I guess it is time I elaborated on "A hammer drill, by design, will self-destruct". This is especially true for light-wieght designs. And even well made hammer-drills will not last for-ever, especially if not properly used. Many people just abuse them, or use them far past thier abilities, or design. Using cheap, or dull bits, is a common no-no. And even though they make a 3/4" masonary bit (intended for soft brick) that will fit in a 1/4" chuck, I see people using them on hardend concrete and burning through rebar, or should I say attempting to.
To me a cordless hammer drill is just invitation to buy more tools. Lightwieght plastic casing, or worse plastic gears with a metal piston bouncing back and forth. These drills are only barely designed for an occassional 1/4" hole. Using one all day for larger holes is tool suicide.
A Bosch Bulldog with the proper hardend and sharp bit will run all day for for 1/4 - 3/8" holes. But use a cheapo bit, or a good but over-used one, the effeciancy goes way down. You then have a drill working harder, and over-heating, especially on hardened concrete with aggregate. Stick 3/4" - 1" bit in it and you're over working it.
Now go to the Rotor hammer and put a dull 3/4" bit in it and you'll have to rest the drill before the thermals kick in and it shuts off anyway. A good bit allowing the drill to do the work and you're done before you know it. Put a ground rod driver on it in aggregate soil, and you're done. Try driving it through serpantine bedrock like I occasionally must do, and you'll be spending another $600 soon, not to mention wasting a whole day, where a slide hammer or demo hammer would have done the jobe much faster. They also make huge bits that will fit these beasts. I have seen people use 2" bits and try to go throgh 2' of concrete, nearly breaking their arms when they hit the rebar, yet power through it, and take all day doing it. Me, I call a proffessional to do that job, and often will have core drilling NIC. This guy shows up mounts his diamond wet core drill, he's done in a half an hour. I pay him $250, to do what I foolishly would have attempted all day at low - mid jouneyman wage ($25 - $30 x 8) for a guy to risk getting hit in the face with a drill, go on Comp' and have a burned out tool, and a worn out bit. If the hole is crooked, the core saw guy will "staighten it" for free. ( I figure it's a bargain!) My guys on a rotor hammer are not cheap!
Anyway, that is my speal on hammer-drills. And, yes, I have thought about going into the core saw buisiness! Add that to GPR (Ground Penitrating Radar), and you have a money maker!
