Thread cutters come in pairs and include a tool for exterior threads and one for cutting matching interior threads. Perfectly designed for making screw tight lids on boxes and caskets, this fascinating and practical aspect of woodturning includes a range of cutting tools that have been produced from High Speed Steel in 10, 16 and 20 threads per inch (TPI). They have been designed with a unique, enhanced helix angle specially designed for use in wood. To complement these tools, a range of optional items have been produced to provide a complete solution to thread cutting. These include: Relief Cutting Tool. Tool Support Rest – to make forming internal threads easier. Thread and Sizing Gauge – takes all the guesswork out of dimensioning.