useful for all engineering students who are studying mechanical

1. Drilling machine
By
Polayya ( Asst Prof, Mech Dept)
Lendi Institute of Engineering &Tech

2. Introduction
 Drilling is a metal cutting process carried
out by a rotating cutting tool to make
circular holes in solid materials.
 Tool which makes hole is called as drill bit
or twist drill.

3. Drilling machine
 A power operated machine tool which holds
the drill in its spindle rotating at high
speeds and when actuated move linearly
against the work piece produces a hole.

4. Types of drilling machine.
 Portable drilling machine
 Bench drilling machine
 Radial drilling machine
 Upright Drilling machine
 Gang drilling machine
 Multiple drilling machine

5. Portable drilling machine

6. Bench drilling machine
 These are light duty
machines used in small
workshops.
 Also called Sensitive drilling
machines because of its
accurate and well balanced
spindle.
 Holes of diameter 1 mm to
15 mm.

7. Bench drilling machine

8. parts
 Vertical main column
 Base
 Moving drill head
 Work table
 Electric motor
 Variable speed gear
box and spindle feed
mechanism.

9. working
 Work piece with the exact location marked
on it with the centre punch is clamped
rigidly on the work table.
 spindle axis and center punch indentation
are in same line.
 Machine is started and drill bit is lowered
by rotating feed handle.
 Drill bit touches the work and starts
removing material.

10. Radial drilling machine
 These are heavy duty
and versatile drilling
machine used to
perform drilling operate
on large and heavy
work piece.
 Holes up to 7.5 cm.

11. parts
 Heavy base
 Vertical column
 Horizontal arm
 Drilling head

12. working
 Work piece is marked for exact location
and mounted on the work table.
 Drill bit is then located by moving the radial
arm and drill to the marked location.
 By starting drill spindle motor holes are
drilled.

13. Up-Right Drilling Machine
 Drill
holes
upto
50mm
 Table
can
move
vertically
and
radially

14. 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

15. Drill Materials
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

16. Tool Nomenclature

17. Drilling machine operations
 Reaming
 Boring
 Counter boring
 Counter sinking
 Spot facing
 Tapping

18. Reaming
 It is a process of smoothing the surface of
drilled holes with a tool.
 Tool is called as reamer.
 Initially a hole is drilled slightly smaller in
size.
 Drill is replaced by reamer.
 Speed is reduced to half that of the drilling.

19. Reaming

20. Boring
 It is process carried on a
drilling machine to
increase the size of an
already drilled hole.
 Initially a hole is drilled
to the nearest size and
using a boring tool the
size of the hole is
increased.

21. Counter boring
 This process involves
increasing the size of a
hole at only one end.
 Cutting tool will have a
small cylindrical
portion called pilot.
 Cutting speed = two-
thirds of the drilling
speed for the same hole.

22. Counter sinking
 This is an operation of
making the end of a
hole into a conical
shape.
 Cutting speed = half of
the cutting speed of
drilling for same hole.

24. Spot facing
 It is a finishing
operation to produce
flat round surface
usually around a drilled
hole, for proper seating
of bolt head or nut.
 It is done using a
special spot facing tool.

27. Tapping
 Process of cutting
internal threads with a
thread tool called as
tap.
 Tap is a fluted threaded
tool used for cutting
internal thread
 Cutting speed is very
slow.

29. Types of cutters
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.

30. 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.

31.  Step Blocks
 Clamps
 V-Blocks
 Angles
 Jigs
 T- Slots Bolt
Work Holding Devices

32. Definitions
 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

33. 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

34. 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 rusting

35. Safety Precautions
 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.