Author Topic: Hot Niter Bluing of Small Parts  (Read 3220 times)

Offline AOG

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Hot Niter Bluing of Small Parts
« on: December 28, 2015, 08:02:39 PM »
Those of you who read my builds know that I like the look of blued steel on my models. I have used many cold blueing products with somewhat inconsistent results. I was talking to a friend of mine who does gun smithing about blueing and he recommended just hot blueing the parts. He told me that the Niter salts melt in the same temperature range as Lead. This post will document my attempt to use the method he recommended. Let's get started. I happened to have a unused lead pot from my muzzleloading days. So I decided to use it for this experiment.



I bought a tub of the recommended blueing salts from Brownells.



This is what the salts look like.



I poured some into the pot and started it up.



A couple of things to note here. As the salts melt the level will go down. I had to top up the pot with salts a couple of times to get to a useful depth of salts. It took about 30 min for the salts to melt and go translucent.

Next it was time to blue the parts. My friend uses the basket from an old home fryer to dip his parts. That wasn't an option for me so I used some iron wire and suspended them from a length of threaded rod.



A couple things to note. When you first dip the part salt will crystallize on it because it's cooler then the salt. Just swish it around until it's clear. That's your clue that the part is almost up to temperature. Now all you have to do is watch it. When it gets to the color you want quench the part in water. When the part is cool pull it out and spray it with water displacing oil to keep it from rusting. The finish is still soft at this point so I spray the part with gun oil and let it sit overnight to firm up. Here are the results.



Let's talk about surface prep for a moment. For a matte finish rub down the part with 200 grit paper. For a reflective finish polish the part to a shine. In both cases clean and degrease the part prior to blueing. For safety reasons make sure the part is completely dry prior to dunking into the salt. Any liquid would turn to steam and could splash hot salt on you.

PPE for this task is gloves, face shield and an apron. Do this in a well ventilated area.

I hope this is of use to some of you.

Tony


Offline zeeprogrammer

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Re: Hot Niter Bluing of Small Parts
« Reply #1 on: December 28, 2015, 08:28:25 PM »
Interesting. Thanks for that.

What was the temperature?
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
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Offline petertha

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Re: Hot Niter Bluing of Small Parts
« Reply #2 on: December 28, 2015, 08:47:59 PM »
Thanks for showing your steps. I was curious about that stuff. Can you describe what I think is your heating element. Once the blueing is done, does the salt just solidify in the container & can be re-heated & re-used?  Is (water) quenching recommended over oil for certain reasons? When the part comes out of the molten salt, does it have a thin salt coating that flakes off in the quench, or is it pretty clean at that point?

product link for others
http://www.brownells.com/gunsmith-tools-supplies/metal-prep-coloring/metal-bluing/bluing-salts/nitreblue-bluing-salts-prod1105.aspx

Offline AOG

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Re: Hot Niter Bluing of Small Parts
« Reply #3 on: December 28, 2015, 09:25:52 PM »
Zee I would love to tell you the exact temp but my thermometer maxes out at 650f and it pegged it. One of the things I have to get is a better thermometer.

Peter I was basically following a recipe. I have no idea if you can quench in oil or not. The part was hot enough on leaving the salt to not have crystals form. When you are done with the salt is will solidify into a solid mass that can be reused multiple times. The melter I am using is designed to melt lead to cast bullets. Here is a link to the manufacturer's site for details

http://leeprecision.com/magnum-melter.html

Tony

Offline b.lindsey

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Offline b.lindsey

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Re: Hot Niter Bluing of Small Parts
« Reply #5 on: December 28, 2015, 09:31:09 PM »
Sorry Tony, I was looking for links to the pots at the same time. Wasn't trying to hijack your post.

Bill

Offline sshire

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Re: Hot Niter Bluing of Small Parts
« Reply #6 on: December 28, 2015, 10:14:56 PM »
According to Brownell, the temp is 570-650f.
Best,
Stan

Online Don1966

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Re: Hot Niter Bluing of Small Parts
« Reply #7 on: December 29, 2015, 03:18:11 AM »
I hope those pots are SS steel because that salt will play havoc with it.

Don

Offline b.lindsey

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Re: Hot Niter Bluing of Small Parts
« Reply #8 on: December 29, 2015, 03:40:31 AM »
Good point Don. One of the links says aluminum so I assume that is for the pot as well.  Maybe Tony can report on that when he melts the remaining salt again. Stainless would be superior from that standpoint, but usually has a lower heat transfer rate than aluminum. These are obviously designed for lead and not salt.

Bill

Offline AOG

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Re: Hot Niter Bluing of Small Parts
« Reply #9 on: December 29, 2015, 06:14:09 AM »
On my melter the outer case is aluminum but the pot is steel of some sort. In any case the pot is available as a replacement part from Lee for $17 so it's reasonably cheap to replace if it gets too bad.

Tony