Kutter, Just curious, how did you get color without hardening? Or is that what you were saying when you did touch-up with a torch?
Dave
The combination of the furnace temp, furnace time and quench temp could be adjusted to produce the same colors with either no hardness or with a case hardened surface.
Everything else stayed the same in the process as far as the little things go like the time it takes to go from the furnace to the quench, the drop distance (very important in getting colors or not), the mix ratio, drying the char out before using, box size, etc.
Most of the work early on was directed towards the colors and not hardness. This was in the late 80's, very early 90's. Warpage was a problem up untill that time and so was extreme case depth on some parts. Once the warpage problems were under control (by elliminating the hardening for the most part!), a marketable service was at hand. The fact that little or no case depth was present was of little thought as most all the guns done were collectors pieces and not shooters guns.
With little problems in the area of warpage or other damage, the guns assembled easily though as I said the colors were 'soft' and easily worn. It soon became apparent that colors alone wouldn't suffice as some heavily used guns such as those from clay target shooters and the new Cowboy Shooters sport were having problems with galling.
The case hardening was for a reason,,the colors are a gift!
One large customer, a custom shotgun mfg'r, went ahead and set up & did his own CCH process for his guns in the mid 90's to avoid those problems he was receiving.
More adjustments to the process to put some hardness back into the parts was done. They never completely satisfied what I would have wanted but then no one asked me for my opinion.
Some parts don't need any hardness,,some probably shouldn't have any.
Some of the modern gun steel previously HT'd frames being done shouldn't be done at all, but again that's just my opinion.
Some steel is case hardenable,,and some steel is non-case hardenable. Seems like an easy enough thing to sort out but that fact is not followed through many times and modern alloy steel parts are done to 'color' them with small regard to what's done to their structure sometimes.
The torch touch up is just that,,a occasional part taken out of the case color process with little on it other than the basic grey background color and maybe a few scattered spots of blue. You can add color to it if you quickly get at it while still hot from the quench water (probably 170F+ as a guess) and carefully use the small tip to add a few clouds of color to the blank areas. Easy to spoil it though!,,as it takes only a second or two to work once the tip/flame meets the surface.
You may be surprised at how many older case colored guns were not hardened also. Some of the older guns I've worked on had no hardness, only colors to the frames. Seems especially true on European shotguns from between the Wars for some reason but others too. Beautiful colors,,no hardness.
Hope this all helps or at least is of interest..
