chisel in

verb2

1. •
   To barge in on something; to be a third wheel; to insinuate oneself into a situation or relationship; to get oneself involved in something.

   • Ignore him, he's only here because he chiseled in.
2. •
   (slang) To unfairly push in on (something); to gain a role in (something unsavory); to acquire a partial interest in (something) through deceit.

   • He's chiseling in on our operation.