8
Quick Facts About Drill Bits
118° STANDARD POINT: This drill bit point angle is considered a
standard general purpose geometry . It is used for drilling soft or
mild materials such as cold rolled steel, aluminum, and wood.
Typically the standard drill bit is made of High Speed Steel (HSS).
The tip of the drill bit can easily be split making it a High
Performance drill bit.
135° HIGH PERFORMANCE SPLIT-POINT: The flatter point
angle of this drill is designed for harder, tougher materials such as
tempered steels, hard alloys or hard cast metals. Metal types in
split-point drill bits vary (see below). Due to the thicker web and
flat point angle this drill point works best when its split-point is
maintained.
MASONRY DRILLBITS: This point angle is typically 130° to 135°.
New masonry drill bits are generally sharpened with a facet or flat
style grind. Masonry drilling is typically not a precision operation.
The masonry drill bits resharpened with the Drill Doctor® will
look different due to a radial (curved) grind. However, this style of
grind will perform as well as the original drill point.
SPLIT POINTS: Split point drill bits tend not to walk around on the
material before they begin to cut. This feature is described as self
centering. The need to center punch is effectively eliminated. A
standard drill bit chisel point has to wear an area in the middle of
the hole prior to the cutting lips removing material. Due to its
additional cutting lips along the chisel edge a split point will begin
cutting immediately. Up to 70% less thrust (when compared to a
non-split or conventional point) is required to drill a hole with a
split point. You can split either the 118° or the 135° degree points
with Drill Doctor®.
CARBIDE DRILL BITS: This point angle is typically 130º to 135º.
Carbide is harder and more brittle than high speed steel and cobalt.
This type of drill is used for drilling tempered steels, alloys, glass,
Etc. Carbide drill bits can be sharpened with your Drill Doctor®.
PARABOLIC AND COBALT DRILL BITS: Have a thicker web
than regular drill bits. Parabolic drill bits are designed to drill deep
holes. Cobalt drill bits are Titanium Nitride (TiN) coated. TiN is
applied to increase a drill bit’s cutting efficiency. Most of these
drill bits can be sharpened with your Drill Doctor®.
LIP RELIEF ANGLE: The relief on a drill bit is the downward angle
between the cutting lips (leading edge) and the heel (trailing edge)
on the drill point. If the drill bit cutting lips are not higher than the
heel, then the drill bit will not cut into the material. This is often
referred to as negative relief (see page 5 &10). The Drill Doctor®
is designed to grind a standard factory relief on your drill bits.
CHISEL EDGE ANGLE: The chisel edge is the line across the point
of a drill bit. Note in Figure 27 the chisel edge angle is between
120
º
and 135
º
. Another way to look at a chisel edge is to imagine
the drill point as a clock face with the chisel angle pointing to an
approximate one o’clock position. Most drill bits are set to this
angle.
WEB: The web is the core thickness of a drill point. It is typically
around 10% of the drill bit diameter. As a drill bit is sharpened the
web thickness will increase. Splitting the point or thinning the web
on a drill bit will maintain drill bit performance (See Figure 26).
ANATOMY OF A DRILL BIT
120° to 135°
Chisel Edge
Angle
Masonry
135°
118°
Fig. 25
Fig. 26
Fig. 27
Included Angle
of Point 118°
QUICK FACTS
Cutting Lip
Chisel Edge
Heel
(25 pages)
(26 pages)
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