case color hardening

[marlin93]

question when a reciever is color case hardened are all the internal parts that make up a lever action given the same process or is it only the metal that shows ? thanks bill

[Jim D]

That's a good question Bill. I know that the enternal parts such as the locking lug and carrier are blued, but that doesn't mean that they weren't case hardened prior to bluing. You can do the file test on any part that you have in question to see if it has been hardened. If the file slides off the surface as you run it across, it is hardened. If it bites in, it is not. I'll try that on some of my parts and let you know.

-jim

[marlin93]

Thanks Jim a gunsmith told me that only the showing parts get the color case hardening and the rest gets blued. A new question is what was the factory bluing method for such parts ( rust bluing or another type) this is not to say the parts wern't hardened before bluing as you suggested. i'll try the file test. let me know what you find thanks bill marlin93

[Jim D]

Bill,

My personal opinion is that the blued parts were done using two different methods of heat bluing. I believe that the barrels, magazine tube and various internal parts were blued in a high temp nitre bluing process. The parts were immersed in molton Potasium Nitrate at 750F+ for a period of time. I know common wisdom is that the barrel and tube were rust blued, but I have been able to closely match the color on original Marlin barrels using the high temp nitre method. Rust bluing does not give the same color and tends to have a somewhat matt surface finish. The high temp nitre process is different than what is commonly known as nitre bluing, which produces a very bright blue and is done at a lower temperature.

But this method does NOT produce the same color that you see on early Marlin receivers. I have started experimenting with charcoal bluing where the parts are placed in a rotating drum with bone charcoal and other ingrediants at 730F for four hours. In my opinion this method reproduces the rich deep mirror finish black color that you see on early mint Marlins.

My opinions are base solely on the results that I have achieved, and not on any research. I may do a post on the charcoal bluing process here in the near future.

-jim

[marlin93]

very interesting your experiments produced some valuable results. i'll try and find out the process marlin used back in the day. i would like to do what your set up for with the trial and error. let me know if you ever post anything more on the subject.

[marlin93]

turnbull restoration says marlin used rust blue as their process. can anyone dispute this? I also would have thought bone charcoal would look more original.

[Jim D]

I respectfully disagree. See my earlier post.

-jim

[Jim D]

What exactly are you asking? Are you asking if the receiver was blued or color case hardened? Or are you asking how the blued parts were blued?

-jim

[marlin93]

thanks jim for reply. i was just reading some of your posts and admiring your beautifull restorations .Your the man that is for sure. i was wondering what blueing process marlin used for barrels and small parts only when 1893's were being made.

[marlin93]

jim i just re-read your earlier post which explains everything to a t. i'm a little mystified why rust blueing wont yeld the same results as a original if that is actually how marlin did it. you are a world of knoweledge to me and appreciate your answers. i am new to guns but skilled in the trades and find restoring and proccesses of these marlin rifles alot of fun. i am begining to work on one now. i am going threw all the old posts to learn all i can .

[Jim D]

Marlin93,

Everyone will tell you that Marlin rust blued their barrels, and maybe they did. But, rust bluing is a VERY labor intensive process, and it works by RUSTING the metal. In other words, pitting the metal. Rust blued surfaces are dull because of this. Rust bluing creates a black color instead of a blue/black color. I have several near mint Marlins, a couple of 1881's and a couple of 1893's. The barrel color is blue/black, and it is shiney, not dull.

If I was a production manager for Marlin back in the late 1800's, I sure would have found a way, other than rust bluing, to blue the barrels and magazine tubes. I have rust blued a number of Marlin barrels using several different rust bluing products, and nothing comes close to the original factory bluing. In my opinion, the high temp nitre process is dead on for both color and finish. Plus it is so much easier of a process than rust bluing. Small parts were heat blued. So there you have it, everything I know and then some!

-jim

[Jim D]

Bill,

Here is an example of three different finishes on an 1889 Deluxe that I recently completed:

The lever and hammer are color case hardened using the original bone/wood charcoal case hardening process.
The barrel, loading lever and screws are blued using the high temp nitre bluing process.
The receiver and bolt are blued using the charcoal bluing process.

Note the difference in color of the bluing between the barrel and loading gate vs the receiver and bolt. Both are a heat bluing process, but both produce different colors. The barrel and gate are a blue/black whereas the receiver is jet black. If you go look at mint Marlins from this era, that is what you will see. Did Marlin use a different process than I did? Maybe, but if they did, I don't know what they are. Rust bluing would certainly not produce the mirror black finish on the receiver. Keep in mind that there were just two basic methods of bluing steel back then; rust bluing and heat bluing. Hot salt bluing wasn't developed until sometime in the 1930's.

Hope this helps.
-jim

[marlin93]

WOW--thanks jim for the imformation and photo. perfect example . i will never have a rifle rust blued now . i really perfer the jet black look. are all internal parts such as the carrier treated the same way?

[Jim D]

Bill,

The internal parts would have been heat blued- probably the high temp nitre blue. Just like the barrel and loading gate on this rifle.

-jim

[marlinman93]

Jim,
Your latest charcoal blue seems to be as close to original as I think one can get. It seems like most the restoration work I see nowadays looks just too grayish with rust blued barrels and receivers. People have seen this restoration color so long now that they accept it as correct, without ever comparing it to what Marlin bluing looks like.-Vall