Coloring screws

[Scota4570]

I am getting to that point with a Baker.   Normally I just heat them to around 900* and dunk in canola oil.  On this build I have done some fake case hardening.  I want the screws a bit flashier.  I was thinking of cooking them in charcoal at around 600*F and hoping for a deeper blue.  The charcoal would be set on top of lead in my casting pot and the temp monitored with a thermometer.   Does anyone do something along these lines? 

[45-110]

Niter bluing on a polished screw is the way to go.    Easy, traditional and cheap to do. Potassium nitrate  powder melted in a small vessel, need a thermometer for best results running at 650-700f.
kw

[Dphariss]

Polish screw to at least 600 using a drill and a somewhat padded wet or dry paper finish with 600 or finer.. Caseharden with something like Cherry Red. At least 2 reheats and dips. Reheat to cherry and quench in water. Repolish with 600 or finer. Heat shank slowly until the head starts to color then watch when bright blue quench in water. Makes for a more durable screw slot and heating to blue will avoid any chipping if the case is nice and deep. If careful you can blue the entire screw but usually the shank overheats. For lock screws and such I want nice color on both ends.
Or in a nitre bath, melted saltpeter. But this takes a lot of time but is great for larger parts and mainsprings. AND ITS MORE DANGEROUS.
Nicely done heat blue looks like this.

This rifle has 20 with the 3 escutcheons if I added it up right. I dunno how many I have done but at one point for a year or so I was doing 30-40 a week.

I have been using Cherry Red lately for a case hardening compound but I don’t think it works as well as Kasenit does I have a supply but did not want to use it on screws but I may switch back. Since I think I have lifetime supply now.

[Scota4570]

I experimented with melted potassium nitrate in the past.  It works well.  I also scares me.  A drop of water or a little bit of combustible material and I could get splattered?  I guess I should own a face shield. 

I did check around.  No retailers in my area carries stump remover in stock.  I do not know any other source of KNO3 that are off the radar screen.  Ideas? 

[ScottH]

Scota

https://www.sciencecompany.com/Potassium-Nitrate-Saltpeter-500g-Food-Grade-P16377

would this work?

[45-110]

I experimented with melted potassium nitrate in the past.  It works well.  I also scares me.  A drop of water or a little bit of combustible material and I could get splattered?  I guess I should own a face shield. 

No more dangerous than melting lead, take some normal precautions

[Daryl]

Some folks are more sensitive to possible danger than others.
There was a fellow on an air gun forum, who uses a fan to blow away the smoke from his brand new springer air rifle as he felt: "the smoke might
be dangerous, just like smoking".
My answer of "WOW! Just WOW!" got interesting remarks.
I then posted this picture. I suspect that caused him to hyperventilate.

[smoke and flames]

I just polish my heads spinning them in a drill up to 800 grit paper.  Clean with alcohol. Then holding the base of the screw with a pair of pliers I slowly heat the screw up until I see a beautiful blue heat treating color. Now quickly drop it into some room temperature or slightly warm water. Not cold water. Now you have a fire blue colored screw. Cold water will turn it black not blue.  Easy peasy

[Rwnblack]

Here are a few parts blued with salt peter. I use a Lee casting pot and I made up a PID to control temperature.

[Feltwad]

The trouble with modern case Harding is that there is too much blue the old type had a variety  such has blue, brown Yellow and green on a grey back ground
Feltwad

[xx54]

Rwnblack: What is a PID and would you please explain the process you used?

[TDM]

This is a very interesting and informative thread. Hope y’all continue to discuss it.

[bluenoser]

The PID Rwnblack referred to is a Proportional Integral Derivaitave controller.  In simple terms, is an electronic switch that turns the power to a device on and off based on input from a temperature sensing probe.  The PID can be purchased on the internet for as little as about $15.00.  The rest of the bits and pieces needed to build the unit will cost a few bucks more.  Amongst other things, they are very useful in accurately controlling the temperature in lead pots, kilns, heat treat ovens and other heating devices.  They sure beat a rheostat and thermometer.  I just finished building one for a friend's heat treat oven and the cost was about $60.00 CDN - not including the enclosure.

[Dphariss]

I just polish my heads spinning them in a drill up to 800 grit paper.  Clean with alcohol. Then holding the base of the screw with a pair of pliers I slowly heat the screw up until I see a beautiful blue heat treating color. Now quickly drop it into some room temperature or slightly warm water. Not cold water. Now you have a fire blue colored screw. Cold water will turn it black not blue.  Easy peasy

I never paid any attention to the water temp. But suspect it was usually about room temp most of the time. And I have done more of these than I could guess at. Darn now I have to try this and see. Danged curiosity anyhow. Some times I want them darker and this would be easier than reheating them after dipping in oil.

[Rwnblack]

Rwnblack: What is a PID and would you please explain the process you used?

Bluenoser is correct, I bought the parts from Ebay and it controls the temperature perfectly.  My process is simple. Heat the salt peterto 302 C, polish the part to a fairly bright polish. Dip in acetone to degrease, put the part in the salt peter until it turns a nice blue.  I dunk the part into water, then oil.  Turns out very nicely.

Here is a pic of a tank I made for longer pieces.

Rex

[bluenoser]

Rex,
Your pic got me thinking.  Would a suitably insulated bread pan work?

[Rwnblack]

Yes, definitely.  As long as it won’t leak you are set. Don’t use an aluminum one, mine is stainless but regular steel is fine.

[Rwnblack]

Here is my setup for small parts.

[Dphariss]

I prefer a hard surface on lock parts.
This was done with my gas farriers forge, Kasenit and tap water. Gives decent surface hardness no idea how deep but its deep enough to reduce wear and reduce friction. Both rifles are shooting but in final finish. Gotta do final polish etc on the pans, tune the frizzen spring on one barrel on the swivel and get the barrel colored on the Colonial.

[Blacksmoke]

Kitchen oven at 500-525 degrees for two hours then quench in ATF. and your are done! at that temp the molecules of steel open up and absorb the oil. That in turn puts a nice finish on as well as a nice blue.  However a good polish on the metal surface is required first.  Hugh Toenjes