High-Speed Steel Lathe Tools: Hardened White-Hot and Ground to Taylor's Angles (Becker, 1910)

Use annealed tool-holder stock: unannealed bar got its hardness from the rolls, not from proper hardening. Saw the pieces off (a band saw is better than a circular saw). Do not nick and break them: the break can start fine cracks that spoil the tool later.

Before hardening, grind each piece close to its final shape on a dry emery wheel. Leave a little to grind off afterwards, to remove the burnt skin and restore the edge.

In a forge fire covered with a firebrick hood, bring the tool slowly to a bright red, about 1,000 °C (1,800 °F). Then heat it quickly to a dazzling white, above 1,200 °C (2,200 °F), until the surface begins to flux and the corners start to melt. For roughing and medium cuts go as hot as you can without actually melting it; most high-speed steels do not melt below 1,400 °C (2,550 °F). Red to white takes no more than about two minutes for a one-inch tool. Heat the nose right through, but keep the white heat out of the neck.

Hold the tool in a stream of cool compressed air, reduced to 2-3 lb pressure at the nozzle, and keep turning it until it is cold enough to handle. Then lay it aside in a dry place. Avoid cold water. Leave lathe roughing tools untempered.

For roughing tools use a coarse wheel: Taylor used grits 24 and 30 mixed, and a 20-combination also does. For finishing tools use about a 60-grit J-grade alundum wheel. Run the wheel at the speed its maker gives. Never let the edge get hot: high-speed steel starts to soften at about 550 °C (1,100 °F), and a hot face meeting cold water cracks. Grind the nose radius from the tool width A. Blunt tool: R = ½A − 5/32 in. Sharp tool: R = ½A − 3/16 in. Taylor's sizes run from ½ to 2 in wide.

Keep the clearance small, about 6°, as on all of Taylor's standard tools. Choose the rest by the metal to be cut: - Cast iron and harder steels (about 0.45 % carbon and up): lip angle 68°, back slope 8°, side slope 14°. - Softer steels: lip angle 61°, back slope 8°, side slope 22°. - Tire steel and similar hard steels: lip angle 74°, back slope 5°, side slope 9°. - Chilled iron: lip angle 86-90°. - Extremely soft steels (0.10-0.15 % carbon): lip angle about 61° or less. The harder the metal, the blunter the angle. The steep side slope lets the tool be reground more often without weakening it. Check the angles with a protractor.