go at vs hammer away

go at

verb
  • To try to solve a problem a specific way; to undertake a task. 

  • Used other than figuratively or idiomatically: see go, at. 

  • To initiate an attack on or an argument with. 

hammer away

verb
  • To continue discussing (a subject) or trying to solve (a problem). 

How often have the words go at and hammer away occurred in a corpus of books? (source: Google Ngram Viewer )