Too often when we are confronted with a different application or even trying to find
a better way for an existing one, most of us
tend to overlook the possibility of using a
drill with features other than a conventional
This is where the flat bottom drill can
make life and the application at hand
go much easier. When the application
demands some form of a flat bottom hole,
typically manufacturers have a drill ground
with flat cutting edges to produce this flat
configuration at the bottom of the hole.
Today some carbide tool manufacturers
are seeing a need for a range of standard
type drills with flat cutting edges as opposed
to 118 to 140° point angles. These flat
bottom drills are ideal for producing flat
bottom holes. They can also drill parts with
angular surfaces, radii, and cross holes with
interruptions, as well as aligning pre-drilled
holes, round parts, open existing holes,
produce a counter-bore, and a variety of
other unique applications.
Often ignored by many is the fact that
with the correct end face configuration on
the “flat” drill, it can drill easily to depths
exceeding 5 XD and still maintain hole
accuracy and positional integrity.
Few carbide tool manufacturers have
developed a dual configuration end face, or
one that comprises a cutting centre point to
maintain tool centrality, combined with flat
cutting edges to produce the desired flat
bottom. Such a tool variation covers the best
of both worlds.
With the development of expert CNC
grinding technology, multi-axis tool grinders
can be programmed to produce those dual
point configurations, which can then be
utilized as variable use drilling tools.
The dual configuration end face has
been produced on solid carbide tools and
has been well accepted in machining to
perform operations as previously noted, so
where could you expand the development
of these tools?
By using the dual face tool on a solid
carbide drill, the user would typically have
to regrind it using a CNC five axis grinder,
which most users don’t typically have in
their shops. If the dual face configuration
is on an insert, you then use the insert and
then discard it, so you don’t need to spend
the time or money to regrind it.
The next logical step would then be to
have greater versatility by manufacturing the
dual configuration end face on a carbide
insert, which can be indexed after use. This
would reduce the cost and also eliminate the
Fortunately there are companies who have
taken this next step to make the tool totally
versatile, not only manufacturing an insert
with dual end face at 180°, but also offering
other angles on request.
One such company is Yestool Ltd., a
drill manufacturer based in Korea, that
manufactures flat bottom configurations
on inserts. It also has another claim to
fame; an indexing drill up to 50 times
diameter in depth. SMT
Flat Bottom Drilling
with flat bottom
can lead to lower
BY MaC MaCKeNzIe
Drills with flat
can produce a
variety of holes,
Mac Mackenzie is CEO
of Epic Tool.
Flat bottom configurations on inserts, such as this one
from Yestool Ltd., eliminates regrinding costs.
50 | CUTTING TOOLS | Tech Tips