color case question

[smart dog]

Hi Folks,
Jim Kibler asked the logical question of why we don't find 18th century guns with evidence of colors on the case-hardened locks if leaving the tints was a common practice, something I inferred from Frankland's quote.  I certainly have not personally seen any 18th century guns with color case-hardened locks but I may have found an example shown on the auction website:

http://morphyauctions.auctionflex.com/showlot.ap?co=31120&weid=21695&weiid=7909819&archive=n&lso=lotnumasc&pagenum=18&lang=En#images

Click on the site and scroll down to the Mortimer dueling pistols.  The auctioneers badly misdated the guns.  I suspect they really don't know much about them.  The name H. W. Mortimer and Co. on the barrel indicates they were made before 1806 and probably during the 1790s.  Obviously, they were converted to percussion.  The locks certainly seem to me to show case colors.  See what you think.  They are beautiful pistols.

dave

[Jim Kibler]

Thanks Dave.  Those are some beautiful pistols.  Do you think the locks surfaces would have been disturbed when converting to percussion?  Wonder if they would have been refinished in the process?  The case colors may indeed be first work, but just considering possibilities.  One interesting thing, is how much the colors seem to have faded over time.  Good stuff.  Seems the auction estimate was off a bit, huh!

Jim

[smart dog]

Hi Jim,
Yes, it is certainly possible they were heat treated during conversion.  The feather spring holes are filled on both so heat probably was applied.  It is an excellent conversion job.  I guess the question would be if the gunsmith tried to maintain or match the original colors on the locks or did the owner want him to introduce color tints rather than keep a bright polish or bluing.   It is interesting how much the colors have faded, which suggests that colors on guns made earlier than these pistols may simply have faded away.  Perhaps, prior to the mid 19th century, gunsmiths like Bailes did nothing to actually enhance and preserve colors.  They simply left them as a pleasant consequence of a cost-cutting measure (not polishing them off) and then turned the result into a fashion.  You know in the old days of software development we used to say "that's a feature not a bug". 

Take care,

dave

dave   

[James Rogers]

While I am currently not able to cite scripture and verse documentation, I would think it possible that for the time frame of these guns, the case may be original. Again, by this time I do not think it was standard but was emerging as accepted  with the likes of Mortimer, etc.
This may very well be why Frankland, in this same time period mentioned Bailes as an early pioneer to introduce the acceptance, and not the discovery.
Twigg went away in this time frame and I do not remember anything of his manufacture suggesting colors but possible. Of course the possibility during conversion is high probability as well.
There is only scant information on this and it is certainly interesting sorting thru the clues.

[Dphariss]

I think he was just trying to find out marlin did their colors and trying to duplicate the process to do restorations.


Dan,  IS there any diff between bone charcoal and cyanide-added processes in terms durability, depth of harness, and fade resistance?

I am not sure about all the factors in "hard" but a case hardened part is a case hardened part. As to depth of case I think that cyanide is faster than charcoal since the parts are put in a hot pot rather than having to pack a container and heat is all up to temp.  Cyanide will not give the right colors for most 19th century guns but it will produce more parts per day with less equipment and fewer people  than a similar level of production with charcoal will. As previously states its more fool proof.
So far as I know the colors are all very thin and are not "hard" they are just an oxide on the metals surface. It is all to easy to damage or remove colors made by either process. But a soft scraper, for example, will not damage the colors when stocking a hardened action if reasonable care is used. When necessary I could shape to a hardened action with a soft spring temper  scraper. Then remove the metal from the wood for sanding.
Case depths over .005-006" are not needed but I need to have a conversation with an expert to get the final word on this. I am pretty sure that the low temp casehardening is not going to produce as good a case as higher temps will especially so far as  depth of case.

