Every so often I read where someone has a shotgun frame that's come back warped after being re-cased. The barrels will no longer fit. The gent starts a thread on one of the websites and asks how to correct the problem. And in reply people will pipe in and say... too bad... sorry but you goofed up by not having the frame annealed before the re-casing.

Although I'm not a metallurgist myself I know that heating steel to a red hot state (as is done in case hardening) will make it softer and relieve internal stresses. Interesting.... because that's the definition of annealing.

What I'm saying is the steel is annealed in the first part of the normal case hardening process, then it's quenched. So, is there any reason to anneal the frame in a separate step before the case hardening is done? Isn't that redundant?

I'm beginning to think the separate annealing step is nothing more than a theory/excuse/BS for a problem that isn't understood very well.

What am I missing here? Thoughts anyone? Thank you. Silvers

I sort of see what you're getting at except that to get a dead soft condition as a final result, controlled rate of cooling in a furnace would be part of the definition of annealing. How about blocking and fixturing of the frame before it's in the pack? Didn't O. G. resort to that? How much does that contribute to restraining distortion? Do the usual suspects in recasing take that precaution?

jack

Silvers,
Somewhere I'd read the same - anneal before re-case - even if you're not engraving.

I asked the guys at Classic Guns about this exact thing... and heard a couple seconds of dead air while John suffered another ding-a-ling question from a tirekicker. He politely said he didn't find annealing beforehand added any extra measure of protection against warpage. He would anneal first for $25 if I insisted, and then clearly reiterated his position.

It seems to me that if one wishes to polish the metal to perfection before hardening, it is necessary to anneal. Certain it is the case where any engraving work is anticipated. Perhaps I am in error and am more than willing to stand corrected.
Best,
John

All firearms that are to be engraved are first annealed. This certainly makes polishing much faster and easier. John always anneals firearms intrusted to me before I start work. he blocks and braces the action & side plates when present when doing this service. After engraving, he blocks and braces same piece when color casing --- after many years of using his service I haven't had a warped frame come back. FWIW, Ken

I thought you guys would have figured out by now that re-case coloring SxS's is a bad bet.

I'll have to take some pics of the two actions that just came back from John Gillette. I dont mind the odds really if the guy doing the work knows what hes doing, and John does. One of the actions sports a bit o scratchin from Mr. Ken, looks Ok to my eye.
Steve

Yeti,
I think if you really pushed John for a definitive answer he would say "anneal the frame". I was at John's shop for a few minutes today and we discussed the very same issue. He would very much prefer to anneal the frame before re-case. I also remember having the very same discussion with Oscar. Oscar would not recase a frame unless he annealed it first to relieve stress in the steel.

Recoil Rob:
I think it depends on who is doing the work.
I would not trust most, but have and will trust a man that has a proven track record.
And speaking of records, let us make the record a correct one. Case coloring is the result of case hardening by heat and quenching. OR, and the OR in large letters, a chemical process such as cyanide where hardening by heat and quenching is not done.
Best,
John

Thanks everyone who replied so far. Just to clarify, I was asking about re-casing without doing any engraving. Also I was referring to the bone charcoal/quenching process of re-casing, not the cyanide process. Silvers

Color casehardening is a carburizing process wherein carbon is introduced to the outer layers of the steel in order to harden the skin of the part. In this process the carbon is pulled from the charcoal pack via heat and is trapped by the subsequent quench. Carbon must be present in order for steel to harden.

To properly "re-case" a part, the previous hardening process must be "undone" via the controlled annealing process. I used to
work in a very well known shop that specializes in casehardening and we NEVER re-cased a part w/o first annealing it.

Warpage in my experience relates more to the design of the action, trigger plate, etc. L.C. Smiths, Parker's and others rarely had warpage issues because the frames and other parts were thick where they needed to be and could usually be reassembled w/o hard fitting. Every Ithaca Flues that I have
re-cased required hard fitting. The tangs and trigger plates on the Flues always move because they are thin and just tend to warp due to the heat. It just takes a little time and experience to hard fit re-cased parts back to where they need to be for final assembly.

Dan May

I don't know if Wind River annealed or not, but I think the colors are nice.

I'll agree with you John, that a man with a proven track record has a better success ratio than others but even the best can have one turn out bad. They're probably just better at bangin' the thing back into shape.

They had to whacked into shape the first time they were done. Read crossedchisles article in SHOTGUN TECHNICANA about the PROTOCOL AT PURDEY'S. It was the finishers first task to stress relieve and true up all the metal that had warped in the hardening process. Now there's a guy with a good resume', and even he screwed up at times and it was his full time job. It's one thing to damage a part before the gun reaches the owner, you can make another, but what about your 1907 Fox? Are you going to be happy if he breaks the top tang and has to weld it?

