"Peter Fairbrother" wrote in message
...
snip----

I don't know how they work, because they don't look too different, but I
am
convinced - apart from centers, I'll never use a centre drill to start a
hole again.

The one big difference is rake angle. Center drills are zero rake, do not
cut to center, and have little chip relief. Those conditions do not lend
themselves to easy machining.

Harold