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Andy Dingley Andy Dingley is offline
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Default Blueing/oil quenching of mild steel

On 3 Aug, 12:30, 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".



Hot oil: Heat them up (not glowing) and wipe with oil. Vegetable oils
give browns, clean engine oil gives blues, old engine oil gives black.
Not rustproof against weather. You only need a gas blowtorch to heat
the steel up, then wipe with an oily paper towel. Use paper, as it's
easier to extinguish than rags. Wear a good leather welder's glove
when doing this, and not one with a hole in!

Cold blues: Selenium compounds. Phillip's is best (gunshop),
Birchwood Casey a long way behind. Follow instructions. Cleanliness
and degreasing with acetone is vital. Toxic. Not rustproof.

Browning. Controlled rusting to give the finish of old steelwork or
shotguns. Read a pre-war gunsmithing book. Harder than it sounds to
get good results.

Weatherproof bluing. Look up "Parkerising", buy the kit from Caswells.
Complicated.


Hardening, tempering and quenching relies on using a steel with some
useful amount of carbon in it, not mild steel. Carbon won't migrate
from an oil quench. For a good text on hardening, knifemaking books
from Barney & Loveless (cheap), Wayne Goddard or Jim Hrisoulas
(excellent) are good primers. 1950s engineering textbooks are pretty
good too. Weyger's book is crap.

If your steel has insufficient carbon to start with, add some by case-
hardening. The wikipedia article is decent.