Old timer told me to quench in warm oil instead of cold... took me 150 knives to finally listen

Been forging blades for about 6 years now and I always used cold canola oil for quenching. Some retired smith at a hammer-in in Missouri told me my technique was wrong, that warm oil around 130 degrees gives better results. I argued with him for a solid ten minutes saying cold makes sense because it cools faster. Finally tried his way after cracking my 40th blade in a row last winter. Now I heat my oil to 130 on the dot and my edge retention improved maybe 30 percent. Anyone else stubbornly ignore good advice for years before giving in?

3 comments

3 Comments

davis.ruby26d ago

The Japanese sword thing is actually a common myth that gets spread around. They heat treated in water yes, but it was specifically for the edge, and they used clay to slow the cooling on the spine. The water itself was often around room temperature, sometimes even slightly warm, but not hot like 130 degrees. That would be way too slow for edge hardening on a katana. The idea they used warm water for the whole blade is a misunderstanding of how differential hardening works. Still though, your point stands about stubbornness. It took me cracking a tanto in half before I bothered to check my oil temp with a thermometer. I felt REALLY stupid after that.

susanm5626d ago

Read somewhere that the ancient Japanese smiths used to quench in warm water for their katana blades, something about the martensite structure forming better at a controlled temp. Makes me wonder how many secrets got lost over the centuries that we're just rediscovering now lol. I've been using warm oil for about two years after a similar old guy yelled at me at a guild meeting, and honestly my failure rate dropped from like one in five to maybe one in twenty. That whole "cold is faster so it must be better" logic is so stubborn too, I fell for it for way too long. Funny how we gotta learn everything the hard way even when someone's standing right there telling us the shortcut.

grantp2826d ago

Absolutely jumped on that "cold is faster" bandwagon myself for like three years. Thought I was being smart, using ice cold brine on some chef knives. Cracked three in a row before this old timer at a hammer-in just shook his head and showed me his warm oil setup. Switched to canola oil heated to about 130 degrees and it's like night and day. Still screw up sometimes but not near as often, and the steel just seems to behave nicer, you know? That whole thing about secrets getting lost really hits me too. I heard this story about a smith in Kyoto who would only quench at dawn because the temperature was just right, and everyone thought it was superstition but maybe he just knew the exact sweet spot for his shop.