Cordless impact drivers transformed site fixing the moment they became standard kit, but they have also been the single biggest cause of broken screwdriver bits in the last fifteen years. The reason is simple: a regular drill puts a smooth torque on a screw, while an impact driver puts a hammering torque that spikes and releases dozens of times a second. Standard screwdriver bits aren't built for that kind of cyclic load and snap, often at the bit tip.
Impact-rated bits are made from a different steel grade with a controlled torsion zone behind the tip. Under impact load, the bit twists slightly in the torsion zone rather than fracturing at the tip. They look almost identical to ordinary bits from the outside, but the difference shows the first time you drive a 100mm screw into hardwood. Look for the word “impact” on the packaging and a gold-coloured or black torsion zone behind the head.
Tip styles matter too. Pozi (PZ) and Phillips (PH) are not interchangeable, despite looking similar; using the wrong tip cams out under load and wrecks the screw head and the bit together. Torx (T-series) is the go-to for decking screws, structural fixings and most modern timber screws because it doesn't cam out under high torque. Square (Robertson) shows up on imported and joinery hardware. The full bit range sits under drill and screwdriver bits.
Bit holders are a smaller part of the story but a real one. A magnetic bit holder with a worn or weak magnet drops bits constantly; a sliding bit-lock holder is a much better investment for site work. If your impact driver itself is dropping bits, the 1/4” hex collet has lost its ball-spring tension and the collet needs replacing.
For the impact driver itself, the wear parts are the usual ones — brushes for older brushed models, switches and the anvil bearing for high-mileage cordless tools. The DeWalt brush range covers the older corded impact drivers, and replacement bearings are the standard sealed types specified by dimensions on the seal.