessary at any time. The usual minimum increment in G20 is one ten-thousandth of an inch (0.0001"), which is a larger distance than the usual minimum increment in G21 (one thousandth of a millimeter, .001 mm, that is, one micrometre). This physical difference sometimes favors G21 programming.
G21	Programming in millimeters (mm)	Prevalent worldwide. However, in the global marketplace, competence with both G20 and G21 always stands some chance of being necessary at any time.
G28	Return to home position (machine zero, aka machine reference point)	Takes X Y Z addresses which define the intermediate point that the tool tip will pass through on its way home to machine zero. They are in terms of part zero (aka program zero), NOT machine zero.
G30	Return to secondary home position (machine zero, aka machine reference point)	Takes a P address specifying which machine zero point is desired, if the machine has several secondary points (P1 to P4). Takes X Y Z addresses which define the intermediate point that the tool tip will pass through on its way home to machine zero. They are in terms of part zero (aka program zero), NOT machine zero.
G31	Skip function (used for probes and tool length measurement systems)
G32	Single-point threading, longhand style (if not using a cycle, e.g., G76)	Similar to G01 linear interpolation, except with automatic spindle synchronization for single-point threading.
G33	Constant-pitch threading
G33	Single-point threading, longhand style (if not using a cycle, e.g., G76)	Some lathe controls assign this mode to G33 rather than G32.
G34	Variable-pitch threading
G40	Tool radius compensation off	Cancels G41 or G42.
G41	Tool radius compensation left	Milling: Given righthand-helix cutter and M03 spindle direction, G41 corresponds to climb milling (down milling). Takes an address (D or H) that calls an offset register value for radius.
G42	Tool radius compensation right	Similar corollary info as for G41. Given righthand-helix cutter and M03 spindle direction, G42 corresponds to conventional milling (up milling).
G43	Tool height offset compensation negative	Takes an address, usually H, to call the tool length offset register value. The value is negative because it will be added to the gauge line position. G43 is the commonly used version (vs G44).
G44	Tool height offset compensation positive	Takes an address, usually H, to call the tool length offset register value. The value is positive because it will be subtracted from the gauge line position. G44 is the seldom-used version (vs G43).
G45	Axis offset single increase
G46	Axis offset single decrease
G47	Axis offset double increase
G48	Axis offset double decrease
G49	Tool length offset compensation cancel	Cancels G43 or G44.
G50	Define the maximum spindle speed	Takes an S address integer which is interpreted as rpm. Without this feature, G96 mode (CSS) would rev the spindle to "wide open throttle" when closely approaching the axis of rotation.
G50	Scaling function cancel
G50	Position register (programming of vector from part zero to tool tip)	Position register is one of the original methods to relate the part (program) coordinate system to the tool position, which indirectly relates it to the machine coordinate system, the only position the control really "knows". Not commonly programmed anymore because G54 to G59 (WCSs) are a better, newer method. Called via G50 for turning, G92 for milling. Those G addresses also have alternate meanings (which see). Position register can still be useful for datum shift programming.
G52	Local coordinate system (LCS)	Temporarily shifts program zero to a new location. This simplifies programming in some cases.
G53	Machine coordinate system	Takes absolute coordinates (X,Y,Z,A,B,C) with reference to machine zero rather than program zero. Can be helpful for tool changes. Nonmodal and absolute only. Subsequent blocks are interpreted as "back to G54" even if it is not explicitly programmed.
G54 to G59	Work coordinate systems (WCSs)	Have largely replaced position register (G50 and G92). Each tuple of axis offsets relates program zero directly to machine zero. Standard is 6 tuples (G54 to G59), with optional extensibility to 48 more via G54.1 P1 to P48.
G54.1 P1 to P48	Extended work coordinate systems	Up to 48 more WCSs besides the 6 provided as standard by G54 to G59. Note floating-point extension of G-code data type (formerly all integers). Other examples have also evolved (e.g., G84.2). Modern controls have the hardware to handle it.
G70	Fixed cycle, multiple repetitive cycle, for finishing (including contours)
G71	Fixed cycle, multiple repetitive cycle, for roughing (Z-axis emphasis)
G72	Fixed cycle, multiple repetitive cycle, for roughing (X-axis emphasis)
G73	Fixed cycle, multiple repetitive cycle, for roughing, with pattern repetition
G73	Peck drilling cycle for milling - high-speed (NO full retraction from pecks)	Retracts only as far as a clearance increment (system parameter). For when chipbreaking is the main concern, but chip clogging of flutes is not.
G74	Peck drilling cycle for turning
G74	Tapping cycle for milling, lefthand thread, M04 spindle direction
G75	Peck grooving cycle for turning
G76	Fine boring cycle for milling
G76	Threading cycle for turning, multiple repetitive cycle
G80	Cancel canned cycle	Milling: Cancels all cycles such as G73, G83, G88, etc. Z-axis returns either to Z-initial level or R-level, as programmed (G98 or G99, respectively).
G81	Simple drilling cycle	No dwell built in
G82	Drilling cycle with dwell	Dwells at hole bottom (Z-depth) for the number of milliseconds specified by the P address. Good for when hole bottom finish matters.
G83	Peck drilling cycle (full retraction from pecks)	Returns to R-level after each peck. Good for clearing flutes of chips.
G84	Tapping cycle, righthand thread, M03 spindle direction
G84.2	Tapping cycle, righthand thread, M03 spindle direction, rigid toolholder
G90	Absolute programming	Positioning defined with reference to part zero.
G90	Fixed cycle, simple cycle, for roughing (Z-axis emphasis)	When not serving for absolute programming (above)
G91	Incremental programming	Positioning defined with reference to previous position.
G92	Position register (programming of vector from part zero to tool tip)	Same corollary info as at G50 position register.
G92	Threading cycle, simple cycle
G94	Feedrate per minute	On group type A lathes, feedrate per minute is G98.
G94	Fixed cycle, simple cycle, for roughing (X-axis emphasis)	When not serving for feedrate per minute (above)
G95	Feedrate per revolution	On group type A lathes, feedrate per revolution is G99.
G96	Constant surface speed (CSS)	Varies spindle speed automatically to achieve a constant surface speed. See speeds and feeds. Takes an S address integer, which is interpreted as sfm in G20 mode or as m/min in G21 mode.
G97	Constant spindle speed	Takes an S address integer, which is interpreted as rev/min (rpm). The default speed mode per system parameter if no mode is programmed.
G98	Return to initial Z level in canned cycle
G98	Feedrate per minute (group type A)	Feedrate per minute is G94 on group type B.
G99	Return to R level in canned cycle
G99	Feedrate per revolution (group type A)	Feedrate per revolution is G95 on group type B.