expansion bit vs expansive bit

expansion bit and expansive bit both are nouns.

Word	Noun	Adjective	Verb	Adverb
expansion bit	Yes	No	No	No
expansive bit	Yes	No	No	No

As nouns, expansion bit and expansive bit are synonyms defined as:

expansion bit and expansive bit: a bit with a cutting blade that can be adjusted to different sizes

expansion bit (noun)	expansive bit (noun)
a bit with a cutting blade that can be adjusted to different sizes	a bit with a cutting blade that can be adjusted to different sizes