One addendum to the otherwise excellent idea of breaking a file to use as a fine grain standard: it has to be a solid steel file, not one of the cheaper case hardened files. So, either an expensive file or a very old file preferably with a major name like Nicholson or Grobet. But, any kind of file will do if it meets that criteria be it mill, bastard, rasp or whatever ...
Last edited by Ray Rogers; 12-31-2016 at 08:26 AM.
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