Why?

[CharlieM]

I writ my own simple G-Code's to cut out simple parts. When cutting arcs (G02 and G03), why would I need to use I and J to define the center of radius instead of R?

[beege]

Of course it depends on your controller. Some don't take R words. On simple parts, its easier to use R. Just remember on arcs greater than 180° of sweep, some controllers require a negative R. If you don't want to have to remember that, or if you are making full circles, than I, J is a good habit to get into. This, too... some controllers' I nad J mean different things; some its the relative distance from the start point to the center, others its the absolute coordinates of the center point. (Just use R, okay?)