Lock kit building

[Bob Roller]

The machines and the filing are very compatible. I watched George Killen hand file a lock tumbler from a barge deck bolt.I never tried to do that and realized the value of machines early in life.I used the machines to the extent possible and then the fine details were filed in accordingly.No low end files needed or wanted.
Bob Roller

[Clint]

If you decide to build a lock from a casting set, give some thought as to exactly which lock set you buy. Locks that are smaller than five inches in length are more difficult than musket size locks. 5 inch rifle size locks can be made with #6 screws but be prepared to use #4's in tight spots. Most of the cool lock sets are made directly  from originals and there will be a tiny bit of shrinkage because of the cooling of the casting. This shrinkage is barely noticeable on the finished lock. HOWEVER, the main disadvantage of working from a direct casting is that the original lock was fitted, drilled, tapped and then finish filed. You will be starting with the finish filed version, so you need to be very careful with hole locations. Having said that, it is eminently possible to put casting sets together and end up with a cool, perfectly useful lock. I have built a couple dozen locks from casting sets and many from scratch, I still consider my self a student lock maker and I do it ,mostly for fun.  CW

[Clark Badgett]

What would the ideal hardness be for a tumbler?

If you don't have a Rockwell Hardness Tester to test the part, then the Rockwell Hardness number means NOTHING - it's is just a number. It's like saying "how hard is hard"? You will need to reference a color chart to get you in the ballpark for the steel you are using. This goes for the initial hardening temp and tempering temp also. You do not want the part to be so hard as to chip or fracture nor too soft as to deform the half or full cock notches when used. Make up test pieces and try cutting them with a good fine file this should give you an idea on how hard your part is.
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I am a machinist, so I do have access to a couple of testers. I also have access to a proper temperature regulated oven. That's why I asked the ideal hardness.

[Bob Roller]

Hardness is a number.My own criteria is a lot of locks all over the world and no reported problems.
I have not really tried to assemble any locks from prefabricated parts and know that casting techniques
have made quantum leaps but they are very costly and the very limited market that caters to muzzle
loading guns is just that,limited and supported mostly by individual hobbyists with mostly limited means.
Most of us do what we can with what we have and are glad to see whatever success we get.
Bob Roller