On Sun, 23 Nov 2008 01:37:25 -0800 (PST), tonyjeffs wrote:

I've just knackered a £12 sds drill bit after one session, cutting a
big hole in a wall for a wc waste,

Sounds like you are using a bad technique or you where drilling something
*very* hard. You don't need to push hard on an SDS drill like you do with
an ordinary hammer drill. Push enough to stop the bit from chattering
round or in the chuck but there is no need to lean on it. The cutting come
from the heft impacts that the SDS mechanism delivers.

Usually, I dip a bit in cold water occasionally in such circumstances,
but i got lazy and was impressed the way that SDS bits are slow to get
hot.

I wouldn't do that to any drill, heaven knows what the thermal shock will
do to the tempering...
Many of the sds bits have a sort of nipple on the end, almost a bell
or bobble hat shape - is that important ?

Mine don't, at least not that I have noticed. They all seem broadly like
the ends of two cold chisels joined at an angle.

Can I maybe buy a bit sharpening machine?

Martek, if it's still about, for small HSS and ordinary masonary drill
with the correct stone.

--
Cheers
Dave.