Case Study #7

Part Name: Trimmer rotor

Material: 360 brass

Challenge: Turn an OD to .204 ± .0003 with a surface finish of 16 RMS for a length of 1", cut #8 -100 threads (100 turns per inch, with a major diameter consistent with a #8 machine screw) over a length of over .9", mill a slot in the end, and maintain concentricity, straightness, and roundness to near-perfection, while minimizing cost.

Solution: The body of this piece makes it a classic Swiss part - a length-to-diameter ratio of five, and very tight tolerances. The thread presented challenges, however. We ran this in the Tsugami CNC Swiss Screw machine, with the piece "inverted", and single-point threaded it while the body was held by the sub spindle for support. The almost robotic flexibility of the Tsugami aided in the handling of the delicate part after cut-off. With a thread height of only a few thousandths, we modified the threading tool to reduce the tool nose radius to zero.