The symptom pattern

The drill runs, the chuck turns, holes still get drilled in wood and steel — but in masonry it suddenly takes forever, because the hammer action has faded or vanished. Owners often describe a change in sound: the sharp knock of the impact mechanism is replaced by plain motor whirr. The HR2470 is one of the most common SDS+ drills in circulation, so this failure is thoroughly documented.

What’s actually happening

SDS rotary hammers don’t hit the bit with a spring — they use a pneumatic system. A motor-driven piston compresses an air cushion inside a cylinder, and that cushion flings a striker against the bit. The seal is maintained by rubber O-rings, and the whole assembly depends on the right grease.

Age and heat harden the O-rings and dry the grease. Once the air cushion leaks past the seals, the striker stops flying, and the hammer action fades — usually gradually, which is why owners often only notice when it’s nearly gone. It’s a wear item, not a design flaw: every pneumatic SDS drill gets here eventually.

Working through it

Before opening anything, eliminate the two-second explanations: a mode selector that hasn’t fully clicked into the hammer position, and a dry SDS shank — the bit must be lightly greased and free to slide a few millimetres in the chuck, because that float is how the impact reaches it.

If those check out, the diagnosis moves inside. With the drill unplugged, opening the gearbox exposes the piston and striker; their O-rings should be plump, flexible, and snug in their grooves. Flattened, cracked, or hardened rings — or grease that’s turned to black paste — confirm the diagnosis.

The fix

Replace the O-rings (sold individually or in cheap service kits, matched by the parts diagram) and repack the mechanism with SDS-hammer-rated grease — not general-purpose grease, which is too thick for the pneumatic action. Reassemble, then run the drill against scrap masonry for a minute to redistribute the grease; the hammer knock should return immediately and strengthen as it beds in.

Verdict

Cheap and satisfying. Parts cost is minor, the mechanism is honestly serviceable, and the drill comes back with full impact energy. On a machine as common and capable as the HR2470, this repair is always worth doing.