[TheForge] File Making

[Chuck Robinson]

The smith is using a high temp salt bath about 1550 F to bring the file to 
critical heat.
 He is then coating the surface with a compound that is adhering in the 
recesses of the file teeth.
Next step is back into the salt bath to critical temp again. If you compare 
the file color to the salt color they are the same temperature. some where 
out of sight is a temperature controller keeping the salt at critical temp.
Every sharp hollow in the file is a stress riser that could crack with the 
near instantaneous shrinking of the file as it changes from austenite to 
martensite.during the water quench. The compound is used to slow the cooling 
in the hollows to prevent cracking.
Chuck