Method of making barrel-shaped worm-like tool

A method of dressing a barrel-shaped worm tool that uses a dressing tool to dress the barrel-shaped worm tool, the barrel-shaped worm tool is used for gear-machining an internal gear to be machined by the barrel-shaped worm tool and has a diameter gradually increasing from ends in an axial direction to a center in the axial direction of the barrel-shaped worm tool, the dressing tool is an internally toothed dressing gear having a smaller number of teeth than the number of the teeth of the internal gear to be machined, the method comprising:

• providing the internally toothed dressing gear having the smaller number of teeth than the number of teeth in specification data for the internal gear to be machined;
• engaging the provided internally toothed dressing gear and the barrel-shaped worm tool with each other at the same axis intersection angle as during gear-machining to be performed by the barrel-shaped worm tool;
• and
• dressing the barrel-shaped worm tool using the internally toothed dressing gear.