Every cordless impact driver has a gearbox, which transfers power from the motor to the chuck in the form of torque and speed. Torque is the turning force of the cordless impact drivers chuck, while the speed is how fast the chuck turns. Depending on the make and model of the cordless impact driver, the gearbox may offer the possibility to select different gears.
Simply put, gears dictate the amount of speed and torque being delivered to the chuck. Different amounts of speed and torque are needed for different screwdriving or drilling tasks. A tool with multiple gears will allow you to vary the power according to the task at hand.
Cordless drills and screwdrivers
In the case of cordless drill drivers and screwdrivers, torque and speed have an inverse relationship (when one increases, the other decreases.) For these tools, low gears produce low speeds and high torque, and high gears produce high speeds but low torque.
Cordless impact drivers
Because cordless impact drivers are more powerful, torque and speed are balanced, so the tool is able to produce both high torque and high speed, simultaneously. This means that low gears produce low speeds and low torque and high gears produce high speeds and high torque.
As a result, most cordless impact drivers can complete a variety of screwdriving applications in less time than cordless drills and screwdrivers. Some cordless impact drivers only have 1 gear and some models have 2 or 3.
Why are gears important?
Basically, gears break up the tool’s power into manageable chunks, preventing too much torque and speed from being delivered at one time.
For example, a light-duty application involving small thin screws requires less power. Using too high a gear for this sort of task means you wouldn’t have to pull the speed control trigger in very far to release a lot of speed and torque. If you needed a lot to get going, that wouldn’t be a problem, but for light duty applications it’s easy to over-squeeze the trigger, release too much power and sink the screw beneath the surface of the material or damage its head.
If used correctly, gears give you more control when working and stop the tool delivering more power than is needed.