The document discusses drilling operations and drilling machines. It describes how drilling is used to create circular holes using a rotating cutter called a drill. It outlines different types of drilling machines like portable, sensitive, radial, and upright drilling machines. It also discusses different types of drills, drilling operations, workholding devices used in drilling, and basic safety procedures for operating drilling machines.

2.  Drilling is the operation of producing circular hole in the
work-piece by using a rotating cutter called DRILL.
 The machine used for drilling is called drilling machine.
 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.
 The most common drill used is the twist drill.

3.  It is the simplest and accurate machine used in
production shop.
 The work piece is held stationary, that is
clamped in position and the drill rotates to make
a hole.
 Types :-
a) Based on construction:
Portable, Sensitive, Radial, up-right, Gang,
Multi-spindle
b)Based on Feed:
Hand and Power driven

4.  Drill holes from
1.5 mm to 15 mm
 Operator senses
the cutting action
and hence called
sensitive drilling
machine

5.  Drill holes up to
50 mm
 Table can move
vertically and
radially.

6.  It the largest
and most
versatile
machine used
for drilling
medium to large
and heavy work
pieces.

8. The two most common types are
1. HSS drill
- Low cost
2. Carbide- tipped drills
-high production and in CNC
machines
Other types are
Solid Carbide drill, TiN coated drills, carbide
coated masonry drills, parabolic drills, split point
drill

9. Drilling And Drills
Types of drills
– Twist drill: most
common drill
– Step drill:
produces holes
of two or more
different
diameters
– Core drill: used
to make an
existing hole
bigger

10. Drilling operations
Drilling Centre Hole
Drilling Deep Holes
Drilling Thin Material
Drilling Pilot Hole

13.  Body clearance: That portion of the body surface which is
reduced in diameter to provide diametral clearance.
 Chisel edge: The edge formed by the intersection of the
flanks. This edge acts as a flat drill and cuts its own hole in
the work piece.
A great amount of axial thrust is required to cut a hole by the
chisel edge. In some drills chisel edge is made spiral
instead of a straight one. This reduces the axial thrust and
improves the hole location.
 Face: The portion of the flute surface adjacent to the lip on
which the chip impinges as it is cut from the work.
 Flutes: The groove in the body of the drill which provides the
lip.
 Heel: The edge formed by the intersection of the flute surface
and the body clearance.
 Land: The cylindrically ground surface on the leading edges
of the drill flutes. The width of the lands is measured at right
angles to the flute helix.

14.  Lip (cutting edge): The edge formed by the intersections of
the flank and face. Both the lips should be at the same angle
of inclination with the drill axis, usually 59 degrees for
general work. Both the lips should be of equal length.
 Point: the sharpened end of the drill consisting of all the parts
of the drill which is shaped to produce lips, faces,, flanks and
chisel edge.
 Right hand cutting drill: A drill which cuts when rotating in
counter-clockwise direction viewed on the point end of the
drill.
 Tang: The flattened end of the taper shank intended to fit
into the drift slot in the spindle, socket or drill holder.
 Angles
 Chisel edge angle: The obtuse angle included between the
chisel edge and the lip as viewed from the end of the drill.
(120 – 135 degrees).
 Helix angle: Angle formed by the leading edge of the land
with a plane having the axis of the drill. Value of rake angle is
30 degrees.

15.  Point angle: Angle included between the two lips projected
upon a plane parallel to the drill axis and parallel to the two
cutting lips.The usual point angle is 118 degrees.

16.  The different methods used for holding drill in a
drill spindle are
 By directly fitting in the spindle hole.
 By using drill sleeve
 By using drill socket
 By using drill chuck

18.  Operations that can be performed in a drilling
machine are:
 Drilling
 Reaming
 Boring
 Counter boring
 Countersinking
 Tapping

21. Reamers :-
Multi tooth cutting tool
Accurate way of sizing and finishing the pre-existing hole.
Accuracy of 0.005mm can be achieved
Boring Tool:-
Single point cutting tool.
Boring tool is held in the boring bar which has the shank.
Accuracy of 0.005mm can be achieved.

22. Countersinks :-
Special angled cone shaped enlargement at the
end of the hole
Cutting edges at the end of conical surface.
Cone angles of 60°, 82°, 90°, 100°, 110°, 120°
Counter Bore Tool:-
Special cutters uses a pilot to guide the cutting
action .
Accommodates the heads of bolts.

24. Combined Countersinks and central drill :-
Special drilling tool to start the hole accurately.
At the end it makes countersinks in the work
piece.
Gun drill :-
Machining of lengthy holes with less feed rates.
To overcome the heating and short life of the
normal drill tool

25. Tapping:-
 For cutting internal thread
 Multi cutting edge tool.
 Tapping is performed either
by hand or by machine.
 Minor diameter of the
thread is drilled and then
tapping is done.

26.  1. Machine Table
Vice

27.  Step Blocks
 Clamps
 V-Blocks
 Angles
 Jigs
 T- Slots Bolt

28.  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
axis
d = D / 2

29. 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

30.  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 rusting

31.  Do not support the work piece by hand – use
work holding device.
 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 breaks inside the work
piece.