Lock plate brace

[holzwurm]

Gentlemen/Ladies

In preparation for doing a color case hardening of a lock (first time) I've been advised to brace the lock plate to prevent warping.  The question is, is the placement of the three screws OK for the task or should I add more? The backing plate is a piece of 3/32 CRS.

[Paddlefoot]

Should the brace be on the inside of the plate so the charcoal pack goes against the exposed side??  Other than that it looks good to me.

[holzwurm]

oops, forgot to show the other side of the brace. I took a page out of Jerry Huddleston's instructions and drilled a lot of holes through the brace so the pack will do its job of coloring the face.

[Paddlefoot]

OK, that looks familiar. Is there space in there for the pack so the quench just washes it out through the holes?

[holzwurm]

the lock plate is flush against the brace -  I think I read that as long as I have the vent holes in the brace, having the lock plate against the brace is OK.

Have I missed something - should I position the plate away from the brace a few thou's with a thin washer or something?

[Paddlefoot]

My understanding of the Gaddy article was that there was space in there and the holes washed out the charcoal pack but held it in position long enough for it to keep the surface surrounded by the gas as it entered the quench. I have not done any of this personally so I'm just trying to learn along with you.

[Paddlefoot]

You asked about control of the colors in the wire wrap thread. The Gaddy article talks about using a reducing flame from a small torch setup to adjust colors after the quench..

[Jim Kibler]

I have always used stand-off tubes to hold the plate off the stabilizing bar.  The bars I have used have been 3/8" thick or so.  The more points in which the plate movement is controlled the better.  Also, I think it's a good idea to pull the plate from the pack with an attached wire and quench vertically.  This is of course if colors aren't your goal.  A bent plate can be a real pain in the but.  I won't claim to be an expert as lately I've had problems controlling plate movement.  Good luck!

[David Rase]

I have always braced on the back side and used standoffs.  Looking forward to seeing the results of your efforts.  Plates warp when the come out of the pack and hit the water like a pancake.  You need to preplan the entry of your parts into the water.  As long as the parts enter the water edge wise you should not have any problem with warpage.
DMR

[Jim Kibler]

I have always braced on the back side and used standoffs.  Looking forward to seeing the results of your efforts.  Plates warp when the come out of the pack and hit the water like a pancake.  You need to preplan the entry of your parts into the water.  As long as the parts enter the water edge wise you should not have any problem with warpage.
DMR

That's what I thought too

[smart dog]

Hi Holzwurm,
I always brace my plates (unless they are small pistol size and don't need it) on the inside with spacers so I can place a wire wrap around the plate that touches the outside to be colored.  I also pack lockplates in steel pipe with a screw lid that is loosely attached and can be taken off easily.  By using the pipe, the entire pack comes out one end intact and hits the water vertically.  I hold the pipe only a few inches above the quench when pouring to prevent air hitting the parts before they hit the water.  Wear heavy elbow length insulated gloves, leather apron, and a full face shield.

[holzwurm]

well. . . . hmmm? Looks like I have to go back and start again.  I thank every one for thier interest in helping me out.

[Paddlefoot]

Smart dogs system sounds like what was in the Gaddy article. He described having a plate with wing like blades wired to the part and pack sitting above the parts as they are hearted. The plate had charcoal pack above it and a removable lid on top to keep the gasses trapped during the heating process.  The plate with the blades( I imagine it as sort of a pinwheel without the twist to the blades) pulls the treated parts out and introduces a bit of air and turbulence to the quench water as the parts follow it in. Gaddy also says the water was cooled to 45 degrees in order for it to hold as much oxygen as possible. Good luck Holz, we are interested to see how it comes out.

[44-henry]

I make a special plate out of .30 steel and have standoffs pressed behind the plate leaving about 3/16" gap between the plate and the block. The more the better in my opinion. Degrease the plate before mounting it on the block and than wrap in degreased soft iron wire to taste. If I get a chance I can post pictures of the rig I used last time an the results on a couple of plates I ran through. I think I have them stored on my other computer right now. My quench system drops the plates in the correct orientation as I pack them that way to start out with. If you create a cover on the bottom of block assembly that enters the water first (like a saucer) it will displace the water and you'll get better colors as the water will crash around the parts more uniformly from all sides and the charcoal will stay in contact with the parts longer. You'll get better colors on the sides of the plate that face the jig largely because the charcoal will be trapped in these areas longer during the quench. Hope that helps, good luck.

[David Veith]

Does anyone have a copy of Gaddy article. I would like to read it.
David

[Acer Saccharum]

I have always used a brace along the back, 1/4" thick stock, with three spacers to hold it away from the lock plate, at least 1/4" tall. Usually the spacer warps a little

Maybe I don't need to use the brace, but since I always dun it this way, I prolly allus will.

Parts tend to warp if there are changes in thickness. The thick sections take longer to shrink than the thin ones. An example would be a round faced lock with an integral bolster. The edges of the plate will freeze, and the bolster will still be hot and shrinking. This will curl the plate some, and set up internal stresses. It's probably wise to cook the parts after hardening at 350 degrees for an hour. This won't change the colors much, but it will help relieve some stress.

Casehardening a lock is one aspect that can develop a lock to its full potential.

Tom

[g.pennell]

Here's the Chambers early Ketland from my Virginia rifle we just case hardened this past weekend...2:1 wood to bone charcoal, heated to 1350 F for 2 hours, then reduced gradually to 1100 F for 30 minutes, then quenched in 45 F aerated rain water.  We packed it to hit the water vertically, no bracing, no detectable warping.  I still need to polish the frizzen spring and screws and nitre blue them.

