I'm in need to buy a rotary hammer to make some holes in a slab about 12 cm thick of armed concrete. The holes will be between 5 and 10 cm in diameter, so I will have to hammer a round opening instead of drilling through (or drill lots of holes in a circle).
The rotary hammers in the market goes from 2,5 to 30J. I have no idea of how much energy I need to this task and I wasn't able to find it anywhere. The price goes up really high (and so is the weight of the tool).
The smaller models (about 2,7J) like Bosch GBH 2-24 costs about 7 days of rental of a bigger model (about 10J), so I'm inclined to buy one if it will work.
Best Answer
It's mostly going to be about speed - if you are patient and like handwork, a star drill and 4 lb / 2 kg hand sledge will drill holes in concrete or granite. If you plan to drill many small holes and then hammer out the plug, the smallest rotary hammer drills will generally do that just fine. The bigger ones may do it much faster, and will do it with bigger bits.
The "nice way" to drill finished holes of the size you want is with a core drill (which just drills around the edge, like a hole saw, leaving a plug or core) but those cost serious money even to rent/hire, usually.