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

I thought putting a loose action 'back on face' did not involve any adjustment to the frame. Was the smith saying that each shot was bending the frame, but all was good with the pin, face of the barrels, etc. I wonder if it was just a pain in the tail gun, that was getting into more time than the job was worth.

The smith was welding the hook and then fitting it. Then after a few shots it would go loose again. Finally figured out the frame was bending (not flexing).

My post was unclear. Thanks Craig!

Best,

Mike

Don,
The casehardening I had these experiences with were not guns, but they were casehardened articles in the nuclear/aerospace biz. I was a toolroom machinist modifying these parts. I don't know exactly what process by which they received their casehardening. It could have been any of the "casehardening" processes to a low carbon steel.

I've milled and turned such parts over the years. The basic approach was always to take a deep enough initial cut to get under the hardened layer. What resulted in all circumstances was the typical dull milled/turned finish of the softer metal and a transition to a shiney-er (technical term) surface finish in the harder areas. It's common for machinists to get a "feel" for how hard metals are when they machine them. This comes from not only how hard they percieve the cutter and machine are working, but also what the finish of the metal looks like. Harder steels leave a much finer finsh. The harder the steel is, the finer the machined finish. Conversely, soft steel leaves a dull and sometimes rough finish (depending on grain size). Maybe Miller can cite some of his experiences as well.

Sounds like too hot of a load to me.

Let me be explicit, case hardening and heat treating are two fundamentally different processes.
One relies on a temperature/time profile to increase the bulk tensile strength of a material and the other reiles on the diffusion of carbon into the surface of a material to increase the surface hardness. The only commonality is heat.
http://en.wikipedia.org/wiki/Case_hardening
-Dick

Where's Ed's torch fit in ?

Dick,

Sorry that my post was confusing. Heat treatment is a general term that can describe color case hardening or through hardening. Both use heat to treat metal.

The better terms to use when describing the two types of metal treatment you are referring to are color case hardening and through hardening.

As my previous post suggests, working to level set first and take all these different observations is a must when discussing something this technical in nature.

Jason

http://www.precisionheattreat.com/difference.html

The most common question about heat treating

What is the difference between case hardening and through hardening?

The most common metal is steel which is available in many different alloys. The most common type of steels are:

1: Those which may be grouped under the heading "mild steel" and generally contain less than 0.25% carbon.

2: Those classed as medium to high carbon which contain carbon over 0.25%.
medium carb. 0.25% - 0.5%
high carb. 0.5% - l.0%

The through hardening process is used on medium and high carbon steels. Case hardening is used on mild steels.

Hardening occurs during heat treating when the steel (containing sufficient carbon) is cooled rapidly (quenched) from above its critical temperature. This temperature varies for different alloys but generally is in the range 1500oF- 1900oF.


A mild steel treated in this manner would show no appreciable increase in hardness. In order to make this steel react its carbon content must be increased. In the case hardening process the surface layer of the mild steel has its carbon content increased by a prolonged contact at a high temperature with a chemically reactive source of carbon. If this steel is subsequently quenched it will harden the surface layer, also known as the case, -hence "case hardening". The case depth will generally be from two thousandths of an inch up to one hundred and fifty thousandths of an inch. However the most common depth is in the range .020" - .030".


lt is important to choose the correct steel and the appropriate process to achieve the desired end result. For moderate strength with moderate surface hardness choose a medium carbon steel - through hardened.
For a very hard surface where a lower core strength is acceptable choose a low carbon steel - case hardened.


MILD STEEL CANNOT BE THROUGH HARDENED

MED. & HIGH CARBON STEEL CANNOT BE CASE HARDENED
(although other surface treatments are available)

The process which adds the carbon to the surface of low carbon steel is "Carburizing". This carburizing process itself does not add hardness other than the small amount of higher carbon steel over low carbon steel. The subsequet quench from an elevated temperature produces the hardness just as it does in a higher alloy through hardening steel. The carburized low carbon steel will harden only to the extent its carbon has been raised high enough to be effected by the ""Heat Treatment". Steels with a higher carbon allooy do not need (in fact is is normally not desirable) the carburizing step, but the heating & quenching part is essentially the same heat treatment as given to the other. Exact alloy content determines the quench medium & thus we have water hardening, oil hardening & air hardening steels.
The hard outer surface over a soft core has led to the term "Case Hardened" being a generally accepted term, but technically it is carburized & hardened, the hardening being done by heat treating. As previously stated it is most often combined into a single operation. Never-the-less the heating & quenching is nothing but plain old heat treating.
When carburizing & hardening parts in the machine shops I worked in we always drew the hardening to a temp of around 300�-350�F after being quenched. This left the surface at virtually maximum hardness but was done to prevent surface checking of the surface. I saw one piece on which this step was omitted & the following day its surface was full of small cracks. I do not recall ever seeing this mentioned in relation to CCH of gun frames & have often wondered why.
Even on a through hardening alloy steel if it has much thickness there will be some gradient to the hardness, as the center simply cannot cool as fast as the surface, resulting in some loss of hardness to the core, though certainly not to the same extent as a case hardened part.
As a general rule parts carburized by the molten
Cyanide process do not acheive as deep penertration of the carbon as those carburiced by the charcoal "Pack" process. I have never worked where the Cyanide process was in use, but used numerous which had been so treated.

now the plot thickens. let us say the poster's fox receiver is made of the post 1912 chrome-vanadium-nickel alloy steel that fox called chromox. how does he or anyone else who annealed it, get it reheattreated by quenching? forget about the case hardening. temp and time parameters? what is the rockwell target? have any of you men who had fox receivers redone by noted restorers, ever been told how hard your receiver is on the standing breeches, water table etc?

Fox used Chromox steel (marketing name) on the barrels NOT the receiver forgings.......