I think it's a gamble with a SxS because of the critical geometries involved with the barrel fit, too much of a gamble for a vanity exercise.

Old Highwalls, Sharpes and slab sided lever actions? Have at it, not too much to mess up there. But my old SxS's will age gracefully.

Just curious, do the re-case color guys have you sign a waiver before they'll cook your action?

Just to set the record straight, Cyanide "Hardening" is not a chemical process but a carburizing process as is the charcoal method. It is used when a very thin case is satisfactory & operates by immersion of the part in molten Sodium Cyanide at temps on the order of 1450°-1650°F. The metal absorbs a thin carbon rich "Skin" which is hardened upon quenching with the colors formed by oxidation. One might say, "It is the same, but different" as Charcoal hardening. Cyanide hardening is I believe quicker & generally less expensive than "Pack Hardening" (Charcoal) but normally does not give as deep a case & colors which in the eyes of many are not as attractive.
Ref; "Machinery's Handbook" (not a direct quote)

Doug Mann,
Thanks for that info. I've been hesitating to color the gun because 2 folks here have dealt with post CCH warpage. Now I'm sure I'll blue it.


Edit: My question to Classic was regarding a previously blued reciever...not re-casing.

Miller,

Thanks for that last post. It should also be remembered that for some guns, it is the correct method. Cyanide case colors have their own appeal.

Pete

It should also be noted that parts can be recolored without rehardening. The temperature range wherin oxide colors form is well below the kind of temperatures likely to warp metal. Dr. OG recommended doing this. Note that most of the colors in CC are within the range of iron oxide colors, but some depend on other stuff such as is found in the bone charcoal. Masters of the process can control to a significant extent the pattern (sttripes/spots/mottled) and the predonimance of color (mostly blue/mostly brown/a dash of green/almost grey/etc). Usually, one wishes for the master to recreate what was originally on the gun.

I would reccomend annealing before CC'ing. And no, it does not do the same thing when you heat the action up in the CC'ing process.

I remember reading somewhere that if metal washers and/or various bits and pieces of metal are wired to portions of the item to be color case hardened (bone and charcoal method)that the case coloring patterns can be controlled and duplicated. Is anyone familiar with this? I think that this is practiced in the U.K.

Oscar would not recase without annealing first. The hundreds of actions he did had no distortion problems and did not crack later.
bill

John Gillette of Classic Guns studied under Oscar & does the same process that Oscar taught him. In 8 years, I have never had anything but great work from John using Oscars methods. FWIW, Ken

Sounds like a good idea to me. From what I've read about casehardening both guns and industrial, timming is critical. The longer you leave the part in the carbon the deeper into the steel the carbon absorbs. You could make your part high carbon steel and brittle. Recasing without an anneal would be like doubling the time in the carbon soak. Remember the cracked frames we saw on here awhile back? That nice Stirlingworth? I once annealed a LC Smith frame in the oven on the clean cycle. It works and the steel was soft so I could file and polish it.

Silvers,

Does the action need to be polished at all? I think John Mann and Ken Hurst are on point on this. By annealing the action first, you have the opportunity to easily remove pits, dings, etc. If the action requires any prep work, I don't think you'd go without annealing it first.

Even if you don't, i think you need to ensure a controlled hardening (feel free to insert viagra joke here....) and to do that, you likely need a controlled and homogeneous softening....

Just my opinion.

FYI. John recently annealed, colored/ hardened my beretta action on my Ken Hurst sporting gun. It didn't warp........

Phone number for John G? I want to talk to him about this issue.

From my experience (not hypothetical) warpage can take place whenever the metal is heated above the "critical temperature". I've seen it in old metal that was pre-anealed and in metal that had never been hardened. I'm talking double shotgun and single shot rifle actions, lockplates, trigger plates, forend irons, triggers etc.
Casehardening without the likelyhood and readyness to "hard-fit" after the fact is wishful thinking. Many jobs don't require it, but you had better be ready for some serious "tweaking" if warpage occurs. Straightening is not recommended for the inexperienced or heavy handed. The "hard-fitter" was once a job title for maker's of new guns.

Classic Guns
PO BOX 367
606 GOULD STREET
BEECHER, IL. 60401
708-946-6141
http://www.classicgunsinc.com/

John with his pal, Lucky.



