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I posted a message (here on I Forge Iron) asking for some insight when I was given some "to be discarded" wood planer blades. The responses were very helpful and encouraging. Since I cannot heat treat the metal (that seems to have been) used to make these blades, I have started making some quick little project knives to help me learn more about knife making and working with hardened steel. So far I have made two little knife like objects that are both even useful. The planer Blades are approximately 12.5 inches x 0.75 inches x 0.06 inches. The blades a laminated M2 Steel. As I understand so far, M2 steel is more hard than it is tough so I will avoid using it for applications requiring impact resistance -- or where failure is likely to lead to injury or death.
What do you think...? The Story I was given used/discard planer blades that I wanted to anneal and use as raw material for other items (e.g. little knife blades). They are M2 High Speed Steel. I have been reading a lot of information about using scrap steel from this and that--I really like the idea of repurposing material that would otherwise be thrown away. For example: It apparently use to be true that you could get saw blades from a mill and cut them up to make tools. After looking into the thermal treatment guidelines for M2 steel I think I would be better off buying an appropriate material. I am starting to think that the info I've read that questions the wisdom and economics of trying to use "unknown steels" may be more right than I had hoped. That trying to use "scrap" is likely to be a frustrating, often fruitless, and maybe even dangerous activity. I will appreciate your thoughts and experience with using discarded material -- especially as it relates to the Anchorage and The Valley regions of Alaska. ------------------------------------------ M2 High Speed Steel Thermal Treatments HEAT TREATING INSTRUCTIONS HARDENING Critical Temperature: Ac1: 1530°F (832°C) Ac3: 1610°F (877°C) Ar1: 1430°F (777°C) Ar3: 1380°F (749°C) Preheating: To minimize distortion and stresses in large or complex tools use a double preheat. Heat at a rate not exceeding 400°F per hour (222°C per hour) to 1100°F (593°C) equalize, then heat to 1450-1550°F (788-843°C). For normal tools, use only the second temperature range as a single preheating treatment. Austenitizing (High Heat): Heat rapidly from the preheat. For Cutting Tools: Furnace: 2200-2250°F (1204-1232°C) Salt: 2175-2225°F (1191-1218°C) To maximize toughness, use the lowest temperature. To maximize hot hardness, use the highest temperature. For punches, dies, and tools that require maximum toughness without hot hardness: Furnace: 2075-2175°F (1175-1191°C) Salt: 2050-2150°F (1121-1177°C) Quenching: Pressurized gas, warm oil, or salt. For pressurized gas, a rapid quench rate to below 1000°F (538°C) is critical to obtain the desired properties. For oil, quench until black, about 900°F (482°C), then cool in still air to 150 -125°F (66-51°C). For salt maintained at 1000-1100°F (538-593°C), equalize, then cool in still air to 150 -125°F (66-51°C). Tempering: Temper immediately after quenching. Typical tempering range is 1025-1050°F (552-566°C). Hold at temperature for 2 hours, then air cool to ambient temperature. Double tempering is required. For large cross sections, and especially for blanks from which tools will be cut by wire EDM, triple tempering is strongly recommended. ANNEALING Annealing must be performed after hot working and before re-hardening. Heat at a rate not exceeding 400°F per hour (222°C per hour) to 1525-1550°F (829-843°C), and hold at temperature for 1 hour per inch (25.4 mm) of thickness, 2 hours minimum. Then cool slowly with the furnace at a rate not exceeding 50°F per hour (28°C per hour) to 1000°F (538°C). Continue cooling to ambient temperature in the furnace or in air. The resultant hardness should be 248 HBW or lower.