casehardening locks

[David R. Pennington]

Have a Chambers round faced English style lock I am using on an early southern style rifle. I have it tuned and have the exterior plate, cock and frizzen filed and polished to 500 grit. Can or should I caseharden the cock and plate? I am looking for a good durable appropriate finish but I'm wondering about the makeup of the metal and don't want them brittle hard, only surface hard. I'm not concerned about "colors" just the grey I get with Kasenit will be fine. To caseharden or not to caseharden, that is the question!

[Don Getz]

In my old age I have become lazy and do not harden anything on a lock, use them just as I get them, except to clean up
the front sides before I put some kind of finish on them.  The late Dave Dodds always case hardened the lock plate, and
it sure shows when you cock on of his guns.  In hardeniing it makes the parts glide over the surface, and, if you have the
capability to do it, I would strongly suggest it be done.    ....Don

[David R. Pennington]

Thanks for the reply. I did a Siler kit a few years ago and didn't caseharden the plate only the internals as required and it has worked great over the years. The only service it has required was dressing the washboard out of the frizzen face once. The only finish I put on it was to give it a coat or two of the homemade aquafortis stain I used on the stock. It did'nt brown it but gave it a sort of mottled antique look that I like. I think I may try casehardening this one. My main concern was if it were cast of high carbon steel it might get too hard internally and break, but my guess is it is not high carbon. The frizzen appears to be cast with different alloys at different areas if that is possible.
The most difficult task for me is getting a good fit of frizzen to pan! Think I'd rather hand inlet oct./rd. barrel or hand forge a mainspring!

[LRB]

  Your frizzen is all 1095 steel. It is most likely differentially hardened, in that the tail and screw mount area are tempered softer than the strike plate, to keep it from being brittle in use.

[Dphariss]

Thanks for the reply. I did a Siler kit a few years ago and didn't caseharden the plate only the internals as required and it has worked great over the years. The only service it has required was dressing the washboard out of the frizzen face once. The only finish I put on it was to give it a coat or two of the homemade aquafortis stain I used on the stock. It did'nt brown it but gave it a sort of mottled antique look that I like. I think I may try casehardening this one. My main concern was if it were cast of high carbon steel it might get too hard internally and break, but my guess is it is not high carbon. The frizzen appears to be cast with different alloys at different areas if that is possible.
The most difficult task for me is getting a good fit of frizzen to pan! Think I'd rather hand inlet oct./rd. barrel or hand forge a mainspring!

Casehardened locks work better than soft locks.
They are also more wear and corrosion resistant.
Chambers locks will caseharden fine.
But casehardening parts cast from 4140 require care not to through harden the part.
Charcoal case hardening requires some knowledge and skill to assure a hard surface and no damage to the part, warping, blisters/scale etc. As a friend says "do not try this at home" if in doubt send it out in other words.
Yes, the frizzen is a through hardening alloy and Chambers specifically states to NOT QUENCH IN WATER.
So casehardening as quenched in water is a no-no. The part can be coated in Kasenite to prevent decarb then quenched in light oil warmed to maybe 150 degrees or so. This should give the proper hardness and it can then be drawn back at about 375 degrees to increase toughness and in some cases improve spark.
And like LRB says
Dan

[David R. Pennington]

I probable won't touch the frizzen if it sparks ok other than to try to selectively harden the toe if it needs it. I just planned to use Kasenite on the plate, hammer, and screws.

[Bob Roller]

Back in "The Day"when investment cast lock parts were coming into use,only God really knew what those parts were made from. I used to raise "H" about the total absence of quality control in these parts but I could have gotten a better response from a Totem Pole or a cigar store Indian. I was once told nobody cared and the  volume of work in these parts was so small
that it was never an issue. I remember  getting lock plates that shattered like glass when I tried to straighten them.Then there were others that once reamed for the tumbler shaft,the hole would change dimensions to a slight egg shape and if reamed again,same thing all over again. Frizzens were a horror story because they could seldom be properly hardened to last very long or they were made from material that was harder than glass and even carbide wouldn't drill them. I think those were supposedly made from the residue of a foundry pour of turbine blades for aircraft engines. It SEEMS to be a bit better today but I still will not have anything to do with cast mainsprings,sears or tumblers or for that matter,bridles or the fly. Residue from engines or anything else have no place in a gun lock as far as I'm concerned. I once called a foundry in Ohio and got ahold of some knucklehead that would only speak in a low mumble which I think was deliberate to get me out of his hair and off his back. Too much was enough and I went on with the automobile work both in my shop and at European Motors which earned a living that muzzle loaders of any kind couldn't furnish.
Viva Mercedes,BMW,Volvo,Citroen,Jaguar XK and the occasional Duesenberg.

