Impact Driver
A driver that adds a rotational hammer blow to the turning motion, so it drives and removes screws that would stall an ordinary drill. Fast, and completely blind to how tight the joint ended up.
What it does
- Driving long wood screws without a pilot hole
- Removing seized or damaged screws
- Batch assembly, where speed matters more than a torque figure
Materialswhat it is used on
All materialsFasteners it fits21 standards specify hexagon socket / slotted
All standardsMatched on the drive form recorded against each standard, not on the tool's own claims — so this list changes when the fastener data changes, not when this paragraph does.
What to look forthe judgement calls, before the spec sheet
- The bit holder is a hex shank, not a chuck. Anything you intend to drive has to come as a hex-shank bit — round-shank drills do not fit.
- Impact drivers take standard 1/4-inch hex accessories; impact wrenches take square anvils. The two are not interchangeable, and the names are used loosely in shops.
- Choose the driving mode deliberately. Most have a slow self-tapping mode that disables the hammer, which is what you want for a screw you cannot afford to strip.
Misuse and safetythe ways this tool causes rework
- It cannot meet a specified torque. The hammer engages when resistance rises, so the same trigger pull produces different torque in different joints. Specified figures belong to a torque wrench.
- Do not use one to loosen a fastener you intend to reuse if the thread is fine or the material is soft — the shock load rounds heads, and an impact over-tightens a screw into a tapped hole until the thread fails.
Frequently asked questions
Impact driver or drill for screws?
A drill for a few screws and for anything with a torque figure; an impact driver for volume and for long screws in dense stock. An impact driver does not need a pilot hole where a drill would, and that is exactly why it is the wrong tool when the hole was dimensioned.
Can an impact driver replace an impact wrench for bolts?
No. The hex shank limits it to 1/4-inch accessories, and the torque is a fraction of a wrench's. For hex head bolts and nuts, use a socket on an impact wrench or a wrench.
Why are impact driver bits sold in bulk?
Because the hammer blow is hard on them. Bit life is the real running cost of the tool, and the torsion-zone bits that absorb the shock last longer than rigid ones in the same application.