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.22-5-40
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Case Hardening depth on original rifles?
Dec 12th, 2013 at 8:10pm
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I admit I have done it in the past..re-cased an original rifle during restoration..But at work, while pack-hardining some parts, I got to thinking..just how much penetration of carbon..and how thick was the original case on vintage guns?  Then too, those early steels could have had almost any amount of carbon already present..adding to the case depth.  When we re-case an arm that was previously case-hardened..even if is annealed first, carbon is still in there..it doesn't go away.  By re-casing we are adding even more carbon..forcing it even deeper into the surface..and remember, it enters in on both sides of a part.  So, if we have a very thin section of reciever,,like under the barrel threads of a rolling block, or Ballard..the unhardened "core" could become extreemly thin..or perhaps non-existant,then you have a glass-hard..non yeilding section.  I once had a custom Australian cadet come back from C.C. with forge lines flowing around frame contours.  I asked if it could be re-polished & re-cased with perhaps better results?  They said they had tried this in past with Winchester 1886 recievers..and frame actually began to seperate along those lines!
   I see alot of posts glibly planning on re-casing original actions..either for looks..or in the belief it will improve strength..some assume even for modern smokeless loadings.  The danger of warpage or even outright destruction in subjecting an original action of unknown steel to high heat-treat temp. & the shock of quenching is not to be taken lightly.
  
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harry_eales
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Re: Case Hardening depth on original rifles?
Reply #1 - Dec 13th, 2013 at 1:09am
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I think that the late Oscar Gaddy published figures showing how deep the penetration of carbon was when soaking the part in the crucible for various lengths of time. If I remember correctly, the penetration was not as deep as many people thought it may have been. We are talking here or a few
thousandths of an inch. Nothing really deep.

I'll look at my files when I get back from hospital later today to see if I can find any reference to the article.

Harry
  
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Re: Case Hardening depth on original rifles?
Reply #2 - Dec 13th, 2013 at 2:37am
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.22-5-40 wrote on Dec 12th, 2013 at 8:10pm:
I admit I have done it in the past..re-cased an original rifle during restoration..But at work, while pack-hardining some parts, I got to thinking..just how much penetration of carbon..and how thick was the original case on vintage guns?  Then too, those early steels could have had almost any amount of carbon already present..adding to the case depth.  When we re-case an arm that was previously case-hardened..even if is annealed first, carbon is still in there..it doesn't go away.  By re-casing we are adding even more carbon..forcing it even deeper into the surface..and remember, it enters in on both sides of a part.  So, if we have a very thin section of reciever,,like under the barrel threads of a rolling block, or Ballard..the unhardened "core" could become extreemly thin..or perhaps non-existant,then you have a glass-hard..non yeilding section.  I once had a custom Australian cadet come back from C.C. with forge lines flowing around frame contours.  I asked if it could be re-polished & re-cased with perhaps better results?  They said they had tried this in past with Winchester 1886 recievers..and frame actually began to seperate along those lines!
   I see alot of posts glibly planning on re-casing original actions..either for looks..or in the belief it will improve strength..some assume even for modern smokeless loadings.  The danger of warpage or even outright destruction in subjecting an original action of unknown steel to high heat-treat temp. & the shock of quenching is not to be taken lightly.


Excellent thoughts!

Frank
  

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Re: Case Hardening depth on original rifles?
Reply #3 - Dec 13th, 2013 at 9:59am
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I do believe that the case from some manufacturers was deeper than others.  I've hand polished highwalls and Hepburns along with a Rem #6 without annealing and it seemed that the Remington case was much deeper than the Winchesters.  I use diamond and oil which speeds up the polishing.  I'm doing a Borchardt right now and the case on the lever is also quite deep.
I've wondered the same thing about brittleness and recasing. Parts like extractors and levers may be prone to this but have never seen or heard of one breaking because of it.  I remember that highwall coming apart a few years ago and the edges looked quite crystalline in the pictures.   Shocked Bob
  
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Re: Case Hardening depth on original rifles?
Reply #4 - Dec 13th, 2013 at 10:17am
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Interesting post, but I believe it needs some additional clarification.