Bob Roller

[David R. Pennington]

Yes, I'm learning about those cast springs. I recently had one I finally gave up on. Took an old hayrake tooth to the forge and made one that works better than the cast one that came in the lock.

[David R. Pennington]

Well I did it. I casehardened the lock plate and hammer. Heated them in the forge and used Kasenit. Did the process twice to ensure even coating of the compound. Only problem was my nice straight lockplate that I had taken so much pain to true up was now warped about .035. I was extremely nervous as I straightened it back out. I full well expected it to break at any moment as I tightened the vise jaws. I clamped it in the vise with alternating pieces of heavy harness leather and squeezed it back straight. Whew! Casehardened screws and etc.., and reassembled and works great. I still have a little fine tuning to do with whetstones before I'm completely satisfied and the frizzen spring needs polished. One problem I had was that bridle screws turned in too tight and I would have had to grind off all my bearing surface to get clearance. I really should have made new screws but I tried an alternate fix which I think will work. I soldered up the threads and then recut them just a little and then turned them in tight.

[Jim Kibler]

Typically when a lock is carburized or case hardened, it is done so in a pack or in a carbon rich atmosphere.  Kasenite may help to some degree, but it results in a pretty thin case.  No need to really worry though as you haven't hurt anything and may have improved things a touch.  Case hardening is nice and I routinely do it on locks, but they can work just fine without the process.  

As to cast internal lock parts.....  I think this has been proven as a very succesful method of manufacture.  The propensity for defects may be slightly higher than parts made from wrought material, but I don't believe it's at all significant.  With a controlled process, excellent parts can be produced in an ecconomical fashion.  With regards to springs, I also don't believe there is any significant difference in the performance of cast versus wrought springs.  The applicable mechanical properties of cast versus wrought steel are so close that differences are negligible.  

Jim

[Dphariss]

Well I did it. I casehardened the lock plate and hammer. Heated them in the forge and used Kasenit. Did the process twice to ensure even coating of the compound. Only problem was my nice straight lockplate that I had taken so much pain to true up was now warped about .035. I was extremely nervous as I straightened it back out. I full well expected it to break at any moment as I tightened the vise jaws. I clamped it in the vise with alternating pieces of heavy harness leather and squeezed it back straight. Whew! Casehardened screws and etc.., and reassembled and works great. I still have a little fine tuning to do with whetstones before I'm completely satisfied and the frizzen spring needs polished. One problem I had was that bridle screws turned in too tight and I would have had to grind off all my bearing surface to get clearance. I really should have made new screws but I tried an alternate fix which I think will work. I soldered up the threads and then recut them just a little and then turned them in tight.

Quenching long parts requires their being quenched vertically and being heated uniformly.
If they are much hotter in one area than another they may warp and if dropped into the water so they land flat they will warp. If one side of a long part cools first is will warp.
I hang them on a wire when hardening with Kasenite and put them in the quench vertical.
Dan

[Dphariss]

Typically when a lock is carburized or case hardened, it is done so in a pack or in a carbon rich atmosphere.  Kasenite may help to some degree, but it results in a pretty thin case.  No need to really worry though as you haven't hurt anything and may have improved things a touch.  Case hardening is nice and I routinely do it on locks, but they can work just fine without the process. 

As to cast internal lock parts.....  I think this has been proven as a very succesful method of manufacture.  The propensity for defects may be slightly higher than parts made from wrought material, but I don't believe it's at all significant.  With a controlled process, excellent parts can be produced in an ecconomical fashion.  With regards to springs, I also don't beleive there any signicant different in the performance of cast versus wrought springs.  The aplicable mechanical properties of cast versus wrought steel are so close that differences are negligible. 

Jim

Casehardening need not exceed .005-.006".
Very useful and durable cases can be achieved with Kasenite. I have a mild steel tumbler that I kasenited with a torch it has been shot extensively and is still working as it always did.

Deep case on a thin section part can result in a through hardened brittle part. Sear noses and tumber notches come to mind.

Of the castings I got with a Rifle Shoppe lock both the tumbler and mainspring were junk. The lock plate required welding and still has a pit in the pan I should fix. The quality of the cast part is very much dependent on the people doing the casting.
As friend in the firearms industry once said "you mean you bought a casting and did not buy a welder to go with it?"
Its not the process, its the variation in the care and workmanship. I am confidant that any casting I buy from some suppliers will be good. But this is not universal.
I would PREFER to have all parts CNC machined from bar stock, all springs from forgings,  but that's just a dream.

