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Oil Blackening (bluing) screws?

Posted: Fri Aug 25, 2017 5:28 pm
by Tommy Atkins
I find the need to oil blacken several screws, none really large.
As this is my first attempt I went online looking for info & found a bewildering set of temperature variations. They vary from "heating till the metal turns the shade of blue you want" to "red hot", & everything in between! It strikes me that red hot is going to change the hardness & temper of the screws, so whats the real story to blue with heat & oil? Do I heat, blacken, harden then temper or what?
I'm also being put off old motor oil for several reasons, but can easily use Linseed as I have plenty of it.
I have both a dedicated toaster oven & a propane torch for heat, which is gong to serve me better (assuming It will reach & sustain the temp I need)?

Re: Oil Blackening (bluing) screws?

Posted: Fri Aug 25, 2017 7:30 pm
by Rapidrob
Heat to dull red,dunk in motor oil. It will be black. I do it all the time. It will not take the temper out of the screw.

Re: Oil Blackening (bluing) screws?

Posted: Sat Aug 26, 2017 4:41 pm
by Tommy Atkins
Thanks, Rob. Someone else suggested Linseed, which I have, any thoughts on one Vs the other?

Re: Oil Blackening (bluing) screws?

Posted: Mon Aug 28, 2017 9:55 am
by Rapidrob
Just about any oil will work.When in doubt,try a scrap screw first.

Re: Oil Blackening (bluing) screws?

Posted: Thu Aug 31, 2017 9:16 pm
by bobvz
Linseed oil is fine. Yes practice on a few screw heads and you will get the technique down. Do the heating in reduced light so you can visualize the colors. On screws heat the shaft just below the screw head and let the heat migrate into the head. You can control the color better that way.