View Full Version : Black Finish

03-10-2005, 06:46 PM
How do you finish steel black like machine tools are?

03-10-2005, 06:49 PM
Try this....


or MSC also has something called tool black.

There is a do it yourself thing you do with heat and linseed oil.

[This message has been edited by IOWOLF (edited 03-10-2005).]

03-10-2005, 07:31 PM
Check this out too:


03-11-2005, 08:18 AM
My high school shop teacher tought us to use old used oil....you know the really black stuff...and you just heat and quench in many times....the more you do it the blacker it gets...ocassionally it comes out a lil splochy...but with enough quenches that will disapear...it's actually quite fun....but keep something to cover up the pan you have the oil in....because if you leave the part too hot when you quench...it could light the oil on fire...so use something to starve it of it's oxygen...i think this way is one of the funnest...and a good way to motivate you to change the oil in you car

03-11-2005, 09:21 AM
I have used the oil trick before and have been happy. But who wants to use only one method? It would be nice to have a real bluing job on your new made item. So the question comes up.

How hard is it to get Ammonium nitrate? Do I have to sign my life over due to new terrorism laws? Anyone had problems?

03-11-2005, 10:04 AM
This has been asked before, so you may want to search the archives.

Basically, the black is an oxide of iron. It's like plain old orange rust, except the black oxide has a different number of oxygen atoms tied up with the iron atoms than common rust dows. It's like gun blueing.

There are two major ways to get this: a hot process and a cold process. The hot process gives a more durable result, but it involves the use of some pretty nasty, caustic chemicals. The cold process is simple -- just clean the surface and swab on the blueing or blacking solution -- but the results aren't as durable and probably not as good-looking as a good hot blueing or blacking job.

You can buy the cold blacking kits from places like MSC www.mscdirect, (http://www.mscdirect,) or small bottles of cold gun blueing from sporting goods stores or Brownell's www.brownells.com (http://www.brownells.com) . Brownell's also sells all the hot blueing supplies and has lots of information about doing it, if you want to try it. Get a copy of their book "Gunsmith Kinks #1" for lots of information about both hot and cold blueing.

Paul Gauthier
03-11-2005, 11:01 AM
www.precisionbrand.com (http://www.precisionbrand.com)

Paul G.

03-11-2005, 12:56 PM

how hot does something have to be for this to work? is it something a propane torch can do, or have i finally reached the point where i have so many projects that can use a "real" torch that i need to seriously start looking for one? i know, i know, how can i call my self a metalworking hobbyist and not have a decent torch.

andy b.

03-11-2005, 02:14 PM
I parkerize everything. It's a hot process (~180 degrees), but much less so than hot blueing. Most tool steels will come out with a very dark charcoal color. The crystaline structure of the surface finish holds oil very well.

If you want a true black finish, hot blueing or black oxide is the trick. For black oxide, there is a cold process that works faily well from Caswell. I have used it with good results but I prefer the park finish, as it seems much more durable.

That's my story and I'm sticking to it...

03-11-2005, 03:02 PM


R. H. Angier. 155 pages. 51/2" x 81/2". Hardbound. A practical treatise covering the art of rust-type gun bluing. Some 300 formulae for various steels and processes with complete instructions, explaining how guns can be oxidized with solutions compounded at home. For the gunsmith or hobbyist.

Have Fun
Be Safe http://bbs.homeshopmachinist.net//smile.gif

03-11-2005, 08:12 PM
True black oxide is a mixture of Amonium nitrate (fertilizer) and Sodium hydroxide (drain opener) and water heated to 285 deg F. The part needs to be clean and soaked in an acid bath. Don't recall the acid name but gives the steel surface a Ph that enhances the blackening process. After the black oxide process (about 20 minutes) the part is rinsed in cool water and them emersed into a rust inhibiting oil.

I have had access to a hot black oxide tank where I work for 28 years and use the system about once a month for company projects and also personal projects.

Nothing compares to the hot black oxide process. Tried the Tool black and feel it is a waste of money. However, quenching hot steel parts in oil seems like the best alternative for home use.

03-11-2005, 09:47 PM
I don’t know how others heat the parts that they dip in oil but I heat mine at home with an oxy/acc torch until the part is a dull red color and then dip in oil. I don’t know if a propane torch will get thicker stuff hot enough. Anyway, dull even red is what I shoot for over the part and then in the oil. A few repetitions and the part has a nice finish.

I used this method on the cross bars of these chuck handles. No rust yet and they still look nice.

Lathe chuck key (http://img.photobucket.com/albums/v12/rockrat/DSC01515.jpg)

[This message has been edited by rockrat (edited 03-11-2005).]

Dick Plasencia
03-12-2005, 05:53 PM
I've tried tool back and gun blue and I like the gun blue better and it is cheaper. But I also use oil blackening and that by far is the best. The piece becomes rust proof. At least the ones I have done which include large screws do not rust. The color can be anywhere from a dark honey to black as coal. The heating and type oil is important. I coat my part with motor oil and place it on an electric hot plate and let it cook until black. Takes under one hour. You can also heat it with a propane torch and dunk in oil. I just wish I could do the same with aluminum.


03-12-2005, 06:23 PM
Birchwood-Casey just brought out a system for under $600. Probably too big for the home shop but might be of interest to the small job shop. Temp of 185 degrees.


They also some other room temp products in smaller & less costly quantities:



[This message has been edited by precisionworks (edited 03-12-2005).]