Dan

[Bob Roller]

IF the tooling (moulds) are first class and that means milled and polished cavities,probably higher quality parts could be produced. Lynton McKenzie told me that he saw such a level of quality control from moulds made in Switzerland and saw some fine flintlock pistols with locks made from these parts. ALL of these pistols went to a German distributor and Lynton was told that no American dealers or distributors had inquired about them even after being notified that they would be available. I was told by several foundries that the level of quality control I wanted would bankrupt a government. I suppose they were right but it spoke poorly as to what was then the state of the casting art when I made that inquiry which was about 1980 or thereabout,
I prefer to make all internal parts in my own shop and I am not interested in mass production.
I can feel the difference between a cast mainspring and a forged one. Same thing goes for the function of the tumbler,fly and sear.
The little Ketland lock I sometimes make has all the parts,both internal and external made with waxes that are injected into milled aluminum,polished cavity dies that cost $5000 in 1955 to get made. I use only the external parts because in 1970,I went to the linked mainspring and a bridle with two upper screws for more rigidity. I never did use the internal parts produced in those dies but they are probably available if someone wants them.
I have made another Ketland that never did have any cast internal parts because only the external parts are available.It has a heavy frizzen that can be fitted with a roller and
reenforced cock. This is a small lock and is expensive because of the labor intensive nature of small mechanisms like this lock  requires. As far as I know,no one else ever tried to make locks on these parts because of this.
Maybe someone will. I have one set of these parts and they are committed to a gunmaker in Pennsylvania.

Bob Roller

[LynnC]

Dave,

I would chuck up the screws and file the underside of the offending screw heads.  If you cased them you'd have anneal first.  Even easier done if you can use a lathe.

Just a thought and hope its of use.........Lynn

[Jim Kibler]

I believe what matters is how the parts are fitted up and finished and not so much whether they are from castings or wrought material.  I accept that castings require machining and / or hand finishing.  Properly fit and finished I don't believe a person could detect the difference between the two, even on springs.   I think that sometimes ideas or beliefs get started and take on a life of their own, with sometimes little tangible proof to justify them.   Just my opinion.  I've never been shy about expressing it either!  

[Jim Kibler]

Casehardening need not exceed .005-.006".
Very useful and durable cases can be achieved with Kasenite. I have a mild steel tumbler that I kasenited with a torch it has been shot extensively and is still working as it always did.

Deep case on a thin section part can result in a through hardened brittle part. Sear noses and tumber notches come to mind.

Dan

As to case hardening of the plate, cock, top jaw and top jaw screw I don't see the use of Kasenite as a good process for the job.  Any modern lock will work well with no case, so a case of .005-.006" will work fine as well, I would suspect  I feel confident in saying original 17th and 18th century carburizing proceses on wrought iron typically produced deeper cases.  A deeper case adds considerable strength to the part, not just wear resistance.   Seems we've had this discussion before  Pack hardening is not too complicated and works well for hardening the parts mentioned above.

As to internal parts, I would prefer to use either tool steel or pack harden to a deeper case.  I would not feel comfortable with kasenite for a tumbler or sear.  It may hold up and work fine for a long time, but since I sell everything I make, I want to be as sure as I can be that something will hold up.  Again just my opinion.  As to thin parts being carburized too deep, it's a simple process to draw these areas back a little more than other areas.  What I mentioned concerning deeper cases on 17th and 18th century work and wrought iron, applies to internals as well.  I think drawing back thin areas was well understood.

I suspect the affinity for shallow cases are a result of steel being used for the base material and the desire for colors.  Low temperatures produce better colors but shallow cases.

Jim
 

[JPK]

I color cased hardened this lock and it did make a noticeable improvement in it's speed. The frizzen was left alone and the warpage was about .005" on the lock plate. I've found that reducing the temperature just before quench produces less warpage yet gives a good hardness. Also you can get good colors if you mix a bit of Kasenite with lump char coal for your pack then procede as normale.

[Jim Kibler]

All other things kept constant, In my opinion I don't believe any change in mechanical lock speed would be humanly perceptable.  Don't get me wrong, I have probably case hardened 90% of locks I've used, some being fully custom locks, but I'm not convinced the change in lock time is significant and don't believe it would be perceptable.  I would like to hear Larry Pletcher's take on this.  One thing I recall from a demonstration he presented is how significant of a change in lock time was necessary before it could be detected with the ear.  This would be a simple and interesting experiment for Larry.  Test a fully polished, tuned lock before case hardening and after.  I'll go on the record now and predict the difference in lock time will be small, likely not statistically different when accounting for the variations between tests.

