CNC Arc motions

Circular interpolation is quite a bit more demanding on your machine as two axes have to be precisely coordinated. Drawing a complete circle involves not just coordinated motion but reversal of direction at each of the 4 quadrant points. These would be the points corresponding to 0, 90, 180, and 270 degrees. If the machine has any backlash at all, it will be obvious at these reversals because there will be a glitch in the cut there