Heat/Nitre bluing small parts

[dakota.potts]

I've seen some pictures recently of the different colors that are possible with heat bluing and nitre bluing small parts. I really like the purple/royal blue color that can be achieved for an accent. I have a couple of projects that I'm thinking about trying here in a couple of months with rust bluing a pistol and I think this color of blue would be very good looking for accents such as the trigger, hammer, safety, slide lock etc.

The process seems relatively simple. I looked at Brownell's and they have nitre bluing salts but only in 10 lb. increments. They also have a note that the salts have to be heated to a very high temperature (something like 600-700 degrees IIRC which seems extraordinarily high).

Does anybody know if it's possible to get good results with this process without the ability to reach such high temperatures? Can a controlled heat temper be easily accomplished to create the shade desired? Can this process really be done with tools as simple as a propane torch or small convection oven as seems to be suggested?

Final question. Can tempering to a blue/purple color affect the function or reliability of the parts? I would think with a good temper they would be appropriately hard to stand up to normal wear and not gall, but the only one that I have a real question about is the hammer which obviously you would not want to be too soft or too brittle.

Have a little while before I can fund another project but I have a good idea of what I want to do and I'm trying to finalize a direction. Thanks.

 

[Wyosmith]

Niter (Nitre) bluing is nothing more than temper bluing in a controlled and air free environment.
The salt can be controlled to within 5 degrees witch is near impossible to do with open flame. Oven bluing is basically the same, but with the surrounding air you don't get as good a color.

To get the high luster deep cobalt blue on most steel you need 620 degrees, so yes, it will effect the heat treatment on some parts. If you have a spring temper already you will be fine, but if you have parts tempered (drawn) at 400 to 550 degrees you will mess up the temper if you njitre them

 

[dakota.potts]

Will a conventional electric stovetop range hold the 600+ degree temperature desired for the deep blue with the salts? That sounds hard to believe but could definitely make the process more doable. The salts are expensive since they can only be bought 10 lbs. at a time, but I wonder if I could go into a group buy with my fellow gunsmithing students.

 

[dakota.potts]

https://www.youtube.com/watch?v=-vF3zKiUIkY

Actually, Larry Potterfield has given me a great idea. The desired temperature is very close to the melting point of lead. Perhaps a small lead pot is in my future

 

[Bill DeShivs]

If you are careful, all you need is a torch. I prefer a plumber's air/acetylene rig with a small tip. One of the hand held butane torches could work well, too. Just practice on scrap steel. Learn to play the flame on the work to achieve the color you want.
Get a firebrick or charcoal block (available from riogrande.com) to put the parts on for heating.

 

[Gunplummer]

I don't know if it is a good thing or not. I have seen tooling heat blued many times and it was not a good thing for the tool.

 

[4V50 Gary]

I think a stovetop can heat the salts. We use a propane stove at TSJC whenever we nitre-blue small objects.

Using the stovetop can also heat up the temper of the woman of the house so be warned.

 

[Wyosmith]

I use a single burner camp stove.

 

[James K]

Many of those tempering colors were originally more or less accidental, the result of heat treating springs and the like. Examples are the Krag extractor and the "straw" color ejector and other parts on the Luger. But attempting to re-color such parts by heating risks losing the tension that the heat treatment was designed to achieve. To me, unless the intent is to use the gun purely as a show piece, there is no point in "restoring" the color in an extractor if the extractor no longer works. I strongly suggest leaving those parts alone.

Jim

 

[dakota.potts]

James, all my planned projects are to use the parts solely for show pieces. Such work is encouraged by my school as experimentation and potential resume pieces. I wouldn't temper anything that holds pressure or relies on spring temper. I'm thinking about pins and screws, slide stops, safeties etc to accent a gun. The intended result is for a sporting pistol/display piece that is functional but not designed for heavy or serious use

 

[James K]

I hope there is some way to advise any future buyer that the gun was set up for show and that some parts may not be functional.

Jim

 

[dakota.potts]

No future buyer. Just a personal project.

What parts may have an issue? I see this done on triggers and safeties on 1911s and MidwayUSA has videos doing the same procedure on parts including extractor. I can see how it would affect the hammer or the trigger if the sear were attached to it, but I don't see it altering the function of simple parts like a slide stop, safety switch or magazine release. Am I wrong? Choosing a good cooling material should be able to reach an appropriate hardness without becoming too soft or brittle. I'm not talking about treating a barrel or bolt face with locking lugs

 

[Bill DeShivs]

There will be no harm done to the non-critical parts.

 

[James K]

As examples, the safety on the Luger is its own spring, as is the extractor on the Krag and on some other guns. Heating spring steel under controlled conditions, then drawing it puts in the spring (and creates the color). Heating it again without careful control ruins the heat treatment and the spring loses its tension.

Jim

 

[Gunplummer]

This is true. I have made claw extractors for Mausers and Arisakas. I believe it was Starret that used to supply a list of drawback temperatures with their O-1 tool steel. One of them was listed as "Spring". Just stating a fact. If you want to try it, go ahead. That is how you learn.

 

[dakota.potts]

I don't plan on trying it on any extractors, at least right away. I do think making springs is something I will try at some point, but as a different experiment

 

[Dixie Gunsmithing]

I don't know if I would do that to an extractor, as they're hardened, (or should be) and a wear part. To turn them dark blue, is drawing their temper into the weaker end of the spring range. An extractor should be tempered to something around what gears are, which is brown in color. You reach that before you reach the purple-blue color during tempering. Brown is around 440-500 deg F, purple around 540 deg F, and dark blue around 590 deg F. That is why heat or nitre bluing is only used for screw heads, etc.

Some have tried flame coloring double shotgun receivers, but I have never promoted that practice, as that sets up heat affected zones (HAZ) in the iron, that can cause cracking. Though the iron might not be hardenable, that was used, HAZ can still have an effect. That is why, when case hardening, a receiver has to be braced, to keep them from warping. The HAZ sets up stresses, where the heat was applied, in concentrated spots.

 

[Gunplummer]

Most iron hardens very easily. I used to harden the outside edges of machine cams by heating it with a torch and oil quenching it. A lot of cast steel is as bad or worse when you heat or weld it. It all comes back to knowing what the material content is when you go after something with heat.

 

[James K]

"Most iron hardens very easily."

I beg to doubt that, if you really mean "iron". Steel can be hardened, but iron has too much carbon to be hardened by heating. That is why some old time makers used case hardening (with or without color) on their iron frames to reduce the wear caused by the working parts. When they went to steel, many dropped the case hardening, though some (e.g., Colt) kept color case hardening for cosmetic reasons.

But heat treating is not only done to achieve hardness; in fact, overheating can produce a part that is very hard but brittle ("low number" 1903's for example), not at all a desirable result.

Jim

 

[Jim Watson]

Not a heat color effect, but there are some hardnesses of heat treatable stainless that should not be attempted. The draw temperature necessary makes the alloy brittle.
Numbers available on metal vendor websites.