Mastering the lathe — part 7
It used to be the norm to grind turning tools to shape from stock pieces of high-speed steel (HSS). Then convenient tungsten carbide cutting tools with screw-on inserts became commonplace. However, hand-ground tools still have a place in the thrifty sheddie’s workshop and indeed in commercial workshops where a tool with a particular shape is needed.
Before HSS was developed, we had alloy tool steels. They would cut metal parts but would easily become blunt, even at slow cutting speeds. The reason was mainly that early tool steels became soft as they got hotter. The faster the cutting speeds, the hotter and softer the tool tip; the workpiece material was then harder than the tool, and the cutting edge failed.
Metallurgists discovered
