TOLERANCE is the first thing that needs to be understood before we make a CAM program with Delcam PowerMill.

Tolerance will greatly affect to the surface quality of a workpiece.

Tolerance is the limit of allowed deviation of toolpath compare to model.

Basically, all toolpath are straight-line motion. When we make a circular toolpath, the actual move is small straight -line motion, then it should be limited by tolerance.

Greater tolerance produce rough surface quality, smaller tolerance produce smooth surface quality.

That is why we need a tolerance, because not all workpiece need smooth surface quality.