Machine Code Glossary for Machining Centers

What is G-Code?

G-code is the common name for the most widely used numerical control (NC) programming language. Used primarily in automation, it is part of computer-aided engineering. G-code is also known as “G programming language”.

In basic terms, G-code is a language in which people tell computerized machine tools what to make and how to make it. The "how" is defined by instructions on where to move to (direction of travel), how fast to move (rapid or controlled feedrate) and through what path to move (linear, circular, etc). The most common example is that, within a machine tool, a cutting tool is moved according to these instructions through a toolpath, cutting away excess material to leave only the finished workpiece. The same concept also applies to non-cutting tools, such as forming or burnishing tools and to measuring probes that validate the results. Commonly Used G Codes for Machining Centers

G00 = Linear move (Rapid) G01 = Linear move (Feed) G02 = Circular move (interpolation) CW G03 = Circular move (interpolation) CCW G04 = Dwell time G10 = Zero offset shift G11 = Zero offset shift (cancel) G17 = XY plane selection G18 = ZX plane selection G19 = YZ plane selection G20 = Check for Inch mode G21 = Check for MM mode G28 = Return to reference point G29 = Return from reference point G30 = Return to 2nd, 3rd (etc.) reference point G40 = Cutter (diameter or radius) compensation off G41 = Cutter (diameter or radius) compensation to the left of the programmed path (climb) G42 = Cutter (diameter or radius) compensation to the right of the programmed path (conventional) G43 = Tool length compensation with spindle approach from positive (+) side G44 = Tool length compensation with spindle approach from negative (-) side G45 = Increase end position by tool offset value (single expansion) G46 = Decrease end position by tool offset value (single reduction) G47 = Increase end position by twice the offset value (double expansion) G48 = Decrease end position by twice the offset value (double reduction)

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G49 = Tool length compensation cancel G53 = Coordinate system referenced from machine home G54 = Work coordinate shift (Fixture Offset #1) G55 thru G59 = Work coordinate shift (Fixture offsets #2 thru #6) G81 = Basic drilling cycle. Feed in, rapid out. G82 = Counterbore cycle. Feed in, dwell, rapid out. G83 = Peck drilling cycle. Feed in peck amount, rapid out, rapid in within .050 of last peck and repeat until depth is reached. G84 = Tapping cycle. Feed in, spindle stop, reverse, feed out. Note: This cycle will vary depending on the Manufacturer of Machining Center. G85 = Boring cycle. Feed in, feed out. G86 = Boring cycle. Feed in, dwell, feed out. G87 = Boring cycle. Feed in, dwell, spindle stop, rapid out. G88 = Boring cycle. Feed in, dwell, spindle stop, move insert away from wall, rapid out. G89 = Boring cycle. Rapid in, dwell, start spindle, feed up, dwell, rapid down, dwell. Also known as the following: reverse counter boring, back facing or back boring cycle. G90 = Absolute coordinate positioning. G91 = Incremental coordinate positioning. G92 = Absolute zero pre-set. Note: An old format to set XYZ zero and although still sporadically used, avoid this code if you can as it conflicts with Machining Center home positioning. G94 = Feedrate is read as Inches/Minutes. G98 = Return to Initial Plane (Drilling Cycle application). Used for high retract clearance when moving between drilled holes. G99 = Return to “R0” Clearance Plane (Drilling Cycle application). Used for retracting the tool to the “R” plane when drilling cycle is finished. Standard M Codes

M00 = program stop M01 = optional stop M02 = end of program (no rewind) M03 = spindle on CW (clockwise rotation) M04 = spindle on CCW (counter clockwise rotation) M05 = spindle stop M06 = tool change M07 = coolant ON (mist) M08 = coolant ON (flood) M09 = coolant OFF M19 = spindle orientation ON M20 = spindle orientation OFF M30 = end of program (rewind stop) M98 = call sub-program M99 = end sub-program55 thru G59 = Work coordinate shift (Fixture offset #2 thru #6) Note: Not all of these M Codes work on all machining centers.

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