"He who marches out of step hears another drum." ~ Ken Kesey
Against my previous advice (because he knows exactly what he's doing) if you're bummed because of the investment you've made in him by giving him a chance, call him in, tell him you've watched this behavior for some time now, and that there won't be another discussion about it. One more time clock error, one more clocking out after standing around, one more clocking in at 7:40 then goofing off until 8, and he's out with no opportunity to explain.