casehardening locks

[Acer Saccharum]

I did block the plate, Dave.  Sorry, no pitchaz.

This means I had a backer plate bolted to the lock plate to try to prevent warping. It is just a bar of 1/4 x 1" steel, with 1/4 tall spacers between lockplate and backer bar, screwed together in at least three places.

The best way to prevent warping of the lockplate is to have it enter the bath vertically.

I have heard that some builders don't bother to block the plate, just make sure it hits water nose or tail first.

[kutter]

Nice looking case colors.
Your 'non-scientific method' is not all that far off from what we used when I work for one of the big names.

We used a welded up 'box' with a flat cover that just sat on top,,no threads or seal. 1/4" steel.
The covers did have an over hanging lip all around. But aside from sitting flat, certainly not a tight seal.  
Oven time was 1.5 hrs to 2hrs depending on the parts being done. Never more.
1430F tightly monitored
Bone and wood char mix. Just a couple of different ratios for all the different patterns.

Quench water was pre heated to 90F.
No additive to the water,,no air bubbles circulating. Use water once and dump it. (DEC wasn't happy with that though)

Parts were never 'blocked' to prevent warpage.
Sometimes I wish they had been! But 99% of the time, warpage was not a problem if the temp, time and quench technique was followed.
Sometimes a thin part was backed with a steel blank so it retained heat better. Those thin areas would cool quickly in the drop and come out grey or pale blue if not done so. Some factory guns patterns naturally had that in their pattern so any backing/blocking for heat retension was left out on those.
Same bone char (no wood char) is used in the charcoal blue/carbonia blue process.

[Dphariss]

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
 

I only use Kasenite for small parts and its never let me down if I use it right.
Case depth. Case hardening need not be .008 to .010 deep be effective and long lasting
Trying to drive the case deeper than .006 +- has its own risks IIRC.

Just curious. Have you ever had case depth measured? On old or new work?
I do know that it varies a great deal on old work, even 19th century parts. It is also possible to do the colors with no hardening at all as you point out.

I know an expert in charcoal hardening, an actual "master" if you will, who HAS had his work checked and he has done a lot of it and still does a several heats a week. I tend to take his word on all things heat treating.

I see no point in casehardening parts I have a lot of work in when I can have them done by someone who actually has a track record. Besides it give me an excuse to talk to friends.
So I "don't try it at home". My interest does not overcome the stuff I would have to buy and make to do it right. Besides I know an expert.
Dan

[Bob Roller]

I recall what lock maker Chet Shoults of Lapeer,Michigan once said about case hardened frizzens and that was "it's so thin there is only one side to it". Something to keep in mind is this:
We shoot for sport,hoots and giggles today whereas in the day when the long rifle was a tool for survival,a shot fired probably meant meat to feed a family or a self defense situation against man or beast. A frizzen on a lock today must be made of something that will hold up to the use/abuse of todays sport shooters. We have today,a ready supply of good BLACK powder and hopeully,lead to mould a ball or bullet from which wasn't available to the rifleman and 1750. He had to ration his powder and lead was a precious metal for sure.
One thing is certain,most of the locks made today of the type we call pre-Revolutionary War are probably better for the way we shoot today than anything available in "The Days"
of old.
Merry CHRISTmas to all and my breakfast is ready.

Bob Roller

[Jim Kibler]

I've measured the case on a few original lock parts.  One was a Germainic cock that had broken and the case was clearly visible.  The other was a French cock that I was broken through the neck.  The depth on the original parts I've checked have been somewher around .020-.025" give or take a little.    Again, I think the base material being wrought iron must be considered.  At these depths the case adds considerable overall strength to the part.  Extremely thin sections should be drawn back to a higher temperature than the rest of the part.  

I might also suggest looking at the case hardening processes the Colonial Williamsburg gunshop has used.  JHAT indicates they used a hold time of 4 hours, but I believe they have cut that back considerably in more recent years.  I believe to the range of 1.5 - 2 hours.  Although it depends on temperture used, I would expect this hold time would produce a case somewhere in the vicinity of .020-.025".   Frizzens are held considerably longer.  Wrought iron is typically used as a base material.

Personally, I typically hold parts (plate, cock, top jaw, top jaw screw) for around 1.5 hours at around 1550F.  When carburizing a frizzen, I increase the hold time to around 3.5 hours and heat at around 1625 F.  I temper the entire cock, plate, top jaw, top jaw screw at maybe 450 F and then very thin areas I temper with a torch  to at least a blue color.  I'm sure I could get away with less case  using steel as a base material.  With the frizzen the idea is to drive the carbon deep for durability.  A carburized frizzen produces excellent sparks. With this temperature and hold time, a case in the range of .035" should result.

I've measured many case depths on carburized parts in my time.  I try not to mention this too often, but I am (was) a metallurgical engineer.  I worked for a facility that carburized parts primarily for the GM 6 speed automatic transmission.  Checking depths is really a simple process.  Section the parts, grind to say 320 grit or so.  Etch in a 20% Nitric acid water solution for a minute or two and it will be clearly visible.

One important last point.  Case hardening even, at home, is a very doable process.  It doesn't require a lot of high tech expensive equipment.  See the post from Acer.  I think it's important in the end to not lose sight of the fact that this work was often originally being done in relatively primative conditions in comparison to what we view as a controlled process today.

Enough!  Off to see the family.  Merry Christmas to Everyone

Jim

[Dphariss]

I've measured the case on a few original lock parts.  One was a Germainic cock that had broken and the case was clearly visible.  The other was a French cock that I was broken through the neck.  The depth on the original parts I've checked have been somewher around .020-.025" give or take a little.    Again, I think the base material being wrought iron must be considered.  At these depths the case adds considerable overall strength to the part.  Extremely thin sections should be drawn back to a higher temperature than the rest of the part.  

I might also suggest looking at the case hardening processes the Colonial Williamsburg gunshop has used.  JHAT indicates they used a hold time of 4 hours, but I believe they have cut that back considerably in more recent years.  I believe to the range of 1.5 - 2 hours.  Although it depends on temperture used, I would expect this hold time would produce a case somewhere in the vicinity of .020-.025".   Frizzens are held considerably longer.  Wrought iron is typically used as a base material.

Personally, I typically hold parts (plate, cock, top jaw, top jaw screw) for around 1.5 hours at around 1550F.  When carburizing a frizzen, I increase the hold time to around 3.5 hours and heat at around 1625 F.  I temper the entire cock, plate, top jaw, top jaw screw at maybe 450 F and then very thin areas I temper with a torch  to at least a blue color.  I'm sure I could get away with less case  using steel as a base material.  With the frizzen the idea is to drive the carbon deep for durability.  A carburized frizzen produces excellent sparks. With this temperature and hold time, a case in the range of .035" should result.

I've measured many case depths on carburized parts in my time.  I try not to mention this too often, but I am (was) a metallurgical engineer.  I worked for a facility that carburized parts primarily for the GM 6 speed automatic transmission.  Checking depths is really a simple process.  Section the parts, grind to say 320 grit or so.  Etch in a 20% Nitric acid water solution for a minute or two and it will be clearly visible.

One important last point.  Case hardening even, at home, is a very doable process.  It doesn't require a lot of high tech expensive equipment.  See the post from Acer.  I think it's important in the end to not lose sight of the fact that this work was often originally being done in relatively primative conditions in comparison to what we view as a controlled process today.

Enough!  Off to see the family.  Merry Christmas to Everyone

Jim

Citing case depths on broken parts is not a confidence builder.
Nor is annealing a way to maintain colors if that is the goal.
While its normal to heat parts to 350-380 to make them a little less likely to break this is about as high as can be done without color change. Hardened and polished frizzens heated to 375 by my oven thermometers (2)  show a pale gold color.

It is somewhat aggravating that so much of this stuff was not written down back in the day. But then and even into the early 19th century a lot of metal forging etc was done by eyeball (this resulted in about 1 million 03 Springfields being deemed unsafe to shoot, by the Army, the Marines kept using them).
And people to this day are often a little reticent in giving away their techniques.
 

Dan

[Jim Kibler]

Hi Dan,  Hope you had a Merry Christmas.  I anticipated the take on the broken part case depths  Why they broke is pretty uncertain.  The one cock is extraordinarily thin and I think this might have had something to do with it.  Perhpas he should have drawn it back a bit  When I find it I will post some photos.  The other I think may have been intentionally broken as both of a pair were broken in the same spot.  I think these pistols were in France during Nazi occupation and as I understand it, the practice of disabling firearms in such a manner was common.  Who really knows however.  

As far as colors go, I could care less about them.  I don't like them nor do I think they are appropriate for 18th century or earlier work.  Also, "annealing" is far different than tempering or "drawing back".  You may want to look this up

This I think sums up case hardening on modern steel locks for the plate, cock, top jaw and top jaw screw:
None works fine
A little works fine
More works fine as well
It all really isn't that critical
There are many things much more important to be concerned with  
(Reference my previous posts in this thread to find a similar take)


I did happen to find a historical reference to hold times in "The Gunmaker and Gunstocker" by PF Sprengel, Berlin 1771.  Sprengel indicates a hold time of one hour in "glowing coals".  The temperature is somewhat ambiguous by this description.  It seems reasonable that it would be greater than 1500F.  With this temp and hold time I would guess a case in the range of .015" might result?  I'm sure there was significant variability in period practice.

