How to Make a Form Tool Grinding Attachment for the Watchmakers' Lathe by Robert Porter

A FORM TOOL GRINDING ATTACHMENT

It is beyond the scope of this guide to get into the rather involved process of designing gears - there are several books available from horological book sellers that treat this subject in detail. This guide is about making the form tool you will use to make the gear cutter after you have the gear information you need. It is a lot of fun to see the complex geometry of a wheel or pinion emerge from a piece of steel or brass, especially when you have made your own cutter. Three types of cutters are shown in this guide.

This easy to make attachment will allow us to grind any radius and clearance angle we are likely to need on a cutter forming tool made from a 3/16" (0.1875") square high speed steel lathe tool bit. The tool bit is ground on a bench grinder to the approximate shape needed. The grinding attachment is used to finish grind the form tool only. Protect the lathe headstock, bed, and slide rest etc. from grinding grit with clear plastic clinging type food wrap, for example. 2001