countersink bit vs countersink

countersink bit and countersink both are nouns.

Word	Noun	Adjective	Verb	Adverb
countersink bit	Yes	No	No	No
countersink	Yes	No	Yes	No

As nouns, countersink bit and countersink are synonyms defined as:

countersink bit and countersink: a bit for enlarging the upper part of a hole

Other synonyms of countersink bit include counterbore.

countersink bit (noun)	countersink (noun)
a bit for enlarging the upper part of a hole	a bit for enlarging the upper part of a hole
	a hole (usually in wood) with the top part enlarged so that a screw or bolt will fit into it and lie below the surface

countersink bit (verb)	countersink (verb)
	insert (a nail or screw below the surface, as into a countersink)