case hardend locks

[NAF#123]

Any one know any history or when case hardend locks were first made ?

[Jim Kibler]

Probably as long as locks have been made.  With soft wrought iron being the material most of the parts were made from, case hardening was required to increase wear resistance and durability.

[smart dog]

Hi NAF,
Here is an excerpt from Espingarda Perfeyta, a Portuguese gunsmith manual written in the lae 1600s:
 "In order to temper iron, however soft it may be, so that it may become as hard as steel itself, the most common and easy secret that there is, is to roast some ox-hooves on the fire, without their taking light, and when they are cold to hammer them, and add to them as much salt, and one part chimney soot.  All must be well crushed and put together in any vessel, and then on this is poured enough urine in order to incorporate it all.  And let this advice be taken, that the older the mixture be the greater is its force and activity.  And then on a steel plate are placed the pieces which are to be tempered so that they fit well, either one or many, and under it a layer and over it another layer of the aforesaid  mixture, is such a manner that the pieces be well covered.  Then they are put on the fire covered with coal, using the bellows until the fire be strong, and then a fan shall be used for about a quarter of an hour, heating this material until it be burnt, and when touched with an iron, falls away.  When it is thus burnt, the pieces shall be put into water, and they will be as hard as steel.  Let warning be taken that this semblance, and hardness which the iron attains, does not enter it, but is given to its exterior, entering only to a certain limit, which does not happen with steel, which totally, both outside and inside, remains hard." 

As you can see, case hardening goes way back and as Jim said, probably predates the earliest lock mechanism.  "Color" casehardening became popular in the gun trade during the early 19th century, although some colors probably resulted in many ancient casehardening efforts.

dave

[NAF#123]

I'm sorry it was late when I posted that, it was the "color" case hardening that I was wondering about. I guess my real question is if the color case hardend lock were used during 1804-1843 ?

[smart dog]

Hi NAF,
As I said, any lock that was casehardened (and left unblued) had the possibility of some color.  Therefore, many early locks may have had colors but are now simply gray because the colors were polished off over time.  I think methods to produce bright colors as a finsh by adding potassium nitrate or aerating the quench probably evolved during the early 19th century.  It became more common toward the middle of that century.  I am sure you can find locks produced between 1804-1843 that were color casehardened in some fashion.  For example, lockplates on some models of muskets manufactured at Harpers Ferry after 1812 were color casehardened.  I am sure you can find much earlier examples as well.  Often the part was laquered or varnished after heat treating to preserve the color as much as possible.

dave

[NAF#123]

Howdy Dave,
I thank you kindly for informing me about that, it was something that has been on my mind for a while now.

[B Shipman]

As has been said, all locks have to be hardened and tempered acording to the use of the part, but as exterior finish goes, just casing leaves a surface that is very difficult to finish. A rock hard crust. Color casing, without oxygen, is soft, the steel is hard but the finish is soft and easy to take off, and whether it is left  or finished bright was a matter of style and period. British work, in the early 1800's, began to put value in the nice colors produced, and left them, and of course, the time and cost to take them off.

[Dphariss]

As has been said, all locks have to be hardened and tempered acording to the use of the part, but as exterior finish goes, just casing leaves a surface that is very difficult to finish. A rock hard crust. Color casing, without oxygen, is soft, the steel is hard but the finish is soft and easy to take off, and whether it is left  or finished bright was a matter of style and period. British work, in the early 1800's, began to put value in the nice colors produced, and left them, and of course, the time and cost to take them off.

I used to restock CC hardened Shilohs from time to time and the color will tolerate a fairly soft scrapers while shaping. I used to scrape to the metal to get the wood down to metal level with no damage to the color.
This said the sun will fade it, even rubbing with a finger can wear away the color.
Its not very durable really and most CC colors are faded to silver or gray in time. Rust or Charcoal blue is much tougher.

Dan

[doug]

      In the Portugese description, I wonder what the purpose of the salt was relative to carburizing the iron?  It was added directly and would presumably be present in urine which was also added

cheers Doug