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Forums10
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Apr 29th, 2024
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Joined: May 2003
Posts: 264 Likes: 23
Sidelock
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Sidelock
Joined: May 2003
Posts: 264 Likes: 23 |
I have in my shop a Greener FH35 that appears to have escaped the hardening process entirely. Either that or every part of it was annealed and left soft. The gun has obviously given years of good service and is still mechanically sound. Unfortunately all the engraved surfaces are worn down to the point of being barely discern able. Action, fore end iron, trigger plate top lever Deeley latch, trigger guard. It seems none the worse for wear but this seems to reinforce the argument that Hardening was more to protect the aesthetics rather than contribute strength.
Any budding engravers need a project??
Hugh Lomas,
H.G.Lomas Gunmakers Inc.
920 876 3745
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Joined: Feb 2009
Posts: 7,464 Likes: 212
Sidelock
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Sidelock
Joined: Feb 2009
Posts: 7,464 Likes: 212 |
OK, lets do a wee bit of metalurgy. Anyone with differing information is most welcome to step right into this. I'm not nterested in being right, rather that we all know the truth.
...if I made two identical springs from "soft" and "hard" steel, they would behave almost identically as springs until the "soft" one was deflected beyond its yield point. The "soft" one would now be permanently bent (dimensions altered) while the hard one would return to original dimensions.... Just for conversation, if identical in every way except for hardness, I believe that what ever point you compressed the soft spring to make it yield, that will also be the same point that the hardened spring yields. The hardened spring may require more force to get to that same deflection point, but that amount of deflection to permanent deformation will be the same for both springs. Probably, identical leaf springs would be a better example because a coil may compress to solid without yielding. I believe receivers have been shown to spring when a gun is fired, but it seems to be related to design and the nature of the iron/very mild steel and not heat treatment to spring characteristics. We may be thinking along similar lines.
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Joined: Feb 2004
Posts: 13,880 Likes: 16
Sidelock
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Sidelock
Joined: Feb 2004
Posts: 13,880 Likes: 16 |
[quote=craigd Just for conversation, if identical in every way except for hardness, I believe that what ever point you compressed the soft spring to make it yield, that will also be the same point that the hardened spring yields. The hardened spring may require more force to get to that same deflection point, but that amount of deflection to permanent deformation will be the same for both springs. Probably, identical leaf springs would be a better example because a coil may compress to solid without yielding. [/quote]
Craig
your understanding is incorrect. Steel has a Young's modulus that is unchanged by heat treat.
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Joined: Jul 2005
Posts: 7,065
Sidelock
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Sidelock
Joined: Jul 2005
Posts: 7,065 |
The case hardening increases the yield strength. I agree that modulus of elasticity changes little.
But it is the yield strength that determines whether the frame bends or springs.
I am glad to be here.
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Joined: May 2008
Posts: 8,158 Likes: 114
Sidelock
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Sidelock
Joined: May 2008
Posts: 8,158 Likes: 114 |
The case, as mentioned, is very thin and contributes little, if anything useful, to deflection strength.
DDA Well, as I try to remember where I got that information, the skin aluminum on a monocoque fuselage is very thin in relation to the cross section of the fuselage but adds tremendous resistance to both torquing and bending of the fuselage. I remember when I read the article that that was the conclusion that I came to. And apparently the low carbon frame doesn't need much stiffening as the Winchester 21 action steel is only about double strength of the low carbon steel but doesn't require case hardening. I wonder what the difference in hardness is between the 21 steel and unhardened low carbon steel? I bring this up because of the contention that receivers are case hardened primarily to resist wear, say between the knuckle and the iron, which of course should be lubricated and have no wear. Double fitted 1018 case hardened American doubles- not quite the same as the single (hard) fitted M21 made of AISI 4140 nickel chromium molybdenum alloyed steel- but the M21 hit the drafting boards in New Haven in aprox 1926-1927 (some say the rumor extant then was- WRA tried to purchase Parker Brothers Gun business (not the entire Parker operation, which included hardware, hand tools and first rate vises)-- but that, IMO is a rumor, albiet perhaps a valid one-
"The field is the touchstone of the man"..
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Joined: Feb 2009
Posts: 7,464 Likes: 212
Sidelock
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Sidelock
Joined: Feb 2009
Posts: 7,464 Likes: 212 |
Craig
your understanding is incorrect. Steel has a Young's modulus that is unchanged by heat treat.
Sorry Chuck, I thought that's what I was thinking. That elasticity is unchanged with hardness and both samples would permanently deform at the same point. If Young's modulus were followed, can you make the hardened sample deflect farther than the soft sample and return to true.
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Joined: Feb 2004
Posts: 13,880 Likes: 16
Sidelock
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Sidelock
Joined: Feb 2004
Posts: 13,880 Likes: 16 |
Craig
Since modulus (stiffness) is un changed with hardness the two springs will require the same force for the same deflection until the soft one reaches yells point. After that the hard spring will continue to require increased force until it reaches its yield or failure point.
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Joined: Feb 2009
Posts: 7,464 Likes: 212
Sidelock
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Sidelock
Joined: Feb 2009
Posts: 7,464 Likes: 212 |
Thanks for taking the time Chuck.
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Joined: Feb 2004
Posts: 13,880 Likes: 16
Sidelock
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Sidelock
Joined: Feb 2004
Posts: 13,880 Likes: 16 |
Craig
Sorry for the misspelling. Using a phone here. I hope I explained it well enough to be helpful.
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Joined: Jan 2002
Posts: 5,954 Likes: 12
Sidelock
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Sidelock
Joined: Jan 2002
Posts: 5,954 Likes: 12 |
Do we agree that the case shell is on the order of 0.002" thick (about the thickness of a human hair)? If so, and if the the "hard" shell had ten times the force per unit thickness trying to return the action to OE dimensions after yielding of the core, the first 0.020" of the "soft" section would balance the "hard" case shell. The "soft" has a whole lot more "meat" than does the "hard" shell.
Yep, a "soft" action will bend and spring back under firing stress. This is for the simple reason that the strain (deflection) does not exceed its yield strain. Note that stress and strain are somewhat interchangable as they are related in a very predictable way. X amount of stress will produce Y amount of strain. Y amount of strain indicates that the metal has X stress applied.
Good discussion!! Keep going until all understand.
DDA
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