Dan

I talked to an expert today and he said that its practically impossible to get .020" case depth.
The carbon tries to migrate to parts with little or no carbon. However, as the carbon builds up its increasingly difficult to get the depth deeper. The carbon in the surface layer, perhaps .008 deep when quenched, actually slows or even prevents more carbon from entering the iron/steel.
He stated that the only way he could see to get .020 deep case would have been at 1600+ degrees and perhaps coal dust for carbon rather than charcoal.

Dan

[Jim Kibler]

I'm sorry Dan, but you might want to reevaluate the title you've given to your friend.  Why do we need these titles (expert, master, masterpiece etc. ) anyway?  Yes, carburizing is a process of diminishing returns.  From a simple perspective it is a diffusion controlled process, but in reality surface interface reactions make it somewhat more complex.  Here is a chart from a manufacturing company that provides estimates of case depth versus carburizing temperature and time.



Now, I can also assure you that .020" case is absolutely no problem to achieve from personal experience.  My personal experience goes something like this.  Received a metallurgical engineering degree from OSU in 1997.  From around 2005 - 2009 I worked for a company that produced and carburized large numbers of parts for the automotive industry.  Evaluating and measuring case depth was common procedure.  Case depths greater than .020" were easily obtained on a regular basis.  On to gunbuilding....  After no longer having the use of this companies carburizing facilities, I bought equipment and began doing this work on locks myself.  Yes, I have produced cases well in excess of .020", particularly on frizzens.  Yes, I have run test parts and checked depths obtained. 

This may seem a little terse, but frustration can tend to build when a message is repeatedly ignored.

[Jim Kibler]

How do you think blister steel was made?  It certainly wasn't made with .020" case depths.  Yes high temperatures were used, but a simple .020" is obtainable with reasonable temperatures.  Point is, .020" is not "practically imposible".

[Roger Fisher]

Baked in charcoal from the bones of Whooping Cranes and Spotted Owls, quenched in the tears of virgins; that produces the best case hardening.

Ok I'll be the bad guy..... W. Cranes and spotted Owls easy to find; but the virgins

[Jim Kibler]

Especially in your neck of the woods Roger

[Dphariss]

How do you think blister steel was made?  It certainly wasn't made with .020" case depths.  Yes high temperatures were used, but a simple .020" is obtainable with reasonable temperatures.  Point is, .020" is not "practically impossible".

Oh brother.  
CONTEXT people context.
Could we possibly confine out discussion to GUN PARTS and CHARCOAL process? With enough time and temp KASENITE will give deep penetration too.

So tell me. What process do they use to get these case depths? Is it a charcoal? This is the context of the conversation, we are not building large mining equipment after all. Do the parts come out with colors or without?
I am not talking of large diameter shafts or huge gears or other industrial or automotive parts that are hardened then perhaps ground to final tolerance  AFTER they are hardened.

I know that some automotive crankshafts, for example, have hardness depths over .010 and can be reground to -.010 and maintain their wear surface. But these are not processed as a casehardened lock would be in 1780. So I see no point in bringing forged alloy crankshafts into a discussion of packhardened gun parts. What would be the point?

Blister steel. I know about blister steel. I just don't connect making blister steel with color casehardening.
Practically impossible in the context of color casehardening with charcoal and expecting proper colors.
CONTEXT OF THE CONVERSATION.
If we change the context every post then almost anything is possible.
If we insist on including modern methods and materials or things such as making blister steel then we could include nuclear fusion I suppose.
The guy I talked to has done several runs a week for 15 years or more.  I know the Peabody action I pictured in another post was done probably 15 years ago. He does several heats a week. He was watching the furnace when I was talking to him. He does hardening all the time PROFESSIONALLY. But again the CONTEXT of my conversation was pack hardened gun parts not gears for a Bucyrus-Erie.


He said that very high temps, over 1600, would be required and a pack other than charcoal would probably be needed to put deeper case on parts. I posted that.  
Then we have to ask WHAT IS THE POINT? If both parts are equally hard there will be almost no wear at all in OUR CONTEXT.
Where firearms parts are concerned heavy cases are simply not needed. In thin section parts its a serious DETRIMENT. Why? THEY BREAK unless well annealed. If annealed past about 450-500 f  they are less "slick" when bearing on other parts. The color is maybe changed if the parts are color hardened.
IIRC these parts that you have seen with .020 case depths WERE BROKEN... THEY BROKE. Does this not tell us something?

