HHIP 12P #1 14.5 degree gear cutter diameter is 2 1/2 inch. The bore is 2.5 cm. Made of high speed steel. Made from solid ground. Glossy finish. Straight teeth on the edge of the cutter. For spur gears with 14.5 degree & 20 degree involute gear cutters make it possible to machine gears on your CNC or manual router. The gear cutter is made into the tube profile that transfers its shape to your gear blank so it can be operated with other gears. The gear cutter must be matched to your transmission specifications, including diameter pitch or module, pressure angle, and the number of teeth it will cut. The profile of all involute spur gears changes slightly with the number of teeth and so the profile of the gear cutter changes. The cutters are numbered from #1-#8 depending on how many teeth it cuts.