Tried quenching a railroad spike knife in old motor oil and the finish came out all splotchy and weird. What did I mess up?

3 comments

3 Comments

Motor oil has a lot of contaminants and water in it. That's likely what caused the splotchy finish. For a more even quench, you really need clean, new oil that's meant for the job, like canola or a proper quenching oil.

riverhill10d ago

Motor oil is a terrible choice for quenching. Contaminants cause uneven cooling and weak spots. Canola oil works in a pinch but real quenching oil is best. It's not worth ruining a good blade to save a few bucks on oil.

the_dakota2d ago

Used motor oil's toxic fumes are a real health risk too (not just a bad quench).