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G3 Counterclockwise arc or helix / Counterclockwise arc

Centroid CNC12 Acorn G-code · Mill, Lathe

On mills: Counterclockwise arc or helix

Cuts a counterclockwise arc in the active plane. Give the end point and either R or I J K. Adding the third axis makes a helix.

Format

Addresses

How it works

Modal, motion group. Stays on until G0, G1 or G2.

Example program

The full 9-line example is in the app. Example is in inch. Check offsets and clearances first.

Watch out for

• Use I J K for a full circle. R cannot make a 360 degree arc.
• A helix uses the same G3 with a Z end point. The feed is along the full helical path.

On lathes: Counterclockwise arc

Cuts a counterclockwise arc in X and Z. Give the end point and R, or I and K to the center. I and R are always radius values.

Format

Addresses

How it works

Modal, motion group.

Example program

The full 9-line example is in the app. Example is in inch. Check offsets and clearances first.

Watch out for

• Convex OD arcs moving toward minus Z are G3, such as a radius on the end of a shaft.
• A lathe can cut at most a 180 degree arc.

Related codes

G2 · G17 · G42

G3 on other controls

The same number can mean something different on another control.