Pete

Thanks all who replied. There's a wide range of fact and opinions here. What I've concluded so far is:

1. The need for annealing before re-casing (if you're not going to do engraving first) is still with the jury.

2. Old metal parts sometimes warp when re-cased, sometimes they don't warp. If you get something re-cased you might have problems reassembling the parts. Think about this if you plan to do the disassembly yourself and send the stripped parts to a re-casing service. Discuss with the service beforehand and ask them about warping.
Silvers

SDH is right on, time and temperature is critical. Knowing when to stop the process and just how far it needs to go with a certain type of gun is what separates those who can from those
who "warp".

But as stated earlier, there are some guns that are more
susceptible to movement than others. Use an experienced hardener
that has done your kind of gun in the past (hopefully many times)
and discuss the possibility of movement. Then you can make
an informed decision.

DM

Silvers, anneal the piece before re-casing it ! Ken

Silvers,
Respectfully suggest you obtain and read Oscar Gaddy's seminal works on the subject in DGJ. Further I was trained by Pete Erdner at Piedmont CC. Pete has done thousands over the course of 20 some years as the "Professor". He would not consider re color casing anything unless it was first annealed. This even included Crescent Arms single shots. Indeed his most noteworthy observation is that "good steel is the basis of good case color." Good luck, Dr. BILL

Just got off the phone with John G. We spoke of both the metallurgical and practical aspects of case hardening and coloring. The gist is as follows.

Metallurgically, annealing before re-case hardening is not necessary. All hardness is lost when the metal temperature goes above critical; the metal has no "memory" of hardness. Practically, most parts will require some amount of polishing/pit removal/re-engraving which will be vastly easier to do after annealing. Further, a part retaining the original "skin" hardness is more likely to be filed/ground/polished in a way that leaves the "skin" thickness uneven - remember that case thickness is on the order of 0.002" - 0.003". Re-casing will increase the "skin" thickness and surface carbon content. But, it will not completely even out the thickness. Thinner parts are more likely to warp from an uneven "skin" thickness.

Warped parts can generally be bent back to working dimensions due to the core softness of the metal and the thinness of the hard "skin".

Repeated case hardening cycles will produce poorer colors due to increasing carbon content at the surface (high carbon steel is more resistant to oxidation than is low carbon) and thicker "skins" that are more prone to warping and to cracking. Smaller/thinner parts are more subject to this than are bigger/thicker parts.

Modern alloys can generally be case hardened without through hardening due to the higher critical temperature of such alloys. Also, those parts that are through hardened can be case hardened and colored without loss of all through hardness as case hardening/coloring temperature is around 1250 degrees F.

Oxide colors can be restablished at temperatures in the 700 degree F range. John tells me that some of the CC colors do not appear in oxide coloring and will be absent unless the part is heated to the afore mentioned 1250 degree range and submersed in casing material. He should know better than I do.

In sum, most parts will need to be annealed prior to re-casing. Warping is a fact of life and not the end of life. There is a very finite number of times a part can be re-cased; for very thin pieces that may be only one (the original). Oxide colors can be re-established without rehardening, but true CC can only be re-established via re-casing.

Hope that helps some.

I have a good friend that has reestablished colors on perhaps 20 double guns at his home workshop using bone charcoal pack, quenching in highly oxygenated water after heating to around 650 degrees in his heat treating oven. His colors are very nice and do not look cheap or tacky. They may lack some of the colors that are possible to achieve at the 1200+ degree range. My question is, can variation of the pack materials help achieve some of those colors at low temps that are normally brought out at the higher temps, or is it only possible to get those colors by going to the higher temps? If so, why risk the higher temps if polishing or chasing of engraving is absolutely not necessary?

Stan

Stan et al:
Perhaps this will be of interest.
I have mentioned this before but will mention again.
About three years ago I have the great pleasure to examine a beautiful gun that was custom built in the Tula (USSR) Arsenal. It had bee a presentation piece from Kruschev to Wilson.
This gun had the most incredible colors. It was pink, reddish, orange, green, blue and light purple. The overall tints were subtle and astounding beautiful. Much like the most lovely sky just before the sun sets.
I posted the question of how these colors were gained and our friend, Geno answered. He stated that is one used powdered leather charcoal as well as bone, this was the result.
I think that the reason that I was so smitten with these subtle colors is that they did not camouflage the the beautiful engraving as does deep colors.
perhaps we can encourage some to try this. I think I may with the Pedersen at some time.
Best,
John

Thanks Rocketman.

Yes, this one has been just a bit more revealing than our 1001 previous disputations over Martensite and the critical temp. For me, it's a keeper. And thanks to John Gillette also.

jack