In article ,
Christian McArdle wrote:
The hammer action works by literally hammering the end of the bit, which
is very effective because the sliding action means that the chuck can
remain firmly attached to the motor whilst the bit flies forwards and
backwards. A traditional "hammer" drill can't do this because the bit is
firmly attached to the chuck, so it just wobbles it a bit from side to
side, which is totally pants in comparison.

On my normal hammer drill, the whole chuck assembly goes in and out.

I reckon SDS works better in 3 ways:-

The lower mass of the drill against a drill/chuck combination makes the
impact greater even if the 'hammer' were the same.

The impact mechanism is better - a hammer drill uses a ramp mechanism,
and there's a limit to the acceleration that can be achieved. IIRC, SDS
uses a pneumatic system.

The SDS bit can't slip even slightly in a rotary direction.

Feel free to add or subtract. ;-)

--
*Before they invented drawing boards, what did they go back to?

Dave Plowman London SW 12
RIP Acorn