A lock project

[John Vaccaro]

Well, Zonie, at least you understand why I asked the question. Case hardening is so thin, and so hard that it wears the flints, and doesn't last very long once it is penetrated. IF you case harden a frizzen on a gun that is going to be shot very much, you have to plan on re-case hardening it about every year, and sometimes more often. I think with replacement frizzens now available for most everything, it would pay to get one made from a proper cast steel, and harden it like he did the springs, and then draw it back by tempering methods, too.

When cast steel is hardened it looses carbon on the surface. Case hardening using "kasinite" replaces the lost carbon and makes the lock spark much better. John

 

[paulvallandigham]

John: I don't think so. The carbon in steel is bonded to the iron molecules, and what you see as char on the surface comes from the quenching medium, or from the crud in your oven or furnace. What little might be lost in the hardening and tempering process does not affect the steel's ability to throw good sparks. Modern flintlock frizzens are hardened and tempered all the time, and give very good service. If you read Oscar Gaddy's articles about bone charcoal case hardening in the 1996-'97 issues of Double Gun Journal, you will learn that the case hardening is most likely silica that is melted into the surface of the steel. It makes the iron glass hard, and thereby protects it from ordinary corrosion. Unfortunately, it is less than 1 thousandth of an inch deep, and does not survive being cut by flints for very long. And, since flint is made of silica, you are striking rock with rock, and that is a good way to ruin a flint or dull it prematurely. Tempered steel has a give to it, and that is what the flint wants- " Give Me some steel at high temperature to light this powder charge in the pan ".

 

[Roy]

Why would you case harden the frizzen, rather than harden and temper it all the way through? A flint will cut through that case hardened surface fairly quickly, and then the thing won't spark worth a darn.

Just very curious!

Sorry boys for not replying quicker, I was out snipe hunting.
To pull a quote from TRS: "We use 4140 steel on all our lock parts except frizzens and springs wich are 6150. These are oil hardening steels, but we don't reccomend oil hardening, but you will find that if you case-harden the lock plate, internals, and frizzenthen use a water quench it will give you a finer finish and smoother bearing surface. You are not adding anymore carbon by doing this, but you are kepping the parts from loosing any carbon while you are bringing the part up to the correct heat range (1650-1675 or very bright redish orange). Thanks for the good question :thumbsup: .

 

[Roy]

What's your process for aging the metal?

Any way I can get it. :grin: For the frizzen and cock, I boiled it a bit in a bleach water mix for a few minutes. Darkened some parts on the plate using "Plum Brown", and let some parts go a bit with out any oil after heating and I also like a wire brush to nock off the heavy rust.

 

[Roy]

Thru hardening steels should not be case hardened.

Like I told my chemistry teacher once "I think you are mistaken". :grin: :grin: :grin:
:shocked2: Sorry Zonie, just kidding... :haha:

 

[Zonie]

That's ok Roy.

I'll stick by my guns, so to speak. I think the amoung of carbon lost during heat treating newlly made frizzens is so trifling that it has no effect on the final product. I have never had a problem with the frizzens on the "kits" I've built.

By the way, "These are oil hardening steels..."

I don't agree with water quenching oil hardening steels either. Seen too many of them break from doing this kind of thing.

Different strokes, I guess. :grin:

 

[Roy]

I have only found that when quenching Really thick pieces of steel that cracking occurs. The cracks are formed when the metal on the outside is cooling(shrinking) quicker than the inside, so by oil quenching we are slowing the cooling process. When even building the wall gun parts I used water to quench with no ill results.

 

[Roy]

I guess I passed the test the customer was very happy with the end results. The lock slipped back into the stock without any problems after he removed the drum and replaced it with a liner. :winking: :grin: