It's episode #97 and I've got another JayBurn Journal for you. A technical article written by Jay Burnham-Kidwell. He's a longtime blacksmith residing in Arizona, Since 1974, he has worked in various mediums and exhibited his work throughout the world. He works as a studio artist, lecturer, and demonstrator in all kinds of metalsmithing including jewelry, copper hollow forms, and blacksmithing. He's written more than 40 technical articles for various magazines such as the Anvils Ring and Anvil Magazine. So a JayBurn Journal titled "Punches, Drifts, Hammers and Top tools".
Show Notes:
- To produce a tool of quality the smith should use tool or alloy steels.
- Tool steels can be bought new or as a drop or discontinued stock or as "road kill" recycled steel scraps.
- The average blacksmith shop has adequate resources to forge, normalize, anneal and heat treat many tool steels safely and most available tools steels can be forged and heat treated by using modified methods of the manufacturers recommended procedures.
- Steel is a body-centered cubic crystal at room temperature. When heated to critical temperature, iron and steel undergo a phase change and become a face-centered cubic crystal structure. The hardening process changes the internal structure of the steel to form austenite. When quenched, the austenite is transformed into martensite, the hardest constituent in steel.
- Most tool steels generally trade one quality for another: wear resistance vs. toughness and accuracy vs. red hardness. Wear resistance is preferable when the tool must hold an edge or stand up to continued service. Toughness is needed for tools that are used under stress that may cause breakage. Accuracy addresses machining after forging and the ability to retain shape after heat treating. Red Hardness is the ability to retain shape and hardness when used at high temperatures (punching, chiseling, drifting).
- Normalizing – most, but not all, tool and alloy steels are normalized after forging by air cooling to remove most of the stress introduced by the forging process.
- Annealing – heating to critical temperature (nonmagnetic) and slowly cooling will restore varying degrees of softness in tools steels. This requires burying the steel in wood ash, lime, dry dirt or sand. You can use vermiculite, but know that you should wear a respirator because it contains asbestos.
- Machining – Most, if not all, tools require some grinding, filing or sanding after forging and before heat treating, as annealed steel is in a softer state and is obviously easier to grind or sand.
- Hardening – tool steels are heated to a specified critical temperature and quenched in the correct medium for optimum hardening. Tools steels are usually classified as air, water or oil hardening. Air hardening is accomplished by heating to critical temperature and cooling in still air. Water hardening is usually done in a 5 – 10% brine solution. Oil hardening is accomplished in commercial heat treating oils or vegetable oils.
- Tempering – hardening will produce maximum hardness and must be softened or tempered because the steel is too brittle at this point. The tool should be tempered as soon as possible after hardening. Tempering temperatures usually run between 300 – 600 f.
- W-1 tool steel – a straight carbon, water hardening tool steel that tends to chip or break. Old files were made from W-1
- O -1 tool steel – a straight carbon, oil hardening steel classified for coldwork, chasing and repousse.
- S series tool steel – very tough and exhibit very good red hardness. Due to varying amounts of tungsten and chromium, it can be a bit tough to forge.
- 4140 – a chromium molybdenum alloy steel that has great toughness, resists torque and can be used as punches, hammers and top tools.
- 4340 tool steel – a close relative to 4140 but with some added nickel. NEVER quench or cool in water, use only oil.
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