Case Hardening a Lockplate

[SingleMalt]

I purchased Chamber's Golden Age Gum-makers lock for an upcoming project. After shaping the lockplate, I'd like to case harden the lockplate, cock, and screws.

We've all heard of lockplates warping when quenching. My question is, how heavy a piece of steel should I attach the lockplate to?  I plan to use two MAPP gas torches, so it can't be too thick. I was thinking Home Depot angle iron.

Thanks in advance.

[bob in the woods]

You must be using an equivalent to kasenit if you're using map torches ??   

[SingleMalt]

You must be using an equivalent to kasenit if you're using map torches ??

That's the plan.

[Hungry Horse]

Since you're not color case hardening, and are using Mapp gas torches, I must assume this is going to be a light surface case hardening. If it's just a surface case, you can slip the plate into the quench edge ways to minimize any warpage, and since it is only surface hardened, hammer it straight. You may not get much, if any warpage at all.

  Hungry Horse

[rich pierce]

HH is on the money there.  It's pretty safe hammering lockplates.  I have a copper hammer for such tasks.

[L. Akers]

I have done several lockplates using a compound I bought from Herter's a million years ago.  I use a "furnace" made from a clay flower pot and a Mapp gas torch.  I plunge the plate into the quench edge-wise and have had no problem with warping.  You may be able to get some "pattern" if you bubble air through the quench and plunge the plate into the stream of bubbles.  I use a bait bucket aerator.

[SingleMalt]

OK...  When it's done, should I draw it back to to what color?

[bob in the woods]

The reason I asked is that I have never had a problem with the surface hardening [ kasenit] compound  ref: warpage.
These days, I mostly use it for screws and such.  Deep case hardening with a crucible, bone meal, charcoal etc is another story.
When surface hardening with a torch and kasenit I don't " draw back" the piece . I just leave it as is.

[Bob Roller]

The reason I asked is that I have never had a problem with the surface hardening [ kasenit] compound  ref: warpage.
These days, I mostly use it for screws and such.  Deep case hardening with a crucible, bone meal, charcoal etc is another story.
When surface hardening with a torch and kasenit I don't " draw back" the piece . I just leave it as is.

I used Kasenit and quenched in 5 gallons of distilled water heavily altered with one pound of
potassium nitrate.Heat source was #5 tip on a Presto Lite "B" system and it worked fine and
Kasenit will make some nice color which Cherry Red will not do.
I wear eye protection because there are times when this method will sound like a gun going off
and will blow the Kasenit off the piece being hardened. I used this method for years until I found
that Kasenit was becoming extinct.

Bob Roller

[Joe S]

OK...  When it's done, should I draw it back to to what color?

The steel you're working with does not have enough carbon in it to harden.  That's why you added carbon to the surface. So, no need to temper it, but normalizing the plate is a good idea.  Heat to dull red, then put on your workbench to cool.

[bob in the woods]

Sorry for asking but...if you heat it up to dull red and then put it on the bench to cool, won't you be "undoing" the surface hardening you just worked to attain??

[rich pierce]

After case hardening, do not temper or normalize. Surface carbon does no good if the lockplate is soft.

[Joe S]

Yup.  You're right Rich.

[Old Ford2]

Heating a flat piece of mild steel to a cherry red, then quenching it into different oils, ie: peanut oil, canola, transmission oil, and used motor oil will give to durable colors.
But you only plunge the flat plate into the various oils part way.
What I mean is to plunge one end in partially ( into one type of oil ) then the other end reheated the plunged partially into another oil, and then again for the upper of the plate into another oil, and the same for the bottom. You must heat after plunging into each oil.
You will be surprised the different color of blue that you will get.
If you are afraid of messing up your lock plate, practice with an ordinary piece of mild steel.
You will not harden the lock plate to any degree, but you will get multiple blue colors.

[James Wilson Everett]

Guys,

To minimize the chance of a part warping when heat treating:

1.  Do not heat the part from one side only, try to heat evenly from both sides (a bit difficult when using a torch as the heat source).

2.  Quench the part by plunging it straight down into the quench liquid, do not swirl or stir the part in the liquid, just plunge it in and hold it still.  Swirling the part may cause one side the cool at a different rate than the opposite side, resulting in warping.

3.  A flat part, such as a lockplate should be plunged into the quench liquid vertically, as if the gun was aiming straight up.

[RAT]

Just an informational question... what type of steel does Jim Chambers use for his lock plates? I found an old hand written note to myself that it's 8620.

[David R. Pennington]

I case hardened a Chambers lockplate (Casenite) and it warped a little. I straightened it in vise jaws with some heavy leather pads. I put a piece of leather on each end on the concave side and a piece in the middle on the convex side and squeezed it back straight with the vise.

[Long John]

I case-hardened a Chambers lock recently.  I use a piece of 3" diameter, schedule 40 pipe with a steel cap as a crucible.  I just packed the pipe with the lock plate vertical, no backing plate, so when I dumped it into the water it hit like James W.E said to do and there was not warping at all.  I guess I got lucky!

John Cholin