Casehardened parts are not supposed to break this is one of their advantages. A hard, even brittle, wear surface and a tough core. They should bend and maybe crack the case, not snap off. I wish someone would show me some reason why a flint cock or a lock plate or a sear or tumbler needs .020 case depth. There is no reason. Unless we want it to BREAK or chip.
So why don't you fire up your charcoal casehardening process and color caseharden a part .020 deep, with no surface damage, send it to a lab and have it tested then come back and tell us all about it.

If anyone thinks that .005-.008 case depth is inadequate. I suggest they have something casehardened to this depth then try to reshape it with a mill file....

Dan

[DB]

All this talk of case hardening and color case has my head spinning
I will ask something simple. Locks straight off the shelf such as Chambers or L&R, do they need hardening or just polishing?

[smart dog]

Hi DB,
All the internal parts, frizzen and springs are hardened and tempered on Chamber's locks so you don't have to do any heat treating, just polishing (or browning, blueing etc).  However, I harden and temper all of the lockplates and flintcocks on my locks after I engrave them.  It is not necessary but I like the extra rust resistance of hardened steel. 

dave

[Jim Kibler]

I talked to an expert today and he said that its practically impossible to get .020" case depth.
The carbon tries to migrate to parts with little or no carbon. However, as the carbon builds up its increasingly difficult to get the depth deeper. The carbon in the surface layer, perhaps .008 deep when quenched, actually slows or even prevents more carbon from entering the iron/steel.
He stated that the only way he could see to get .020 deep case would have been at 1600+ degrees and perhaps coal dust for carbon rather than charcoal.

Dan

I will repeat once again then you'll probably be glad to hear that I will give up.  This should address some of your sugestions.

Case depths over .020 are easily obtained with a charcoal pack.
This includes gun parts.
Frizzens in particular should be at least this deep and preferably deeper to perform well over a large number of shots.
I have pack hardened frizzens using processes that produce depths well in excess of .020"
Reference the previously included chart to estimate times needed at given temperatures.
I have verified the resultant depths
As a metallurgist, I understand the process of determining case depth.
Coal dust is not necessary to obtain these depths.
Please read the previous post included above.
Please identify what I am taking out of context.
The more that is written does not make an arguement any more convincing.

The End

[FL-Flintlock]

As a metallurgist, I understand the process of determining case depth.

I'll bet your secret mojo is quenching in Danish oil.  

One can also vary the depth per hold time and temperature with the addition of proteinaceous materials, NaHCO3 and/or CaCO3 proportional to the charcoal mass ... but, perhaps, one could find an "expert" to claim that Stoltzer's method of producing 0.030" deep case in 90 minutes @ 1600°F doesn't work despite it being used for almost a century.  

[Dphariss]

I talked to an expert today and he said that its practically impossible to get .020" case depth.
The carbon tries to migrate to parts with little or no carbon. However, as the carbon builds up its increasingly difficult to get the depth deeper. The carbon in the surface layer, perhaps .008 deep when quenched, actually slows or even prevents more carbon from entering the iron/steel.
He stated that the only way he could see to get .020 deep case would have been at 1600+ degrees and perhaps coal dust for carbon rather than charcoal.

Dan

I will repeat once again then you'll probably be glad to hear that I will give up.  This should address some of your sugestions.

Case depths over .020 are easily obtained with a charcoal pack.
This includes gun parts.
Frizzens in particular should be at least this deep and preferably deeper to perform well over a large number of shots.
I have pack hardened frizzens using processes that produce depths well in excess of .020"
Reference the previously included chart to estimate times needed at given temperatures.
I have verified the resultant depths
As a metallurgist, I understand the process of determining case depth.
Coal dust is not necessary to obtain these depths.
Please read the previous post included above.
Please identify what I am taking out of context.
The more that is written does not make an arguement any more convincing.

