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Mach4 General Discussion / Re: Cutter compensation (milling)

« on: November 15, 2020, 01:14:01 AM »

It looks like you solved your problem.  However, in the event this helps clear things up further, most commercial cnc machines, machine controllers, and cad/cam software packages use cutter comp the same way.  A negative cutter comp value would signify that the tool is smaller than programmed for, and will move the center of the cutter closer to the edge being cut, which will result in removing more material from both inner and outer contours, making inside holes and pockets (i.d.) bigger, and out side dimensions (o.d) smaller.  The opposite is true.  A positive cutter comp value signifies that the tool is larger than programmed for, and will result in the tool being moved farther away from the programmed edge and leave more material on the part.  typically, the cutter comp value entered is treated like a diametric value, and will result in the tool being move half that distance away from the programmed path.  For example, a -.010" cutter comp value with result in the tool (let's say a .250"Ø end mill) being treated as though it is really a .240"Ø end mill, and this will result in the tool path being adjusted so the tool is moved .005" closer to the programmed part edge, effectively removing .005" more material that it would have otherwise.  in and hole being milled in to a part, .005" of extra material would be around the entire perimeter of the hole resulting in the i.d. of the hole to be .010" larger.