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Making a knife out of a lawnmower mulching blade? Answered

I am planning to use a lawnmower mulching blade to make my first knife. I need to know how should I heat treat the blade. I have read about annealing, quenching and tempering but every source of information has different instructions. Since I am planning to do this outdoors, I thought about using motor oil for quenching. Would you please provide some ideas or suggestions? Thank you very much for all your help.


Make sure you have your blade fully shaped and polished to the texture you want before you try tempering it. Once it's well tempered you will have a hard time shaping the blade. Then start heating the blade up as evenly as possible. You'll know the blade is hot enough to quench it if a magnet is no longer attracted to it. Then you can quench it in motor oil. be sure to dip the blade up right and not on it's side or you could warp the blade.

Water is the recommendation if you are sticking to old blacksmithing traditions. Any modern blade is quenched in oil which helps ad carbon to the blade further strengthening it. Even tool manufactures use oil to help harden the tool's metal.

Yes it's the last thing you do. Get the edge where you want it and everything before you temper it. You will have to re polish it and touch up the edge after tempering it but you want that all pretty much done before you temper it.

Blkhawk, I think that mulching blade is not appropriate to make a knife. It can not be hard steel because turning at high speed, if it breaks would be a mortal danger.

i have only made one knife that i heat treated (using an oxy-propane torch) all my other knives I'm just careful not to overheat the steel. i do the rough shaping with a bench grinder (again, if the steel gets too hot to touch, dip it in a bucket of water to cool it off. DO NOT WEAR GLOVES) then i do everything else with hand files and sandpaper. sure its a lot harder, but for me its easier because you always get a perfect factory heat treatment. some people will disagree but this way works for me and I've never had a blade break or bend. i would recommended Wayne Goddard's book '$50 dollar knife shop' for anyone wanting to make a knife. and yes the lawnmower blade will work fine, its probably 1080 or 1085 steel.

no problem. i think anyone wanting to cheaply make a knife should read it. its a really good book.