drilling bit vs drill bit

drilling bit and drill bit both are nouns.

Word	Noun	Adjective	Verb	Adverb
drilling bit	Yes	No	No	No
drill bit	Yes	No	No	No

As nouns, drilling bit and drill bit are synonyms defined as:

drilling bit (noun)	drill bit (noun)
a bit used in drilling for oil	a bit used in drilling for oil