On 17/02/2021 15:35, Jimmy Stewart ... wrote:
Just got my first keyless chuck drill and I am having
problems......bought a new bosch 550 wired drill to replace my old black
and decker and Stanley drills and a 20mm masonry drill to open up the
holes in a teracotta airbrick.....anyway got the bit tightened and
started drilling on the hammer settings and after a few seconds the
drill fell out and rolled down the roof to the ground......this can't be
normal... am I doing something wrong?....instructions just say tighten
until clicks are heard......doesn't matter how tight I make it the drill
still falls out....any ideas ? ...


It may be defective or it may be operator error:

If the chuck touches anything whilst rotating, it can open it. Make sure
it doesn't.

You may not be tightening it enough.