nestork wrote:

'Pete C.[_3_ Wrote:
;3251331']
I take it you've never actually tried this. Do you even own a drill?

There is absolutely no need to start insulting me, Pete.

If you believe that there are tungsten carbide tipped drill bits that
CUT into masonry just like a twist drill bit cuts into wood, then can
you explain why a masonry drill bit doesn't have a sharp edge on it like
a twist drill bit does?

That is, how would this drill bit:

http://blumol.net/images/products/b_rtryhamr-db.jpg

be optimally designed to _CUT_ into masonry when there are not sharp
edges to it? Don't you agree that the only edge that can be argued to
be "sharp" might be the one facing directly forward, in which case it's
not designed to CUT masonary as it rotates.

On the other hand, it's easy to explain why the shape of that tip is
designed to bash the masonry in front of it into dust.

--
nestork

If you look at the front of that bit you can clearly see that the two
faces of the carbide tip are ground with relief angles giving the
cutting edge. It's not a fine edge like you will find on a twist drill,
but it is indeed a cutting edge. Look at some carbide milling / turning
inserts and you will also find profiles that are less visibly sharp than
you might expect. Carbide is hard but brittle and thin "sharp" edges
will fail quickly.

I have and have used multiple hammer drills and rotary hammers from
Makita, Hilti and others, and percussion rated masonry bits are indeed a
different species from regular hardware store rotary masonry bits. I've
also used carbide core bits which also are not intended for percussion
use (neither are the diamond ones).