Forging High-Carbon Tool Steel

Used in

• Chapter 3 The Knife

The rows that check it

• 13 confirmed
• 2 amended
• 2 unresolved
• 6 marked for safety

• K1 confirmed Safety The oil quench flares at the surface every time; the can is steel, tall, 5 litres or more, lidded, no water near; leave the blade in, lid on, never water on burning oil
• K3 unresolved Safety As-quenched blade is glass-hard and can shatter if dropped; temper within the hour or it can crack on the bench by itself
• K4 confirmed Safety Dust from natural stones and linings is respirable silica; wet work only
• K5 amended Safety Carbon monoxide at the forge and zinc fume from galvanised steel apply here as before; zinc vaporises above 400 °C
• K6 confirmed Safety Never quench a file, spring or blade in water
• K8 unresolved Safety Steel struck below dull red (650 °C) cracks inside and breaks in the quench
• K14 confirmed The change at 730 to 760 °C for plain carbon steel; the shadow of decalescence; the magnet lets go at about the same heat
• K15 confirmed Quench must pass 600 to 550 °C in about a second (the nose); martensite skates a file; only about 0.6 % carbon in solution before lath gives way to plate; hotter is not better
• K16 confirmed Temper 200 °C two hours twice; light straw 200 °C at 60 HRC; bronze 240 a warning; 230 to 315 the brittle trough (TME); 345 and up grey-blue spring temper for axes, hoes and forks
• K17 confirmed 1084 is 0.80 to 0.84 % carbon, hardens in fast oil from a plain forge with no soak; leaf spring 5160 about 0.6 % C with chromium, deeper hardening, slow oil, cracks in fast; file …
• K20 confirmed Forge 1084 and 5160 at orange-yellow 980 to 1,060 °C; stop at dull red 650
• K21 confirmed Bevel forging curves the blade backward; edge left 1 mm ("a coin") before the quench or it ripples (bacon edge); pre-curve the tip upward in the last heat
• K22 confirmed Normalise three times: 900, 815, 730 °C in still air; grain to a few thousandths of a millimetre; the triple quench is a myth that cracks blades
• K23 confirmed Harden 1084 at 800 to 815 °C, 5160 at 830; point first; fast quench oil for 1084, canola at 50 °C for 5160; move up and down, never sideways; vapour jacket
• K24 amended Scale and decarburisation: a thin edge can lose its carbon a millimetre deep; muffle pipe with charcoal inside; or grind the skin off after the quench
• K49 confirmed Cooper's steels: froe 5160 at 48 to 50 HRC with a 30° edge, axe 22° at 56, hollowing knife W1 tempered 200 °C at 60, jointer 52100 at 60 to 62, croze 58, adze 54 to 56
• K50 confirmed The fork's tines are hardened at 830 °C in warm canola and tempered grey-blue, 345 °C or above, like the broadfork's

In the Index

Iron and steel Tools and their making