Homework: Impact drivers
A drill-hammer
Impact drivers have been around for years, and if you look at the name of the tool, it should solicit some interest -- as in "impact." Hand-powered impact drivers are still available today and work by combining the downward force provided by a hammer blow with the simultaneous twisting motion of the tool. These combined forces can really tighten a screw or bolt or loosen stubborn ones. The only downward force a powered impact driver gets is if you push down on the tool as it's being used. That force is nowhere near as powerful as that given by a hammer strike.
Labor-saving
All that aside, the powered cordless impact drivers are time and money savers. They also save your wrist, hand and fingers from repetitive motions that can lead to physical injury or from fatigue that can contribute to injury.
This is not a drill
The powered impact drivers differ greatly from the standard power drill. If you've ever driven a four-wheel drive vehicle that has three different transfer case settings, or even a regular standard transmission that has a very low first gear, you can start to appreciate how an impact driver differs from a regular drill.
Packs a punch
A powered impact driver has different internal gears that deliver much greater torque to the tip of the tool as it turns than a standard power drill. Imagine putting a four-wheel drive vehicle in 4W-drive low and giving the vehicle gas. This gearing allows the power from the engine to be concentrated to move a heavy load slowly or go up a steep hill with virtually no effort. A powered impact driver employs this same mechanical advantage. It needs to concentrate the power of the motor on the head of the fastener and deliver power, not speed. A drill is geared just the opposite. Drills tend to spin much faster, meaning they don't have great power at low revolutions a minute.
It has stamina
A powered impact driver will drive hundreds and hundreds of decking screws and not complain. You can use it very effectively when screwing cabinets to a wall. It works to remove uncompromising and uncooperative screws and bolts.
-- Tribune Media Services
