metal filing vs filing

metal filing and filing both are nouns.

Word	Noun	Adjective	Verb	Adverb
metal filing	Yes	No	No	No
filing	Yes	No	No	No

As nouns, filing is a hypernym of metal filing; that is, filing is a word with a broader meaning than metal filing:

metal filing (noun)	filing (noun)
a fragment of metal rubbed off by the use of a file	preservation and methodical arrangement as of documents and papers etc.
	the act of using a file (as in shaping or smoothing an object)
	the entering of a legal document into the public record
	a fragment rubbed off by the use of a file