A bastard file is a file whose teeth configuration is in between a rough or coarse file and a 'second cut' file. In precise terms therefore a bastard file is one which 'is one cut finer than that of a coarse file'.
In common language a bastard is an illegitimate child, one born out of wedlock. However it may also allude to something that is unusual, irregular or disproportionate. It is this latter meaning that is employed in the term bastard file, not the former.
Dictionary etymologies for the term 'bastard file' are virtually nonexistent, but a plausible explanation is obtained from the meaning and use of this kind of file. In this context the word bastard alludes to a rather irregular file, in other words, referring to a file that can neither be classified as a 'coarse file' or as a 'second cut file'.
In common language a bastard is an illegitimate child, one born out of wedlock. However it may also allude to something that is unusual, irregular or disproportionate. It is this latter meaning that is employed in the term bastard file, not the former.
Dictionary etymologies for the term 'bastard file' are virtually nonexistent, but a plausible explanation is obtained from the meaning and use of this kind of file. In this context the word bastard alludes to a rather irregular file, in other words, referring to a file that can neither be classified as a 'coarse file' or as a 'second cut file'.