Reconditioning antique locks

[Dan Fruth]

I acquired a nice 1790-1800 English made double barreled shotgun, and am reconditioning the locks. The frizzens will throw sparks, but not what should be. I am not sure of the best way to bring them back to servicable condition....Kasonite, brazing new faces, or charred bone hardening....Any suggestions would be appreciated. By the way, this double has Belgium barrels, and in good condition. I intend to shoot this piece...Thanks....Dan

[rich pierce]

Least intrusive would be a long charcoal pack deep case hardening.

[jerrywh]

 I agree with Rich. Those old lock frizzens are made of case hardened wrought iron as a general rule. Although they may appear to be OK sometimes that old wrought iron will be sort of rotten. A high heat when exposed to oxygen will burn up the metal sometimes. I had that problem before even with a tig welder. Case hardening in a charcoal pack is the safe way to go. Don't forget to temper the toe of the frizzens after quenching. Temper the whole frizzen to about 400° for an hour  and the toes to about 600° You can do the toe part with a torch . 

[David R. Pennington]

What temp and how many hours?

[Mark Elliott]

I would suggest 1625F for 90 minutes to harden.   Then temper as instructed although I usually temper to 375F.   Make sure to pack well in a crucible with pea to marble size pieces and cover it relatively well.   It shouldn't be so tight that I can't vent gas under pressure. I use heat treat foil over my crucibles and it works well.     

[jerrywh]

 I pack my stuff in charcoal about the size of a wooden match head down to powder. It is like 3/16 minus. I pack them in plain old iron pipe or even a piece of tail pipe with a lid welded one one end.
 I just sit a flat plate over the top but always have at least an inch of charcoal over the parts packed tight.  I heat to 1550 for 1 1/2hours and quench at no lower than 1450. 1500 is better. Then I temper at 350 to 400 for 1 hour or more. 400 will spark better but wear faster. Then I heat the tail of the frizzen to a blue color and let cool naturally. 1650° will sink a case faster but there is a line on temp that is not good to go over and that line is somewhere between 1650 and 1700.  If you exceed that temp. it will not destroy the part but it can leave you with a grainy looking surface. Another reason I try to stay at 1550 is because I do a lot of gold inlaid parts and fine gold inlays will alloy with the base metal at just over 1550° and they sort of dissolve.

[Dan Fruth]

Thanks for the advice....Charcoal it is then!

[JCKelly]

All heat treat advice here sounds good enough, but are you sure that soft frizzen faces are the problem? Do both locks behave about the same? Is one or the other heavily worn?
With respect, it is my opinion, and observation, that flint lock frizzens were made of solid wrought iron, with the steel face forge welded or brazed on. Brazing was, I think, used for the common commercial grade, forge welding for military or top notch sporting arms
Trying to deep-case wrought iron might give you a surprise, such as blisters raised up here & there.
The differences between wrought iron and 18th century English steels I can discuss on another thread if you wish.

Brazed frizzen steel on American lock with only modest use (I think)
Anyway some locks like flint bevel down, others bevel up. Friction, and lock geometry is important. My 10th grade geometry teacher left me with measles one summer, I am definitely not the expert here. There are a lot of smart flint lock guys on this forum, though
No good at geometry, but I am a metallurgist with some interest in history. Over the last half century I have observed that for almost all metal Widgits that don't work, "bad metal/heat treatment" is not often the problem.
There are lots of ways to screw up heat treating. Especially if you are new to the subject. Me, I'd spend a lot of time looking at the mechanics of the thing, before I put it in the fire.

[jerrywh]

 Kelly has some good points.