I do believe that could happen! But I am using what I think are a little better quality case harden file and I have moved to the more aggressive 'General Purpose' file with large double cut teeth which is less susceptible to breakage even using it for filing very hard metal.

I have also read the thoughts of teeth possible breaking off and have inspected the files several times for that possibility. One thing that could lead to the teeth breaking is if the files are rubbed against each while knurling or if the files were stored loose against each other. Keep the files away from each other

Also you can see in the picture I do use a leather pad under the bottom file for a cushioning effect.


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Another thought I have is the metal that I am knurling is not that hard and the knurling really does not go deep. Even the brass bullets I am knurling accept the knurling to a certain point.


Lee, at this point I have not seen any indication that file breakage might be occurring.