On Fri, 04 Sep 2009 23:43:15 +0100, John Rumm
wrote:

Sounds like the end got snagged on a stone or something - or perhaps it
lost its carbide edge on one side and hence started drilling unevenly.

That's exactly what happened. A brand new, never used, drill bit went
into the wall, and when it came out the carbide edge was only present
on one side. It was a Bosch bit too, so I had expected better.

I remember trying to drill small holes in a concrete floor so that I
could screw carpet grips into yellow plugs. I used Bosch bit for that
and it melted! Perhaps I was too heavy handed that time too? But my
experience with this limited number of Bosch bits has not been
positive; perhaps they are just rebadged? I've used the cheapest
Toolstation bits without problems. YMMV etc.