There is some good info at the address below. Personally I use a 1/2" 2 speed Ryobi that will work as a hammer or two-speed drill. The drill has served me well at least 30 years for light work and heavy work. Versatile in weight and uses means a lot to me vs having excess tools with little use (or tool's weight killing me). I thought the 2 speed gears would be better than variable for toughness. Toughness and torque is what you need for deep drilling in concrete or steel vs a variable mode. I like a 3/8" with variable and clutch modes for medium duty work. My opinions from years of various handyman work. The job and your time should dictate the tools. loger

http://en.wikipedia.org/wiki/Hammer_drill

Oops Bosch vs Byobi! I have a older ýâ Bosch Hornet 2 speed hammer & rotary w/o reverse and etc as todayâÂÂs drills. The support handle is a must for your safety while using the strong drill.

Milwaukee, Bosch, Makita and other industrial brands are good tools also. If it will be for industrial use only, the industrial connection is the way to go. Speed Is Money! loger

I have a Bosch, Black and Decker, and a Skill, all do what they were designed to do, but the ones I have are too light to make a living with. If I had to do heavy duty I would buy an industrial tool like Milwaukee, Hilti, or any other heavy duty tool. Of the three I have the Bosch is my favorite, but I have never drilled anything over 1/2" dia.x 3" deep. If I want to drill small holes in brick I had rather use the Skill because it weighs much less.

Larry