Tool Feature: Cordless Impact Drivers
Pluses and minuses
Impact drivers bring a lot of pluses to your shop, along with a few minuses.
• 3 to 4 times greater torque than a drill of equal voltage, yet lighter and smaller.
• Requires less arm strength for tough drilling and driving tasks.
• Fewer stripped screwheads.
• Great for assembling machines and tool stands, and unsticking stubborn screws and bolts.
• Short, powerful turns in impact mode make fastener-depth control easier.
• Drilling with small-diameter bits (less than 3/4") works like with a cordless drill because the impact function doesn't kick in unless the wood proves tough.
• Perfect for drilling with large-diameter bits because impact function prevents binding that's common to drills.
• Impact hammering creates loud noise, so have hearing protection handy.
• High speeds with 18-volt models--prior to impact mode kicking in--make for a steep learning curve.
• They only work with 1/4" hex-shank bits--a detriment for small-diameter drilling (less than 1/2") because these bits tend to be of lesser quality.
• Difficult to gauge screw depth when working in "blind" situations, such as poorly lit areas inside cabinets or inside pocket holes.
• High torque can twist off screws if pilot holes are too tight or you drive screws too deep. It can also damage ordinary drilling and driving accessories, as shown above right, so look for those made specifically for impact drivers.