[Bob Roller]

I like case hardening on a caplock plate and hammer and it looks good on a bridle but I want no part of it on the sear or tumbler. I agree with Dan about using oil hardening tool steel for the sear,fly and tumbler. I use Starret or Sheffield 0-1 for the sear and fly and Stressproof 1144 for tumblers. Those two work for me and I speak from the point of view of actually making locks as opposed to assembling castings.
Lock time is much improved by precise fitting of the tumbler and bridle alignment PLUS the preloading of a properly made mainspring that has a whip like action when released from the confinement of the full cock position.
I was a bit surprised by the rapid action of the Twigg lock which I thought would be a bit sluggish even with the precision fit parts and preloaded mainspring. I was wrong on that one.That lock,in spite of the size is fast and I am pleased with it. So far,feed back has been positive.
Getting back on point to case hardening,I do it on rare occasions on caplock plates and hammers. I use Kasenit and heavily nitrated water for a fast quench and it seems to work real well on double set triggers made from low carbon flat ground stock. I am speaking of the triggers, NOT the trigger bar. I also notice that recent purchases of LCFG seem to indicate a bit harder material than some bought previously.
Does anyone use this material other than me and if so,have you noticed any difference?
The 0-1 is what it is and I have noticed no difference in it for decades.
The 1144 is a peculiar material that machines almost as easy as 12L14 but can be oil hardened and I also have used it since the early 1960's with few problems reported. One fellow decided to case harden a tumbler made from it and quenched it in very cold water and ended up with a 9 piece tumbler after a couple of shots.
Mainsprings and sear springs are made from 1075 that I buy in annealed condition and sheared to a specific width. Frizzen springs are castings and since the advent of 6150,little if any trouble is reported by myself or any other lock makers.

Bob Roller

[Dphariss]

All other things kept constant, In my opinion I don't believe any change in mechanical lock speed would be humanly perceptable.  Don't get me wrong, I have probably case hardened 90% of locks I've used, some being fully custom locks, but I'm not convinced the change in lock time is significant and don't believe it would be perceptable.  I would like to hear Larry Pletcher's take on this.  One thing I recall from a demonstration he presented is how significant of a change in lock time was necessary before it could be detected with the ear.  This would be a simple and interesting experiment for Larry.  Test a fully polished, tuned lock before case hardening and after.  I'll go on the record now and predict the difference in lock time will be small, likely not statistically different when accounting for the variations between tests.

Yeah Larry would have to test this. But it would require testing the lock, having it casehardened, then tested again.

Dan

[Jim Kibler]

I like case hardening on a caplock plate and hammer and it looks good on a bridle but I want no part of it on the sear or tumbler. I agree with Dan about using oil hardening tool steel for the sear,fly and tumbler. I use Starret or Sheffield 0-1 for the sear and fly and Stressproof 1144 for tumblers. Those two work for me and I speak from the point of view of actually making locks as opposed to assembling castings.

Bob Roller

Hi Bob,

The vast majority of locks made in the 17th and 18th century would have had case hardened tumblers and sears.  Actually case hardened (pack hardened) wrought iron.  Though tool steel might be a better material, I think the effectiveness of case hardening on tumblers and sears has been thorougly proven.  As I understand it, the use of steel for internal parts began to predominate in the 19th century.  With that said, I have used O1 for the internals of custom locks I've made.  Here are a couple examples of locks I've built.  The first is a 1750's British lock made entirely by me.  No castings used. The second is a lock in progress that is of a French style from around 1690.  Again, every part made my me and no castings used.  All aspects of the locks shown including the internals are appropriate to the time period of the lock.

[Daryl]

Jim- that French lock is soooo sexy.

[Jim Kibler]

Jim- that French lock is soooo sexy.

I'm with you Daryl.  That's not a compliment for me, but for the French of this time period!  In my view their work is so underappreciated.  Especially 17th century baroque stuff.  I will admit that at times, I think their work was overdone from a decroative standpoint.  Not always but sometimes.  I think it's important to look beyond this and appreciate the forms, designs and decorative elements used.  Amazing stuff.

Recently I read a description that Lenk's book "The Flintlock", which deals primarily with 17th century French work, was "basically useless".  I might be taking this somewhat out of context, but I can't disagree more.  French firearms were inovative from a technological and decorative standpoint, influenced much of Europe and England and had a largely indirect but significant impact on firearms made in this country. 

I might add that this lock will have relief borders, some relief chiseling and engraving as well.  

Jim

[Acer Saccharum]

I think that sometimes ideas or beliefs get started and take on a life of their own, with sometimes little tangible proof to justify them.

Out of the mouths of babes come words of wisdom.

Pipe crucible packed with charcoal, held at red heat for about an hour in a charcoal fire.


Quench in a bucket of lukewarm water. If thee useth a plastic bucket, put a metal spacer screen at the bottom to catch the parts.
Pipe crucible, welded on bottom, with lathe turned lid and machined crucible opening.


An example of case coloring with the above non-scientific method. Plate, cock, top jaw, frizzen, screws and internals were treated all at once. Only things not cased were the main and friz springs.

[davec2]

Tom,

Do you block the plate?  And if so, do you have any pictures of your blocking?

Thanks

Dave C