Interestingly enough, Sprengel also makes mention of the use of wrought iron for all parts other than the springs.  I have been questioned in the past concerning the historical use of wrought iron for frizzens and this text backs this up.  

Jim

[Bob Roller]

Just WHAT was available in the 18th century and earlier that would make a reliable mainspring or other springs for that matter?

Bob Roller

[Tony Clark]

Just WHAT was available in the 18th century and earlier that would make a reliable mainspring or other springs for that matter?

Bob Roller

Well Bob they did have the capability of making steel that was sufficient for springs in the 18th century. If I'm not mistaken the technology for making cast steel in this time frame of sufficient quality to make clock springs was being developed. Don't discount the suitability of shear steel for springs. Steel which was suitable for the durability of swords  was made for centuries before this, in fact the technology required in sword making for centuries before this had to be reinvented it was and still is somewhat a mystery. 

[Jim Kibler]

Just WHAT was available in the 18th century and earlier that would make a reliable mainspring or other springs for that matter?

Bob Roller

Bob, 

Here is a link to Gary Brumfield's website that has a good description of steel production during the time period in question.

http://www.flintriflesmith.com/WritingandResearch/WebArticles/ironandsteel.htm

[Dphariss]

Just WHAT was available in the 18th century and earlier that would make a reliable mainspring or other springs for that matter?

Bob Roller

Iron was smelted in a charcoal furnace and this actually made steel as it took on carbon from the charcoal.
It was then remelted in a different design furnace to burn off the carbon and other impurities.
Then a long soak in a closed container in a furnace or forge with charcoal to make blister steel that could be used for springs etc. But usually it required some work as iron bars, heating and hammering, to further purify it.
Dan

[Dphariss]

The comments on the broken tumblers are interesting. Something I had not thought about but is logical.
Greener talks of locks with steel sears and tumblers by the 1820s and 1830s.



It can be difficult to determine if parts were left colored or not. But I suspect most were shiny, that is the conventional wisedom for the 18th century.
But colors were left on by some makers in the 18th century in Europe at least.
But I can't find the citation.
By the same token even today color is generally not wanted on engraved steel
If casehardening is done with the right charcoals its hard not to get color.
So its pretty obvious that it existed in well before the 18th century. Its being polished off or not is another question.
I don't think there are enough pristine American made arms from the 18th century to make a statement one way or the other.
Like many things its not mentioned one way or the other. By the 1830s or so case hardening in colors was common.

So far as hardening and durability. It was necessary to replace the lock on "Drewyer's rifle" during the L&C expedition, it being too worn for use. So we have to wonder what hardening process those Harpers Ferry locks went through and how effective it was. Was the lock make with steel internals or iron.  Were they through hardened and tempered or cased.
I suspect cased but as you point out the process was eyeball and the parts might not have been soaked long enough. But we have no details on what wore out. They had spare parts so I assume the lock was not worth fixing and it was easier to put in a replacement lock.  In any case the hardening was faulty I would think. It would  take a lot of use to wear out a well hardened lock. But material quality might have been a factor.
I would love to know the wear patterns.....
Dan

[Bob Roller]

Many thanks for the info on the steel making of the 18th century. It gives me a new respect for what our ancestors had to do to obtain a useful material.
The idea of case hardening a lock plate may have merit. Years ago,I had a lock to come back that died from stupidity and neglect which to me are identical twins. The upper bridle screws had worked loose from years of firing and no checking or maintainance and the tumber hole in the plate had worn into an egg shape as had the bridle bearing hole. I was able to restore them by reaming oversize holes and installing bushings in both. Neither the plate or the bridle were case hardened but I did make the bushing from oil hardening drill rod which made a nice fix.

Bob Roller

[Tony Clark]

Many thanks for the info on the steel making of the 18th century. It gives me a new respect for what our ancestors had to do to obtain a useful material.
Bob Roller

Bob I'm hoping you read Gary Brumfields write up on iron & steel production in colonial America as it correctly explains the processes used. The technology to melt iron or steel was not available here in the U.S. until it was introduced by Bessemer in the 1850's, so the only way steel could be produced was by taking wrought iron and basically case hardening it to produce what was called blister steel. This was not suitable for springs it being the lowest grade available. But blister steel could be cut (sheared), stacked and forge welded to produce what was called shear steel. This made the steel more uniform throughout and further removed impurities by the hot working of it. This process could be repeated several times or more. Shear steel could be used for tools, knives, springs, razors etc. Shear steel was marked "shear steel" and a numerical designation such as 2, 3, 4, 5 etc which referred to how many times it had been cut, stacked and re-welded, the higher numbers meaning a better quality steel.