Black oxide

[Herbiev]

Hi all. I have tried a few methods of getting that black oxide finish we see on machine tools socket head cap screws and alike but I always end up with a patchy brown/black finish that just wipes off. Does anyone know how the proffesionals get that long lasting even finish?
TIA
Herbie

 

[hammer2100]

I have good luck with Brownell's OXPHO-BLUE. You have too make very sure to clean all oil off parts. I'll put parts in small oven a preheat to get oils out of metal sometimes this takes 2or3 times. This is a long lasting finish if you do it right. Almost as good as hot salt bluing. It helps if you totally submerge parts. Give some a try.

 

[Herbiev]

Thanks Mark. I'll give it a try.

 

[Tin Falcon]

MSC and others sell tool black .
Another method I have used and is chap and easy .
I made some grippers for my metal scroll bender. a little knurled cam deal. I wanted them hardened so just heated to red hot and dipped in used motor oil mix. My own blend of 4 parts Quaker state 5w30 and one part marvel mystery oil mixed for about 3000 miles in a ford engine. If you are in the area I can give you a couple quarts.
It gives a beautiful black oxide finish.
Tin

 

[Herbiev]

Thanks Tin. I wont be in your area in the foreseeable future but I do have a ford that leaks oil. I'll stick a tray under the sump and give it a try ;D

 

[rhitee93]

I have used the motor oil trick for years to create black hardware. I use new oil, but the results are good.

I heat the part to a dull red, pull it out of the flame for about a second, and then drop it in the oil. This will usually result in a black finish with some crusty brown spots. I then reheat it while it is still coated in oil to a point that it just starts to glow and drop it back in the oil. The result is usually a nice black finish.

I use this technique often to darken modern hardware. However, you have to get all the zinc plating off or it won't work. (Not to mention the toxic fumes) I use muratic acid to eat off the plating.

I've never tried it on a large part. I suspect it would be difficult to get an even finish.