Threading Both Ends of a Through Hole

The Problem: The customer's part print specified a straight pipe thread on both ends of a through hole. The customer desired to minimize the number of operations needed to machine the complete part, and also to minimize mislocation between the drilled through hole and the bottom thread which would typically have been threaded in a separate operation after the part was flipped over and refixtured.

The Solution: A custom made extended length Widia GTD (formerly Greenfield) PM Plus Thread Mill with a neck.

This tool allowed the through hole to be drilled and the threads at both ends of the hole to be milled in one operation, eliminating the need for a separate threading operation.

The thread mill first entered the hole and milled the threads at the bottom of the hole (the extended length, necked shank prevented the tool from interfering with the top portion of the hole during this operation.) Next the tool pulled out of the hole to allow flushing of chips. Finally the tool reentered the hole and milled the threads on top.