Greg

[44-henry]

You can get nice colors under critical temperature, but they aren't well suited to hardening the steel. There was a thread on the Marlin forum some time back where somebody was recommending these low quench temperatures as a way to get enhanced colors without causing distortion to the action. This is all fine and good if the colors are all you are after and surface hardness is secondary, but on parts that need to be hard to provide good and safe service it is in my opinion a big mistake. If you anneal/normalize your parts before the casehardening operation, block them properly, and orient them correctly to hit the quench tank in the right way and keep the quench temperature above critical range you will have a lot less trouble with distortion and also will actually have hardened parts.  I try to keep my quench temperatures over 1400 F and less than 1500 F usually shoot for the 1450 range. This is not to say that I haven't experimented plenty with temperatures other than this, I just tend to find this range the most ideal.

How well does your lock spark?

[Jim Kibler]

To add to this a little further, if you don't care about colors even higher temperatures than 44-Henry suggested are beneficial.  This will result in a higher percentage of surface carbon since the solubility of carbon in iron is dependent on temperature.  In addition, the case depth will be increased for a given length of soak time by using higher temperatures.  For the vast majority of 18th century longrifles, I wouldn't consider case colors to be appropriate.  Soak temperatures in the range of 1600 or even a little higher and then dropping to 1500-1550 for quench is likely a good process.  Using these higher temperatures becomes even more important when carburizing critical parts such as a frizzen.  Just like some say they get away with using Kasenite on a frizzen, other procedures may seem to work ok, but I am suggesting they are not ideal.

[keweenaw]

Jim is right on about the difference between coloring and hardening.  If you are quenching from under critical temperature you can color but it won't appreciably harden the surface.  Many commercial cast lock parts are made of 8620.  The recommended carburizing temperature for 8620 is 1525.  One can lower the temperature to about 1450 after the soak and get a good surface hardness. 
As for bracing the plates, I never do it.  I use a tall crucible that stands vertically in the furnace and pack so that the plates hit end first into the quench tank.  No problems with warping.

Tom

[holzwurm]

This has been a very informatived string for me. Yesterday I welded up a crucible for my lock based on the dimensions of my electric oven - it's 6.25" tall which makes standing up a longer lock a bit of a problem, so I'm going to remake a crucible which lay's on its side where I have over 8" so I can color any length lock. I'll still be able to dump the lock into the water vertically, as has been suggested.

I have another crucible which will hold all the other small parts. I noticed that Greg (above) didn't color his friz, the friz spring and the cock top screw. Was there a reason fo this or are they too delicate to endure the heat range of the other stuff?

[JCKelly]

There are differences amongst: 1.) case-hardening a frizzen of some unknown steel, 2.) color hardening a KNOWN low-carbon steel, and 3.) color hardening a modern investment cast lockplate, again of quite unknown grade.

The highest carbon in the case does NOT come from the highest temperatures (the iron-carbon diagram says the solubillity of carbon in austenite increases with temperature. True but that is not the whole story here.)

First, though not this thread: Modern AISI 1095 carbon steel contains about 1% carbon (strictly speaking, the specified range is 0.90 - 1.03 % carbon)  Nicholson American-made files, a couple decades ago when I dealt with their heat treat, are of 1095 steel. Rightly or wrongly, this grade is, so I have heard, a common modern choice for investment cast frizzens. To harden 1095 Nicholson heated their files at 1440F and quenched straight down into salt water. Heating higher does nothing good. So, if you have a cast 1095 frizzen & wish to harden it, heating 1440F is as high as you need go, assuming reasonable temperature control. Color case hardining a low-carbon steel frizzen, will, in my humble opinion, give a frizzen with very short life. Too shallow a case, like we all get with good ol' Kasenit (heresy!).
Second, color-hardening per Gaddy does give a thin, maybe 0.002" thick, and hard surface even though he hardens about as low as one can go, just above the critical point, Ac. This is of no modern commercial importance, as for modern machine components, such as gears, the CORE hardness is also important. Color hardening is done at a relatively low temperature, so that only the high carbon case will harden, while the core remains soft.
Third, color hardening an unknown modern steel. If you are color-hardening a patent breech it is a very a good thing for only the case to harden, leaving the core soft. Color-hardening should give enough of a case to prevent scratches. Likewise enough case so the lock-plate is srviceable.

Modern procedures for case-hardening 8620 should be applied only very carefully to muzzle-loading gun parts.

And finally, my apologies for leaving out page 10, Winter 1996 Gaddy article to all those who got it from me. Will correct this.

[Jim Kibler]

JCKelly,

Virtually all period frizzens were made from wrought iron and case hardened.  Ocasionally you will find one faced in steel.  Carburizing a low carbon frizzen works quite well, provided a high enough concentration of carbon and depth is obtained.  Some of the best at producing locks feel the results of a well carburized wrought iron or low carbon steel frizzen are superior to a through hardened high carbon frizzen.  So with this the case, higher temperatures and soak times are important in obtaining both carbon concentration and depth.  As to the remaining lock parts which are generally carburized, I feel a depth greater than commonly obtained with color case hardening temperatures are important as well.  Total case depths of .040-.050 aren't necessary as in the case of a frizzen, but the few thousands resulting from processes using lower temperatures are not sufficient in my opinion as well.  Personally I could care less about colors.  I will try my best to select a process that produces the most suitable part.

[JB2]

lots and lots and lots of good info here!  Makes me wanna buy a kiln!

[Paddlefoot]

Just bought a Davis lock and in their paperwork there was a section on Kasenit hardening the frizzen if needed. Their explanation said to use the Kasenit on the frizzen following their instructions as it would cause the steel to form finer grain structure that would make better sparks than traditional methods. Their explanation was that the metals used in modern investment castings were closer to tool steels and would tend to form larger harder crystal structure that would be too hard for a flint to scrape for good sparking.