Taps and Dies Cut on the Lathe, with Wrench and Stock

A tap cuts the thread inside a hole; a die cuts it on a rod. Makers made their own in the 16th and 17th centuries. Cut the thread on tool steel in the screw-cutting lathe, file flutes so it cuts, harden it, and use the finished tap to cut the thread in a steel blank that becomes the matching die. A T-wrench turns the tap, a stock holds the die. The picture: a tap held in a T-wrench.