I have read the FAQ for drills and drill bits but neither have answered
my question.  

I am shopping around for a drill, one that will drill through wood then
brick to a total depth of 16mm: to re-affix a wooden gate post to a
brick wall.  I am very new to DIY and whilst I understand the need for
different drill bits.  I don't understand the difference between drill
types.  I gather that performance is one feature, and I assume the
order is impact < hammer < percussion.  What is the essential
difference between an impact drill, hammer drill and a percussion drill
- apart from price?  I deduce that the difference is due to the internal
construction.  I have asked at the various diy stores (B&Q, Homebase,
Wicks) but the staff have not been able to give me a satisfactory
answer, apart from this one is better than that one but not answering
why this so.

your thoughts would be welcome

akm


-- 
akmirza