doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Shooting Fox with annealed frame?

My understanding is that at least a couple of the well known CCH outfits will accept 4140 to CCH. It doesn't apply to classic receivers, but they manage the process on an alloy that can deep harden.

I noticed the 1.9mm depth of case for 8620 was at much higher temp. and much longer duration than typical reports for gun part CCH. So chances are the significant sounding depth does not actually happen if 8620 is used in one of those repro. single shot receivers.

Both Turnbull and Bachelder will color harden a Parker Repro. I'm not sure what a Parker Repro is made from. I do have an open question over in the Parker Repro forum. But I suspect it's a 4140 frame.

I recall asking Oscar Gaddy about color hardening a 4140 gun and he suggested that Turnbull has successfully implemented a process for that.

Suppose we have a beam supported at each end and a heavy load midway. As that load was placed on the beam and the beam deflected the bottom of the beam would be placed into tension and the top of the beam into compression. If one were to graph the tension and compression in a cross section of that beam from top to bottom there would be a point where it is in neither tension nor compression. That point is only in shear. So that zero tension point contributes very little to the yield strength of the beam. And as you go to the top or bottom of the beam the compression and tension go up until they reach the top or the bottom. If the beam were an I beam the flanges on the I beam add strength exactly where the most tension and the most compression occur in the beam. The beam will take more load (pounds) before it yields (permanently bends) compared to another beam that was the same height and cross sectional area but with a rectangular cross section. And I vaguely remember that the distance from the flange to that point in the beam which is neither in tension nor compression is a major component of designing a beam.

And in a receiver the case hardened outer metal increases the the total yield point of the receiver. Pounds per square inch tension is not the only factor, it is how far that tension is from the zero stress point of the beam.

And the closer to that zero tension point in the beam the less the strain (stretching or compression) and the further that point is from it's yield point. And the less that point contributes to the resistance of the load because of the spring rate.

So it is not a simple case of calculating the percentage of the cross sectional area that is case hardened and pro-rating it's increased yield strength into the total strength of the action.


Thanks,


Mike

"And in a receiver the case hardened outer metal increases the the total yield point of the receiver. Pounds per square inch tension is not the only factor, it is how far that tension is from the zero stress point of the beam."

Case hardening has nothing to due with 'yield point' if your are referring to the point where steel in tension trasisitions from elastic to plastic deformation. Case hardening affects the hardness of the surface and the values are not additive.

"So it is not a simple case of calculating the percentage of the cross sectional area that is case hardened and pro-rating it's increased yield strength into the total strength of the action."

I have never heard of a calculation like that?
Both Hardness and Yield Strength are measures quantities and are not calculated nor is there any quantity defined as "total strength".
-Dick

It could be argued that gun barrels resist the most forces on firing. I also suspect that classic low carbon receivers were intended to fail slowly, generally bend instead of reaching a sudden fracture point.

If we are just talking about the effects of casehardening or through hardening on a given double gun frame, no matter how high the hardness of the frame is raised, it won't change the amount of deflection of the frame when fired at all.

The stiffness of a gun frame will not change from hardness nor changing the steel from mild steel to chromoly, hard or soft.

The stiffness of steel is pretty much the same thru all the alloys and unchanged by hardness.

Low carbon recivers were used because that was the extent of the Metalurgy at that time in history.

"Sudden fracture point is commonly known as Brittle Fracture and is a condition that a steel can be put into if not heat treated properly known as Martensite.
Recievers were annealed to remove the Martensite structure.
Iron along with its alloying elements form the many phases that steel can go through due to its manufacturing. These are referred to as Phase Diagrams.-

http://web.utk.edu/~prack/MSE%20300/FeC.pdf

The following is a good treatise. Note the section about Martensite.
-Dick

http://web.utk.edu/~prack/MSE%20300/FeC.pdf

"The stiffness of steel is pretty much the same thru all the alloys and unchanged by hardness"

What is stiffness?

Never miind. Stiffness is a quantity used for a structure and not a material. Elasticity is the term used for a material. I suppose one could measure the stiffness of a reciever but I have not heard of it being done.-Dick

"Case hardening has nothing to due with 'yield point' if your are referring to the point where steel in tension trasisitions from elastic to plastic deformation."

Case hardening increases the yield point of the case hardened metal.

My Marks "Standard Handbook for Mechanical Engineers" is at the office but it states that case hardening increases the yield point, which is the point (stress) at which steel plastically deforms and gives examples of different results for different case hardening specifications.

"I have never heard of a calculation like that?"

Dick if you will look at the sentence I quoted from Rocketman I was trying to counter his point about the relatively small cross sectional area of the case hardened metal compared to the total cross-sectional area in regard to the plastic bending of the action. I think Rocket was arguing that the small percentage of the case hardened steel is not enough to change the plastic bending point of the receiver. I wasn't arguing for the math model but against it.


Thanks for the comments. I have learned much on this thread.

Mike

Edit: "My Marks "Standard Handbook for Mechanical Engineers" is at the office but it states that case hardening increases the yield point, which is the point (stress) at which steel plastically deforms and gives examples of different results for different case hardening specifications." is incorrect. It does not say what I wrote in this post.

"What is stiffness?" Spring rates are a measure of stiffness, pounds/inch, foot-pounds/degree etc...