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Drilling is a
for producing round
holes in metallic and
The machine used
for drilling is called
drilling machine as
shown in figure.
Tool which makes hole is called as drill bit.
Drill bit are the tools used to cut away fine shavings
material of work piece in a rotational motion.
The most common drill used is the twist drill.
The drilling operation can also be accomplished in
lathe, in which the drill is held in tailstock and the
work is held by the chuck.
CUTTING CONDITIONS IN DRILLING
Cutting Speed (v):-
It’s the peripheral speed of the drill
v = *D*N where
D = dia. of the drill in m
N = Speed of rotation in rpm
Feed Rate (f):-
It’s the movement of drill along the axis (rpm)
Depth of Cut (d):-
The distance from the machined surface to the drill
d = D / 2
Material Removal Rate:-
It’s the volume of material removed by the drill per unit time
MRR = ( D2 / 4) * f * N mm3 / min
Machining Time (T) :-
It depends upon the length (l) of the hole to be drilled , to the
Speed (N) and feed (f) of the drill
t = L / f N min
TYPES OF DRILL MACHINE
1. Portable drill machine.
2. Cordless drilling machine.
3. Hand drill machine.
4. Bench drilling machine or upright sensitive drill
5. Radial drilling machine
6. Gang drilling machine
7. Multiple drilling machine
PORTABLE DRILL MACHINE
It is used in domestic work.
Its shape like a gun.
Holes of diameter is approx.3to12.7mm.
A cordless drill is an electric
drill which uses recharable
batries.These drills are
available with similar
features to an AC mains-
powered drill. They are
available in the hammer
drill configuration and most
have a clutch, which aids in
driving screws into various
substrates while not
Bench drilling machine
These are light duty machines used in small
Also called Sensitive drilling machines because of
its accurate and well balanced spindle. And bit is
feed by hand.
Holes of diameter 1 mm to 15 mm.
Its spindle Rpm is approximately 800 to 1000.
The adjustment of the rpm is used by the help of
Parts of drilling machine
Moving drill head
gear box and
Radial drilling machine
These are heavy duty and versatile drilling machine
used to perform drilling operate on large and heavy
Holes up to 7.5 cm.
The range of speed of spindle 50 to 2800 rpm.
Parts of radial drilling machine
GANG DRILLING MACHINE
The gang style drilling machine or gang drill
press has several work heads positioned over a
single table. This type of drill press is used when
successive operations are to be done. For
instance, the first head may be used to make
hole. The second head may be used to boring .
The third head may be used, along with a
tapping head, to tap the hole. The fourth head
may be used to reaming.
MULTIPLE SPINDLE DRILLING M/C
The multiple spindle drilling machine is commonly
referred to as a multi spindle drill press. This
special purpose drill press has many spindles
connected to one main work head . All of the
spindles are fed into the work piece at the same
time. This type of drilling machine is especially
useful when you have a large number of parts with
many holes located close together.
Also called center drilling, this operation drills a
starting hole to accurately establish its location for
subsequent drilling. The tool is called a center drill.
A reamer enters the work piece axially and enlarges
an existing hole to the diameter of the tool.
A reamer is a multi-point tool that has many flutes,
which may be straight or in a helix.
Reaming removes a minimal amount of material and
is often performed after drilling to obtain both a more
accurate diameter and a smoother internal finish.
A countersink tool enlarges the top portion of an
existing hole to a cone-shaped opening.
Countersinking is performed after drilling to provide
space for the head of a fastener, such as a screw, to
sit flush with the work piece surface.
Common included angles for a countersink include
60, 82, 90, 100, 118, and 120 degrees.
A counter bore tool enlarges the top portion of an
existing hole to the diameter of the tool.
Counter boring is often performed after drilling to
provide space for the head of a fastener, such as a
bolt, to sit flush with the work piece surface.
The counter boring tool has a pilot on the end to
guide it straight into the existing hole
SPOT FACING OPERATION
• Spot facing is similar to milling. It is used
to provide a flat machined
• surface on the workpart in a localized
• Spot facing is commonly done on
castings where irregular surfaces are
• Spot facing may be performed on a drill
press with a counter bore of suitable size
for the operation.
A proper size pilot must be used whenever this is
done on the drill press.
This operation is performed by a tap and is used to
provide internal screw threads on an existing hole.
The twist drill or drill bit is made from High Speed
Steel, tempered to give maximum hardness
throughout the parallel cutting portion
Different helix angles are available for drilling a
range of materials.
Fit in chuck
Fit direct into spindle
The shank is the end of a drill bit grasped by the
chuck of a drill. The cutting edges of the drill bit
contact the work piece, and are connected via the
shaft with the shank, which fits into the chuck or
Flute is a groove on drill bit start from the shank
to the end point
Tang is flat surface on the upper side of drill bit used
to release drill bit from the socket or sleeve
• Recess or neck
It is in between body and shank it is also called stamp
portion from industry where the drill bit made and also
mention drill bit size
The body consist of flute,margin,body clearance and
Point is cone shaped end of drill bit which lip
clearance heel and dead center
Web is most important part of drill bit it is the
thickness of drill bit b/w flute.
Drill Bit Features
The point of the drill is
ground to an angle of
each side is ground
back to give " relief " of
about 12 degrees to
each cutting edge as
Twist drills Helix types
Standard quick helixslow
The helix angle of the twist drill is established
Drills with a helix angle of 20° — known as
slow-helix drills — are available with a point
angle of 118° for cutting brass and bronze
and with a point angle of 90° for cutting plastics
Quick-helix drills, with a helix angle of 40° and
a point angle of 100°, are suitable for drilling the
softer materials such as aluminium alloys and
The standard helix angle is 30 degrees, which,
together with a point angle of 118°, is suitable for
drilling steel and cast iron.
Precautions for Drilling machine
Lubrication is important to remove heat and friction.
Machines should be cleaned after use
Chips should be removed using brush.
T-slots, grooves, spindles sleeves, belts, pulley
should be cleaned.
Machines should be lightly oiled to prevent from
Do not support the work piece by hand – use work
Use brush to clean the chip
No adjustments while the machine is operating
Ensure for the cutting tools running straight before
starting the operation.
Never place tools on the drilling table
Avoid loose clothing and protect the eyes.
Ease the feed if drill bit breaks inside the work piece.
Fundamental of modern manufacturing
material processes and system by mikell
Slides from different universties.
Work-shop practice MT-236 by