TIL I was over-tempering my chisels for 8 years, a cracked edge in Denver showed me

I thought harder was always better. I was running my chisels at a bright straw color and then quenching in oil, figured that meant max edge holding. Last month a guy brought in a vintage cold chisel that he wanted re-done for a demolition job on some old cast iron. I did my usual heat treat, and first hit, the edge chipped out like a potato chip. He looked at it and said, 'man, that's way too brittle, did you even draw it back past the blue?' That stopped me cold. I'd been skipping the second tempering step because I thought it was for soft heads, not cutting edges. I pulled out my backup chisel, tested it, and sure enough it had micro cracks at the tip. Now I run everything to a light blue, around 560 degrees, and hold for an hour. Has anyone else found that the common hardening charts are flat out wrong for steel you use every day?

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robinl9013d ago

That 'harder is always better' mindset is everywhere, not just in tool steel. I've seen it with people over-tightening bolts, over-filling tires, even over-cooking steak, and it always ends with something cracked or ruined. Your Denver story is a good reminder that the right balance usually beats the absolute max, in metal and in life.