Quick floor check with a known file: if the file skids instead of cutting, the surface is file hard, roughly above 58 to 62 HRC depending on the file. Calibrated test files are sold in sets for specific HRC levels and used on parts that cannot go on a Rockwell tester, such as large gears and assemblies. A file check shows only surface hardness, not case depth.
Ran a file across the bearing seat and it skated, it's file hard, so the carburize took.
Also heard as
- file-hard
- skates a file
Related terms
Rockwell hardness
The standard shop hardness test that presses a diamond or ball into a part and reads depth as a number.
Glass hard
Fully hardened and untempered, so hard and brittle that a file skates off and a drop could shatter it.
Case
The hardened outer layer of a case-hardened part, as opposed to its softer, tougher core.
Decarburization
Loss of carbon from the surface of steel during heating, leaving a soft skin that will not fully harden.