hammer at (something)
1. To strike something repeatedly The mechanic hammered at the dent in my door. I hammered at the beef with a meat tenderizer.
2. To talk about something at length, often to the listener's annoyance. Quit hammering at that topic—no one wants to hear about it anymore.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
hammer (away) at someone
Fig. to interrogate someone; to ask questions endlessly of someone. The cops kept hammering away at the suspect until he told them everything they wanted to know. They hammered at him for hours.
hammer (away) at something
1. Lit. to continue to do a task that requires much hammering. The roofers are hammering away at the job, trying to finish before night.
2. Lit. to pound at or on something, such as a door. Who is hammering away at the door? The police are hammering at the door.
3. Fig. to dwell overly long on a point or a question. Stop hammering away at the same thing over and over. The agents asked question after question. They would not stop hammering at the issue.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.