First of all, if an action was initially case hardened via pack hardening from the factory then we can assume that the factory used a case hardening steel, and not a thru hardening steel for the part.

What I mean by case hardening steel is steel with less than .20 percent carbon.  I have had original Winchester 1873, 1885, 1886, 1892 and 1894 frames tested. Any reputable place doing case hardening needs to know the steel of the parts being case hardened.

It also helps if you know what steels were available during that period.  Knowing that SAE 4140 was developed in the 20s for the fledgling automotive and aviation industries, you can be fairly assured that in 1890 it wasn’t in common use.

Parts that are to be re-cased need to be properly annealed, especially very thin parts. I agree that annealing will not remove the carbon from the steel, but it will help disperse the carbon into the steel. So SAE 1018 steel with .20 percent carbon may be .201 percent carbon after being annealed, well within the safe range for re-case hardening.

The forge lines are just that forge lines, steel has a grain, and early steels had quite a few impurities.  As far as I have seen areas with forge lines are no weaker that the surrounding steel, and I have never seen steel separate along forge lines, that I would like to see.

Case hardening is not black magic,  it was very well understood 100 years ago, depth of case, bone to wood ratio, time at temp, quench temp were all well documented, and if you look at older books (pre-1940) on the subject, you will find very detailed charts/graphs laying this out.  Ie..  for xxx depth of case on xxxx steel, heat to xxxx deg for x hours, quench and temper at xxx deg for xx hours.

V/R

Mike Hunter
  

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Re: Case Hardening depth on original rifles?
Reply #5 - Dec 13th, 2013 at 12:20pm
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I was told by an experienced person,  that case hardened with bone charcoal that
you have to temper the parts after case hardening to keep them from being
too brittle.  If the person knows what he is doing there should not be a problem of
having the action too hard.  On the other hand I understand that Winchester would
reheat treat actions and blue them so they would be stronger for smokless loads.
Please correct me if I am wrong.
  
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Re: Case Hardening depth on original rifles?
Reply #6 - Dec 13th, 2013 at 4:04pm
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I have three main issues regarding CC,

1. Thin sections, like shown under the barrel thread on RB's

2. Lack of radi on internal cuts, such as the breech block mortice.

3. I've also never heard of people that do CC offering hardness or depth of hardness testing on their individule parts that they do.

I've been in aircraft work for over 30 years, including being a direct sub-contractor to Erickson Air Crane, manufactoring finished aircraft parts for them. Radi is paramount to the strength of parts under stress. Testing (MPI/Magnaflux) thoughs parts after HT is the only way to make sure that they are safe especially if you have square corners on internal cuts. Even then, w/o a radius, they'd to dangerous to put them on a aircraft.

Frank
« Last Edit: Dec 13th, 2013 at 7:00pm by frnkeore »  

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Re: Case Hardening depth on original rifles?
Reply #7 - Dec 13th, 2013 at 5:26pm
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You have to know the metal, as penetration is alloy/grade and time dependent. Metals like 8620 takes 16-hours for 0.040” whereas 1117 case hardens to a depth of ~0.045" in 8-hours (@ 1700 deg F).

Parts can grow ... typically taped holes are plugged.
  

All of my single shots shoot one tiny ragged hole with cast bullets ... it's just the following shots that tend to open up my groups Wink ...
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Re: Case Hardening depth on original rifles?
Reply #8 - Dec 13th, 2013 at 6:46pm
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Forty thou.....way too deep, most firearms are case hardened .002-.003

Just enough to provide a hard wear resistant surface.

  

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Re: Case Hardening depth on original rifles?
Reply #9 - Dec 13th, 2013 at 9:52pm
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I also would like to see any evidence of receivers coming apart at forging lines. I've seen a lot of old Marlins in either repeaters or Ballards that had forging lines or striations, and never seen one separating.
I've also had a few old guns re-cased and so far never had a problem with structural integrity. Maybe I'm not pushing the limits, or maybe the people who've done the work for me have done a good job. The people I've used do a lot of restoration with hundreds or thousands of guns cased, and never had a failure either.
Metal moving when it's heated is not unusual at these temps, and that's why many parts require blocking, or fitting of stubs to support metal during the process. If properly supported the metal wont warp or cause a problem.
  

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