TABLE OF CONTENTS In a machining environment, stock allowance is a term that defines the amount of material left for finishing after rough cutting had been completed. Although it seems a subject simple enough to ignore, there are some considerations that will influence the programming techniques applied to roughing, particularly the last tool passes, where the stock will applied.
The major considerations of stock selection and control are the nature of the cut, particularly the shape of finished contour, and the type of tool used. Leaving stock on the roughed contour is generally designed for the finishing cut, but there could be other reasons, for example, as a grinding allowance. When using the G71/G72 lathe cycles, stock allowance can be defined in the cycle. If a cycle is not used, the required stock allowance must be programmed directly, even if it means a few additional calculations.
Most contour toolpaths will be a combination of lines and arcs, where the lines represent diameters, faces, shoulders, tapers and chamfers, while arcs represent fillet radiuses, partial radiuses, undercuts, etc. Stock left on an external contour will increase its nominal size, whereby stock left on internal contour will decrease its nominal size.
A typical cutting tool (external or internal) used on a CNC lathe may have several tip orientations, depending of the tool design and its direction when mounted in the turret. The standard turning and boring tools (with 80 , 55 , 35 inserts) mounted for typical working...
