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Pete Verdon Pete Verdon is offline
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Default Blueing/oil quenching of mild steel

Dave Osborne wrote:
When I was a lad, if memory serves correctly, we used to dip hot ferrous
parts into a bucket of old engine oil. This gave them a blue/black
finish and I'm pretty sure we called it "blueing".


I remember doing this at school, too. This was recently enough for the
subject to be called "Design and Technology (Resistant Materials)", but
was essentially still metalwork taught in the metalwork workshop by
crusty old metalwork teachers :-).

Can anyone put me straight? I was idly thinking about DIY oil quenching
to achieve moderate rust-resistance.


The other day in my dad's garage I came across the mild steel gadget
that I made in 3rd-form DT. The surface didn't look all that great
(probably didn't when new either :-) ), but it wasn't rusty. So I reckon
"moderate rust-resistance" is about right.

Do I need to use old engine oil, or will new be good/better/safer?


I do remember the aforementioned crusty old teacher telling us that the
older the oil, the better.

ISTR we heated the parts up to a dull red before quenching. Does this
sound right?


I think so.

Pete