(C) Allowing Adequate Clearances For Cutting Tools

At the junction of a reduced-diameter shaft to the main body, the shoulder should not interfere with the cutting tool, as it does in (a). A relief groove or neck is desirable to free the tool after cutting (b). Note: Short screws in which the threads are formed by thread-rolling or thread-milling do not always require relief . The latter saves machining and increases part strength.

To avoid interference with the machining of the upper surface, U, surface A should be moved outward and the upper surface, U, should be redesigned to lie in one plane, if possible, so as to allow single-pass machining.

For internal boring or drilling (a), add a relief groove as in (b, C) for tool clearance.

The same applies to internal grinding (a). A clearance hole should be added (b) so that the grinding wheel will run freely after completion of its task.

Always allow free drill exits, especially with hidden inclined ribs.

Similarly, allow clearances for shaping and planing tools. Ditto for milling cutters and grinding wheels.