Get the Best Cordless Drill
Although cordless drills and impact drivers have been a mainstay of carpentry work and remodleing for more than 20 years, brushless versions are only starting to gain traction in the marketplace. Brushless drills and impact drivers cost $100 more than a comparable tool with a brushed motor, so are these tools worth thier additional cost? Before answering that question, let’s talk a little about how brushless motors are different from conventional brushed motors.
A conventional brushed motor has four main parts: carbon brushes, a ring of magnets, an armature, and a commutator. During operation, DC current travels from the battery, through the brushes, and into the commutator, which passes the charge on to the armature’s copper windings. The windings are magnetized by the current, causing them to push against the stationary magnets that surround the windings, which makes the motor turn. When you release the trigger, the current stops, and the drill stops turning.
A brushless motor eliminates the brushes and commutator and places the magnets on the motor shaft, instead of surrounding it. Instead of rotating, the copper windings are fixed and surround the magnets on the motor shaft. The current from the battery is delivered through a circuit board to the windings. The circuit board only deliveres the power necessary to do the job which saves battery power. Brushless motors are also more powerful, because the windings can be larger, and there’s no drag on the motor from the brushes.
One other advantage of brushless motors is they’re shorter than a brushed motor, resulting in a tool with a smaller housing that can better fit in tight spaces. That all sounds good, right? But as I mentioned earlier, brushless motors cost more than traditional motors. I’m told by tool-industry insiders that brushless motor are especially valuable on impact drivers and cordless hammer drills, because the brushes have to be held especially tight to the commutator on these tools, in particular, because of the tools’ impacting action. As a result, the drag on the motor sacrifices battery life more than it would with tools that don’t experience so much vibration.
So if you want maximum run-time and power, and you’re willing to shell out an extra $50 to $100, you’ll want a cordless drill with a brushless motor. Bosch, DeWalt, Hitachi, Makita, Metabo, Milwaukee, Panasonic, and Festool all offer cordless drills and impact drivers with brushless motors.
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Conventional brushed motors have a pair of carbon brushes that provide electrical power to the commutator. The commutator rapidly switches the polarity of the electromagnets which turns the motor shaft.
In a brushless motor, computer circuitry replaces carbon brushes. Without brushes constantly dragging on the commutator, brushless motors have more power, longer run-times, and they're shorter, so the motor housing is smaller.