I have battled with understanding how to code G2/G3 commands for cutting CW and CCW arcs for some time. Today, I was trying to get one CCW arc and then retrace that path CW .001 deeper. It was just not working in any way that made sense. Part of what makes these commands so hard is that the preferred format is
G2 Xend Yend Ixoffset Jyoffset where xend,yend is the final destination, xoffset and yoffset are distance from start point to center of radius. It is very easy to get these wrong. Aggravating this as ChatGPT explained is that linuxCNC will often get confused because of floating point math errors. It suggested using the generally less regarded format where you specify Rradius instead of I and J. What a difference!
Example: Starting at (.8250,0) to cut an arc to (3.3153,-2.153) using a .245" diameter endmill (nominal diameter .25"):
G3 X3.3153 Y-2.153 R2.153 F1
G1 Z-.001 F1 (lower cutter .001")
G2 X.8250 Y0 R2.153 F1 (go back to the start)
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