hammer away at (something)
1. To strike something repeatedly The mechanic hammered away at the dent in my door. I hammered away at the beef with a meat tenderizer.
2. To work hard on something persistently over time. Yes, we're still hammering away at the details of this contract.
3. To talk about something at length, often to the listener's annoyance. Quit hammering away at that topic—no one wants to hear about it anymore.
hammer away at
Keep at something continuously, as in The reporters hammered away at the candidate. This phrase employs hammer in the sense of "beat repeatedly," a usage dating from the mid-1600s.