Sherline 3307 Sherline 10,000 RPM Headstock/Motor/Speed Control Unit- If you are purchasing a complete drive unit and need high speed capability, the P/N 33070 is a good choice. It can be installed in your own special tooling application or swapped with the standard Sherline unit on your lathe or mill in just a few seconds. Preload is already pre-adjusted to the proper setting from the factory.