Hardening a Davis lock tumbler?

[Hemo]

Perhaps there is a previously posted link on this subject, but I couldn't find specific info on this site. I am close to the end of a build using a Davis Jaeger lock. I've had this lock sitting around for over 25 years and finally found a project to apply it to--an early 1700's Dutch/German flint pistol, built up from a blank. (Yes, it's a big lock for a pistol, but it's a pretty big pistol.) Getting around to final lock re-assembly, I found the half-cock spur on the tumbler was almost totally broken off. I got a replacement Davis tumbler, new, from TOW. A few slight design differences are present over the past 25+ years, but it appears to be a good part. However, I found it was fairly easy to cut with a file, meaning, I presume, it is not hardened. My question is, do I need to harden this part, and if so, what is the best method? I don't have an oven for heating, but do have a little oxy-acetylene torch and could probably bring it up to appropriate temperature by grossly eyeballing the color. But then, how to quench? Water, brine, oil?  Or should I case harden with Casenite or some some similar means, or heat in charcoal, or leave un-hardened? Any guidance is appreciated!
 
Hemo

[Mark Elliott]

It should be hardened,  and they ARE made of hardenable steel.  Don't try to case harden them or you are likely to crack them if you quench in water.   Your torch and kitchen oven will probably work Ok.  The way I handle tumblers, flys and sears is the same.    Heat evenly to a bright red, not quite orange, in normal room light and then quickly quench in oil.    Keep the part moving in the oil, don't just let it sit there.  One quart of 20W motor oil will be fine.   Check the hardness with a file to make sure it got hard in all the wear spots.  I then temper to 500 degrees.   I think your kitchen oven can probably get there.     You want to bring up to temp and hold for at least 30 minutes.   Then just let the part cool.    I have heat treated parts from Chambers, Davis, and L&R and the preceding worked Ok. 

[Hemo]

Thanks,Mark, that was very helpful!

Hemo

[Mark Elliott]

I should note that the part should be bright red when it hits the oil.   That means that it will probably be a salmon color, but not too bright, when you start to make the trip to the oil.   The problem with small parts is that they cool off quickly in air.   Really small/thin parts will air harden even in non air hardening steel.   You shouldn't have a big problem with the tumbler cooling off too fast.   I just wanted you to be aware that it is the temperature of the steel when it hits the quench medium that matters.   That said, you still don't want to heat the steel more than is really necessary to get the job done for all sorts of reasons.    I suggest that you use a carborizing flame for the heating.