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G3 Counterclockwise arc
Mach3 Mach4 G-code · Mill
Cuts a counterclockwise arc at feed rate in the active plane. Give the center with I J K or the radius with R.
Format
G3 X Y [Z] I J F or G3 X Y [Z] R F
Addresses
| Address | What it does |
|---|---|
X Y Z | End point of the arc |
I J K | Arc center, from the start point or absolute per IJ mode |
R | Radius, negative for more than 180 degrees |
F | Feed rate |
How it works
Modal, motion group.
Example program
G0 G20 G90 G54 G17 G40 G49 G80 (SAFE START, INCH)
T1 M6 (TOOL CHANGE)
S2500 M3 (SPINDLE ON)
G91.1 (INCREMENTAL IJ MODE)
…
T1 M6 (TOOL CHANGE)
S2500 M3 (SPINDLE ON)
G91.1 (INCREMENTAL IJ MODE)
…
The full 9-line example is in the app. Example is in inch. Check offsets and clearances first.
Watch out for
- Mach has an IJ mode setting. Incremental IJ is normal for Fanuc style posts. If arcs show as huge wrong circles, the IJ mode does not match the post.
- Set the IJ mode with G90.1 or G91.1 in the program so the setting in the configuration cannot catch you.
- R with a negative value cuts the arc over 180 degrees. Use I and J for full circles.
Related codes
G3 on other controls
The same number can mean something different on another control.
| Control | Meaning |
|---|---|
| Fanuc | Circular interpolation counterclockwise |
| Haas NGC | Circular interpolation counterclockwise |
| Mazak (EIA) | Circular interpolation, counterclockwise |
| Okuma OSP | Circular interpolation counterclockwise |
| Mitsubishi M70 M80 | Circular move counterclockwise |
| Brother Speedio | Circular interpolation counterclockwise |
| Siemens 840D 828D | Circular interpolation counterclockwise |
| Heidenhain TNC (ISO) | Counterclockwise arc, Cartesian |
| Fagor 8055 8065 | Counterclockwise circular interpolation |
| LinuxCNC Tormach | Counterclockwise arc or helix |
| Centroid CNC12 Acorn | Counterclockwise arc or helix |
| Hurco WinMax (NC) | Circular or helical move counterclockwise |
| Fadal | Circular interpolation counterclockwise |
| Swiss (Citizen Star) | Circular move counterclockwise |
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