What is an impact driver used for?

How an impact driver works

The motor turns a spindle that carries a spring loaded hammer. While the screw turns easily, the hammer and anvil turn together like a normal driver. When the screw resists, the hammer slides back against its spring, rotates, and snaps forward to strike the anvil. This happens many times a second, giving the bit a series of sharp rotational blows.

Those blows are tangential, around the axis of the bit, not forward like a hammer drill. Because the force comes in short bursts, very little reaction twist reaches your wrist.

The hex bit holder

Impact drivers use a 1/4 inch (6.35 mm) hex quick release collet. Pull the collar, push the bit in, release. Some models, such as the DeWalt DCF870, have a drop and load holder for one handed changes. The collet holds screwdriver bits, nut drivers, hex shank drill bits and socket adaptors.

Use impact rated bits, which have a torsion zone that flexes slightly to absorb the blows. See impact driver bits explained.

Jobs an impact driver does best

Impact drivers excel where screws are long, numerous or large.

• Decking screws into joists, hundreds at a time.
• Long timber screws for framing, sheds and stud walls.
• Coach screws and small coach bolts into posts and beams.
• Self drilling screws into steel framing and roofing.
• Cladding and fencing screws.
• Nuts and small bolts using a nut driver or socket adaptor.

Where a drill is still better

A drill has a clutch that stops at a set torque, which is better for small screws, hinges and soft materials. It has a chuck that takes round bits and hole saws, and a hammer mode for masonry. For drilling holes, especially accurate or large ones, a drill is the right tool.

That is why most people own both. Read combi drill vs impact driver.

Torque, speed and control

Impact drivers list high torque figures, often around 150 to 230 Nm on 18 V models. The Milwaukee M18 FID2 lists 226 Nm and the Bosch GDR 18V-215 lists 215 Nm. That power can snap small screws or bury heads, so many drivers have speed modes or special modes for self tapping screws.

Quieter designs use hydraulic or oil pulse mechanisms. The HiKOKI WHP18DA and DeWalt DCF870 are examples; they trade some torque for lower noise and smoother control.

Compare impact drivers →

Choosing one

Pick a driver on the battery platform you already use, or as part of a twin pack. Look at torque, speed modes, head length and whether the listing includes batteries. Our impact driver guide and twin pack guide state what is in each box.

Note:Impact drivers are loud. Wear hearing protection for long sessions, plus eye protection, and keep your supporting hand away from the bit and screw. Follow the manual and HSE guidance on noise.

Tips for better results

Start screws at low speed until they bite, then increase. Keep the driver in line with the screw and push firmly so the bit stays seated. Stop as soon as the head is flush; impacts keep driving and can sink heads below the surface or snap thin screws. In hardwood, drill a pilot hole first.

If your driver has modes, use the lowest for small screws and the highest only for long screws and bolts. Some Bosch models have Auto Driving Modes that slow or stop automatically.

Is it the same as an impact wrench?

No. An impact wrench uses the same principle but has a square drive for sockets and much higher torque, for nuts and wheel bolts. See impact driver vs impact wrench.

Frequently asked questions

Can I use an impact driver for drilling? Yes, in wood and thin metal with hex shank bits. It is not suitable for masonry and is less accurate than a drill for large holes.

Why is my impact driver so loud? The hammer striking the anvil is noisy. Hydraulic or oil pulse drivers are quieter. Wear hearing protection.

Do I need an impact driver for flat-pack? No. A drill with a clutch, or a hand screwdriver, is better for flat-pack, where over tightening damages chipboard.

Can an impact driver remove stuck screws? Often yes, because the blows help break the screw free. Use a good fitting impact bit to avoid stripping the head.