Used this for 8 hrs three days in a row busting out concrete. Loosening boulders out of concrete perches; breaking stem wall around rebar. Must add oil before use, and I greased up the chistle on the machine end. One review said it hammers for a bit and then just vibrates. Happened to me as well, I just gave it a little more down pressure or raised and rammed it home again. This thing is a beast. Highly recommend. Hundred bucks cheaper than Harbor Freight and Lowes and the delivery was actually a bit early.