Case hardening a Chambers Lock (decided to rust blue instead)

[Justin]

I was thinking of getting my lock case color hardened but some have suggested that will make it brittle. I have a Chambers Golden Era Flintlock that I left bright and it's a pain to get it perfectly clean after every shooting session.

I asked Jim Chambers about it and he suggested a particular company for it. However, when I contacted that place they send they wouldn't be able to make the frizzen hard enough and suggested just rust bluing or browning the whole lock.

Is it true that case hardening a steel lock will make it brittle?

[rich pierce]

Well, after the quench any part that was made of high carbon steel will be mighty brittle. You’ll need to have them temper at least the tumbler, sear, and frizzen to 450 or so or do it yourself. Plus hit the tail of the frizzen and toe area with a torch to purple or so.

So far as them not being able to make the frizzen hard enough they may be telling you that a mild steel frizzen, case hardened for a short time, is not going to bd a long term “win”. They may have gotten mild steel frizzen to Case then got complaints that it didn’t last.

[Stophel]

The lockplates, pans, bridles, and cocks are 8620, as I recall, and are a form of mild steel and they case harden nicely with no problems at all.    Heat, case, quench, and done.   I've always done frizzens with Kasenit too (though most will shriek bloody murder at quenching a frizzen in water...), but they definitely need to be properly tempered down.  Chambers/Siler tumblers and sears probably shouldn't be case hardened.

[Pukka Bundook]

The only part to case harden on one of Jim's locks is the lock plate. All other parts are ready to use as they come.
The plate is left soft as it needs drilling, tapping and sometimes engraving. Don't mess with the working parts.  they are right as you get them.
(This from Jim, years ago)
Maybe add the cock to the plate, as these are engraved as well at times.

[Mark Elliott]

I think what that company is saying is that they can't color case the frizzen to match the plate because you have to quench the frizzen at a higher temperature.   I would just harden and temper the frizzen normally and live with the color difference.  The frizzen will be mostly gray.   At least this is my take on the situation.   Also,  you could case harden the plate and cock and then polish them bright to match the frizzen.   That is what would have been done originally.   The case hardening was originally done for wear resistance.

[JPK]

I've done a number of locks and no they aren't brittle when done right. The full process has been discussed here many times. The lock plate if it has a slight bow to it can even be straightened. Having done this and still have contact with some of the people that shoot the rifles I haven’t had one fail in any manner.
Siler by Oliver Sudden, on Flickr

[Justin]

I've done a number of locks and no they aren't brittle when done right. The full process has been discussed here many times. The lock plate if it has a slight bow to it can even be straightened. Having done this and still have contact with some of the people that shoot the rifles I haven had one fail in any manner.

That's a beautiful lock. Can you point me to a good guide for this? I'm just wondering if it's doable for me.

[Stophel]

I usually polish the colors off, as I don't think they kept the colors on 200+ years ago, but I've kept them sometimes.  I've always been able to easily get fairly nice colors with plain old Kasenit, but that's not available anymore, and what I have left now might not be any good any more...










If you want colors on the frizzen, you can leave the temper colors on.

[Justin]

I ended up just rust bluing everything:





Two coats of Laurel Mountain Forge Browning Agent for 3 hours each in my 65 degree, 75% humidity basement yesterday evening.

[Mick C]

I ended up just rust bluing everything:


Two coats of Laurel Mountain Forge Browning Agent for 3 hours each in my 65 degree, 75% humidity basement yesterday evening.

I really like that finish! Nice work.   But you said said bluing above but used LMF browning.   Can you clarify?  Thanks....Mick

[smart dog]

Hi Justin,
I case harden my lock plates routinely for wear resistance, rust resistance, and occasionally colors.  I pack the plates in a mix of bone and wood charcoal and heat to around 1500 F in my oven, lower if I want colors.  After quenching I temper the plates to 490 F for 1 hour.  The biggest problem is not brittleness, which is not a problem after tempering, but the plate warping during quench. I always block my plates with a heavier steel plate to prevent that.

dave

[Anonymous]

I ended up just rust bluing everything:


Two coats of Laurel Mountain Forge Browning Agent for 3 hours each in my 65 degree, 75% humidity basement yesterday evening.

I really like that finish! Nice work.   But you said said bluing above but used LMF browning.   Can you clarify?  Thanks....Mick

LMF Browning solution is used to rust blue. Probably easiest to send you to LMF instruction page rather than try to explain. https://www.laurelmountainforge.com/barrel_brown_inst.htm

[Justin]

I ended up just rust bluing everything:


Two coats of Laurel Mountain Forge Browning Agent for 3 hours each in my 65 degree, 75% humidity basement yesterday evening.

I really like that finish! Nice work.   But you said said bluing above but used LMF browning.   Can you clarify?  Thanks....Mick

LMF Browning solution is used to rust blue. Probably easiest to send you to LMF instruction page rather than try to explain. https://www.laurelmountainforge.com/barrel_brown_inst.htm

Yep, what he/she said... LMF browning can be used to rust brown or rust blue. The finish I like the best is rust bluing which is the latter part of the instructions linked above.

[Justin]

Hi Justin,
I case harden my lock plates routinely for wear resistance, rust resistance, and occasionally colors.  I pack the plates in a mix of bone and wood charcoal and heat to around 1500 F in my oven, lower if I want colors.  After quenching I temper the plates to 490 F for 1 hour.  The biggest problem is not brittleness, which is not a problem after tempering, but the plate warping during quench. I always block my plates with a heavier steel plate to prevent that.

dave

Unfortunately, I don't have an oven that goes to 1500

[Mick C]

Thanks for the clarification and the website, guys.  I may have to give that a try......Mick

[Justin]

Here is what the rust-blued lock looks like on the rifle:







Closeup of carving on the butt (too shallow I think):


Tang carving:

[Jason C]

I'm not experienced enough to judge on the depth of the carving. All I can say is that is one dang good looking gun!

[BeanStationgunmaker]

That's a good looking rifle.Think I might do a blue finish on my next project