See also TURN for helix interpolation Consider: ( Four main methods of programming an arc: NOTE START is where current tool position is 1./ Center(XY) + End(IJ) 2./ Radius(CR) + End(XY) 3./ Aperture angle (AR) + Center(IJ) 4./ Aperture angle (AR) + End(XY) [5./ AP=... RP=... ; Polar coordinates, circle around the pole] FULL CIRCLE IN ONE BLOCK: Must specify and CENTER POINT AND END POINT e.g: Move to 10,20 (start point) , G02 X0 Y0 I10 J20 (center 0,0 and end is same as start) RADIUS ISSUES For circles with radius specification, the arithmetic sign of CR=... is used to select the correct circle. It is possible to program two circles with the same starting and end points, as well as with the same radius and the same direction. The negative sign in front of CR=-... determines the circle whose circle segment is greater than a semi-circle; otherwise, the circle with the circle segment is less than or equal to the semi-circle and determined as follows: Using Polar Coordinates N1 G17 ; X/Y plane N5 G90 G0 X30 Y40 ; Starting point circle for N10 N10 G111 X40 Y33 ; Pole = circle center , define pole as being at 40,33 N20 G2 RP=12.207 AP=21 ; Polar specifications