Lock hardening

[chawbeef]

Does a new lock, say a L&R lock from TOW require hardening??..............Daniel

 

[Zonie]

It shouldn't need any hardening.

Although the tumbler, sear and fly (if it exists) are all soft when they are cast and machined, they all should be hardened and tempered by whoever made the lock before it is sold.

If someone buys one of the Siler lock kits, the parts are soft and require hardening and tempering by whoever builds a lock from it.

 

[chawbeef]

Thanks for the reply Jim...............Daniel

 

[Eterry]

Hi Jim, while you're on the subject does the frizzen need to be hardened on the siler kit as well? I didn't know the fly, tumbler and sear needed hardening as well...good info.
Thanks
ET

 

[dave_person]

Hi,
On all Siler kits I've built (quite a few) all of the internal parts (tumbler, sear, bridle, and fly) need to be hardened and tempered properly. The frizzen also needs to be hardened and tempered. The only parts that are heat treated are the springs. In addition, I always harden and temper the lockplate, pan, and flintcock. That prevents the flintcock from peening the shoulder on the lockplate and hardened steel resists rust. The only time I would not do that is if I plan on browning the external parts. However, I rarely brown locks anymore, rather I leave them polished bright or tint them during my case hardening process.

dave

 

[Gustavo Hoefs]

I am assuming (?) these cast steel parts are non tool steel ? i am am curious about the process for making the large spring on the inside of all the commercial locks, are these cast or are they forged? I have worked with precision ground steel plate and drill rod I usually use O-1 ( oil hardening #1) and have great results on small parts. My process is rather basic cut with jewelers saw shape, form, bend etc. for hardening / tempering I heat to critical temp then quench in vegtable oil and temper in electric fry pan @350 degrees 30 mins for non spring or contact parts then quench and approx an hour to hour and half for a spring then quench. I dont understand how a cast spring can be possible but then the manufacturers do it all the time so I know it is possible

 

[dave_person]

Hi,
Cast springs are often 5160 steel. They make fine springs when hardened and tempered properly but I prefer forged springs from 1075 steel. O1 steel is fine for tumblers and screws but hardening and tempering all parts must be done carefully. For example, the tumbler and sear need to have the same hardness so that one does not wear on the other.

dave

 

[Zonie]

I am assuming (?) these cast steel parts are non tool steel ? i am am curious about the process for making the large spring on the inside of all the commercial locks, are these cast or are they forged?

The cast parts that need hardening like the tumbler, sear, fly and frizzen are all made from alloy steel that can be hardened.

They all are oil hardening steel so quenching them in water can be dangerous, sometimes resulting in cracks.
Just quench in oil and everything will be find.


The cast steel used for springs has a very fine grain structure. That allows them to bend without cracking.

Does this make them as good as a forged spring?
IMO, it does not but they seldom crack and they are inexpensive to make so I guess in the interest of keeping costs down, they'll do.

 

[ddoyle]

The plate and the cock should be case hardened. It does not seem to be a common procedure these days but it was DEMANDED by just about every State, Institutional and Private customer of Flintlocks for a couple hundred years. ( reference Tower of London specs for Bess-baker etc)

Makes perfect sense. Reduced friction, reduced wear, reduced corrosion and just generally good practice.

How to harden a plate? Stay tuned: got a currently flat plate, some cherry red and torch standing by. Hope is that the plate is still flat and un-warped when I am done.

 

[dave_person]

Hi ddoyle,
Using the lockbolt screw holes, attach 1/8-1/4" thick metal plate to the inside of your lockplate. Then heat and quench. The metal plate (called blocking) will prevent warping.

dave

 

[Artificer]

Hi ddoyle,
Using the lockbolt screw holes, attach 1/8-1/4" thick metal plate to the inside of your lockplate. Then heat and quench. The metal plate (called blocking) will prevent warping.

dave

Dave,

Dumb questions, but I just have to ask. It sounds like you are hardening a steel lockplate? Or if you are using Kasenite or some other case hardening compound, how do you get the compound on the interior side of the lockplate? Do you just lay a layer of it on before screwing the lockplate to the metal block?

Gus

 

[dave_person]

Hi Gus,
I pack harden with wood and bone charcoal. I assume ddoyle is hardening a steel plate that can be through hardened just with heat so the blocking plate doesn't interfere with a case. If case hardening, I put spacers on the bolts to separate the metal plates. In that case I also anchor one end of the block with a screw going into the sear screw hole. Keep in mind I don't worry about blocking if the lockplate is thick like a Chamber's round-faced English lock. Warping also can be prevented without blocking if the plate enters the quench vertically from one end. However,during my pack hardening process, the plate is packed in a retangular metal box with a lid on one side so it drops into the quench like a brick on its face not edge. That is when blocking is really needed on thinner plates. FYI, my case (pack) hardening process involves heating the plate in its pack to 1575-1600 degrees F for 90 minutes and then quenched in about 10 gallons of room temperature water. Then the plate is tempered at 490-500 degrees for 1 hour. If I am trying to produce colors in the case, I reduce the hardening temperature to 1450 degrees but may heat soak the part for 2 hours before quench.

dave

 

[Vaino]

Hi Dave....have used my squirrel LR for nearly forty yrs and the soft small Siler flint lockplate isn't indented from the cock hitting it and the cock stop ledge isn't mushroomed at all. Possibly hardening the lockplate might do some good if the rifle is shot an extraordinary amount, but most aren't.

If the present day manufacturers of flintlocks were to harden the lockplates, a sizeable price increase would be the result...caused by increased time, labor and reject rate. Because most flintlocks aren't shot that much, they probably figure it's not worth it.

Have used the soft lockplated Siler flint w/o any problems for many yrs and really didn't feel the need that it be hardened.

You make high quality MLers and hardening the lockplates just reinforces that, so definitely can't criticize you for doing so.....Fred

 

[Artificer]

I really appreciate you going into that kind of detail to explain blocking while case hardening. I can see how adding another screw through the sear screw hole would be necessary, when using the washers, to prevent warping between the two sideplate screw holes. Thanks so much for the info.

Gus

 

[dave_person]

Hi Fred,
I also never had trouble with Siler lock plates getting peened if not hardened, but I did with Chamber's round-faced English locks and some Davis locks. I don't brown my locks anymore so the hardened plate and flintcock help resist rust. I really like how the hardening resists rust in the pans. Some locks are simply polished, with others I add 1/4 cup of potassium nitrate to the quench water, which tints the metal a light blue-gray. Then after tempering at 490, the plate has a attractive blueish-amber tint. When I post pictures of a New England fowler I am about to finish you will see what I mean.

Gus, you are welcome as always.

dave

 

[jerrywh]

Countless of times I have heard members cririsize guns for not being period correct Well if the lock isn't case hardened it isn't period correct. The originals were all case hardened and it was done by the method described by Dave Person. I have done it in a wood stove and also in a wood bonfire. That is the reason very few locks were engraved on American Long rifles. The imported locks came here case hardened.

 

[ddoyle]

Wow this thread turned in to a note taker!

Huge thanks guys for shedding so much experience and knowledge on the subject.

Really glad I checked in here before quenching the plate with out backing.

Thanks again, off to make some heat and fun.