Case hardening and case coloring

[Joe S.]

very ņice, perhaps a way of keeping the screws in the tang while in the heat would give them the color you seek,more mass better to absorb the heat.Probably dummy blocks giving them the mass so you can still block the tangs would be better.

[flatsguide]

Dave,
Those colors look just fine. I think I would just fire blue the screw heads. Was there any warpage to speak of?  I am curious about hardness. From what I understand, the more carbon in the steel, the lower the quenching can be and still get an increase in hardness. Adding carbon to the surface via packing in charcoal may raise the carbon point high enough to get the desired hardness at a lower , 1400 degrees in this case, temperature. I think Jim Kibler is a metallurgist. Would be nice if he could chime in.
Regards, richard