Impact driver vs impact wrench: hex bits or square drive?

The shared mechanism

Inside both tools a spring loaded hammer spins with the motor. When the fastener resists, the hammer disengages, rotates, and strikes an anvil, delivering a sharp rotational blow. Many such blows per minute keep the fastener turning without the steady reaction that would twist your wrist.

The difference is size and what the anvil holds. The driver's anvil ends in a hex collet for bits. The wrench's anvil is a square drive that takes impact sockets, and the hammer mass and motor are scaled up for far higher output.

Hex holder against square anvil

A 1/4 inch (6.35 mm) hex quick release holder takes screwdriver bits, nut drivers, hex shank drill bits and small socket adaptors. It is quick to change and suits repetitive screw driving.

Impact wrenches come with square drives, most often 1/2 inch for automotive and general use, 3/8 inch for compact models, and 3/4 or 1 inch for heavy plant. A friction ring or detent pin holds the socket. You use impact rated sockets, which are thicker and tougher than chrome hand tool sockets.

Which jobs suit which tool

An impact driver is the tool for decking, framing, fencing, roofing screws, cabinet installation and small coach bolts into timber. Its compact head reaches between joists and its hex collet makes bit changes quick.

An impact wrench is the tool for wheel nuts, seized exhaust and suspension bolts, scaffolding and agricultural fasteners, and anything where you would otherwise reach for a breaker bar. Mid torque 1/2 inch models suit most car work. High torque models are built for large seized nuts.

• Building a deck or a stud wall: impact driver.
• Swapping winter wheels or removing a seized bolt: impact wrench.
• Large coach bolts into oak beams: either, but a wrench with a socket is faster on big hex heads.

Can one do the other's job?

With a hex to square adaptor an impact driver can turn small sockets, which is handy for light nuts. It does not make the driver an impact wrench: output is far lower, and the adaptor can snap on stubborn fasteners. See can an impact driver remove wheel nuts.

Fitting a bit holder to an impact wrench is possible but clumsy, and the high output will snap screws and strip heads. For screws, stay with a driver. Our impact driver guide compares drivers with clear box contents.

Note:Use impact rated bits and sockets only, and never chrome hand tool sockets on an impact tool, as they can shatter. For wheel nuts, always finish with a calibrated torque wrench to the vehicle maker's figure. Wear eye protection and follow the tool manual.

Choosing on your battery platform

Most brands sell both tools on the same battery. If you already own an 18 V drill and driver, adding a bare impact wrench later is straightforward. Check whether the listing is a bare unit and whether it is a compact, mid torque or high torque model, and match the anvil size to sockets you own.

If you are choosing a first platform, read how to choose a cordless battery platform and compare twin packs.

Frequently asked questions

Is an impact wrench the same as a torque wrench? No. An impact wrench spins fasteners quickly and has limited control over final torque. A torque wrench is a hand tool used to tighten to an exact figure.

Can I use an impact driver for lug nuts? Small adaptors make it possible on light nuts, but output is often too low for wheel nuts that are tight or corroded, and over tightening is a risk. A mid torque impact wrench is the right tool.

Why do some listings call impact drivers wrenches? Translation and naming vary. Check the output: a 1/4 inch hex holder means it is a driver, a square drive means it is a wrench.

Do I need special sockets? Yes. Use impact rated sockets, usually black, which are designed for the hammer blows.