The End

I ask why cocks need to be cased .020+ deep and you switch to frizzens. This is not a straight answer its an evasion.

Did your process giving .020+ penetration produce  colors?  Getting deep penetration, as was noted, requires higher temps, over 1600, than is done for color hardening.We need to not here that the expert I talked to does COLOR CASEHARDENED firearms parts. This from what I know, limits the temp to UNDER 1600, deeper penetration means higher temps and generally NO COLOR. So if the deeper cases need 1650-1750 its not something he is likely to do when he gets paid for COLORS and usable case depths, he says .008". In doing a little research I see that most modern casehardening is done at higher temps, ranges that will reduce or eliminate the color or though a process that is not intended to or cannot produce colors. In the shop Tues. we were discussing COLOR CASEHARDENING with bone and wood charcoal. Its not the same as casehardening parts where deep penetration is desired, or doing parts like self-tapping screws that will be plated anyway.

And again, why do lock parts need to be cased .020" and don't jump over to frizzens again. I have pointed out that thin section parts with deep cases, in the case of a broken neck on a cock perhaps not all THAT thin, tend to break. Threads can chip off at the edge of holes even with cases less than 1/2 of .020, threads chip off screws, screw slots chip. 1/2 cocks are bad to break too the thinnest section can snap right off with little or no "provocation". Sear noses can break off.  Lots of bad things can happen and I have seen most of it at one time or another.
So why does a lock plate, a cock, a bridle, a sear or a tumbler need to be cased .020+ deep. I contend that the .020 or perhaps greater depth on the flint cock you found broken is a classic example of a part being cased so deep as to becomes UNRELIABLE.
Where is the advantage in making the parts so brittle that they break?


Then we have the question of how high was the temp used to caseharden gun parts in the 18th century and did they use a temperature range that would have eliminated color being produced consistently? If so this would explain the lack of colors on casehardened parts and why they polished the parts. This alone could be why colors were not common. It was difficult to hold the right temperature? Did they intentionally harden the parts deep to give a deep case to the frizzen face? This could explain parts breaking from excessively deep cases.

However, if the pack is done right with the right mix of charcoal ect and the temp is 1500 or so then color usually results even with plain water.
Which my friend never changes BTW. He just adds more as it evaporates and cleans out the charcoal etc when needed.

Dan

[FlintFan]

I ask why cocks need to be cased .020+ deep and you switch to frizzens. This is not a straight answer its an evasion.

I don't think anyone ever said cocks need to be cased .020+.  I think the reason frizzens are brought up, is because the depth of the case on that specific part is critical to the function and wear of the lock.  A more shallow case on the other parts is easily achieved and preferable.  I case harden my frizzens separate from the other lock parts at a higher temp and longer soak.  I have found warpage on frizzens to be very minimal, and the colors produced at the higher temps are a very close match to what I get on the other lock parts.  

[Jim Kibler]

Oh, I can't help it.  I'll add a bit more.  You're right Dan, cocks, plates don't need to be cased to .020".  Frizzens do.  Please read your original post which I took issue with.  Nothing was specific to cocks or frizzens.  Further, there are steps that could be taken to get .020 plus case and still have colors.  The most obvious is to run a cycle at higher temperatures with longer hold times, let the parts slowly cool in the pack, touch the polish up and then re-run using typical low temperature color case cycles.  Another option that might work fine is to carburize at a higher temperature then simply drop the temperature prior to quench.  Might work, might not.  Point is I'm confident colors could be obtained with a .020" plus case.  A simple higher temperature and longer hold time process may not yield colors, but I never care about them anyway.  Think they look sort of dumb on 18th century guns.  Nothing more than a personal opinion of course  Enough said AGAIN.  Thankfully going out of town soon.  Hopefully no internet access will be available

Flintfan, thanks for your reason and sharing your experiences.