1) Argue in too much detail 2) Beat a dead horse 3) Beat soundly 4) Beat to death 5) Beat to death, so to speak 6) Belabour 7) Dwell on 8) Dwell on excessively 9) Excoriate verbally 10) Explain ad nauseam 11) Explain excessively 12) Flog a dead horse 13) Go on and on with 14) Harp on 15) More than hammer home 1) Beat 2) Belabour 3) Harp on 4) Overdo 
• (v. t.) To beat soundly; to cudgel. • (v. t.) To ply diligently; to work carefully upon.
Be·la'bor transitive verb [ imperfect & past participle Belabored ; present participle & verbal noun Belaboring .] 1. To ply diligently; to work carefully upon. 'If the earth is belabored with culture, it yieldeth corn.' 
beat hard 
[v] - to work at or to absurd length 2. [v] - attack verbally with harsh criticism
belabor 1. To repeat or to discuss something unnecessarily or at too great a length. 2. To discuss something repeatedly; to harp on and on without stopping. 3. To subject someone to a sustained verbal or literary attack.
belabour verb to work at or to absurd length; `belabor the obvious`
to explain, worry about, or work at (something) repeatedly or more than is necessary: He kept belaboring the point long after we had agreed. · to assail persistently, as with scorn or ridicule: a book that belabors the provincialism of his contemporaries. · to beat vigorously; ply with heavy blows. · to labor at.