DRILLING OPERATION

2. 2
DRILLING MACHINE

3. 3
DRILLING
Drilling is a metal cutting process carried
out by a rotating cutting tool (twist drill)
to make circular holes in solid materials.

4. 4
A power operated machine tool, which holds the
drill in its rotating spindle and produces a hole when
moved linearly against the work piece.
Drilling Machine

5. 5
Twist Drill

6. 6
Types of Drilling Machines
Drilling machines may be classified as
Bench or Sensitive drilling machine.
Radial drilling machine.

7. 7
BENCH DRILLING MACHINE

8. 8
Bench Drilling Machine

9. 9

10. 10
• Located generally on the work bench
• Used for small jobs, also called as sensitive drilling machine.
• Used for drilling small and medium sized holes (up to 15mm ).
• Consists of a round column with a rigid base fastened to the bench
• Has a work holding table and an arm mounted on the round column
• Arm carries the drill spindle on one side and the drive motor on the
other side
• A stepped cone pulley with V – belt is used to transmit the power
from motor to spindle
Bench Drilling Machine

11. 11
• The work table can be moved up and down to suit the
required job height and can be locked at suitable height
• The table can rotate about its axis by 360°
• Drilling operation is performed by fixing the job properly on
the work table
• Drill bit is gradually fed by rotating hand feed lever towards
the work piece
• Once the required depth of cut is completed, the feed lever is
rotated in the opposite direction to withdraw the tool from
the work.
Bench Drilling Machine

12. 12
Radial Drilling Machine

13. 13
• Radial drilling machine is used for medium and heavy
duty applications
• Consists of a heavy, circular column mounted on a very
strong base
• Radial arm that can swing around is mounted on the
column and the radial arm can be raised and lowered
• Drill head with drive and feed mechanism is fitted on
to the radial arm
• Drill head can move horizontally along the guides of
the arm and can be locked at any desired position
Radial Drilling Machine

14. 14

15. 15
Types of Drilling Machines
Drilling machines may be classified as
1. Portable drilling machine.
2. Bench or Sensitive drilling machine.
3. Radial drilling machine.
4. Pillar drilling machine.
5. Gang drilling machine.
6. Multiple spindle drilling machine.

16. 16
List the operation performed on a drilling machine.
The different machining operations that can be performed
on a drilling machine are as follows.
1. Drilling
2. Reaming
3. Boring.
4. Counter Boring
5. Counter sinking
6. Spot facing
7. Tapping.

17. 17
Boring:
• Done on a drilling machine to
increase the size of an
already drilled hole
When a suitable size drill is not
available,
■ Initially a hole is drilled to
the nearest size
■ Using a single point cutting
tool, the size of the hole is
increased to required size
By lowering the tool while it is continuously
rotating,
■The size of the hole is
increased to its entire depth.

18. 18
Counter boring
It is to increase the size of a
hole at one end only through
a small depth
It forms a larger sized recess or
a shoulder to the exiting hole
• The cutting tool will have a
small cylindrical projection
known as pilot
• It guides the tool
Counter bore
Tool
Pilot

19. 19
Condition:
• Diameter of the pilot will
always be equal to the
diameter of the
previously drilled hole
Cutting Speed:
• Two-third of the drilling
speed
Counter bore
Tool
Pilot
Purpose:
It is done on the hole to accommodate the socket head screw, or grooved nuts, or
round head bolts.
Counter boring

20. 20
Countersinking
It is the operation of making
the end of the hole into a
conical shape
• Using countersinking tool
• May also be employed for
deburring the holes
Cutting speed
One - half of that used for
similar size drill
Use:
When the countersunk screws
are to be screwed into the holes,
so that their top faces have to be
in flush with the top surface of the
work piece.

21. 21
Drilling Operations

22. MILLING MACHINES
22

23. Milling Machine
• Milling is a metal cutting operation in which the operating tool is a
slow revolving cutter having cutting teeth formed on its periphery.
• The milling cutter is a multipoint cutting tool. The work piece is
mounted on a movable work table which will be fed against the
revolving milling cutter to perform the cutting operation.
23

24. • The difference between drilling and milling is that, in
drilling a rotating drill is fed against a stationary
work-piece, while in milling the work-piece is fed
against a milling cutter which only revolves.
• Similarly, it also differs from the lathe operation
because the lathe tool is fed against rotating work-
piece.
• A milling machine is a power operated machine tool in
which the work-piece mounted on moving table is
machined to various shapes when moved under a
slow revolving serrated cutter.
24

25. Principle of Milling
• The Figure 1 shows the principle of cutting action of the milling cutter.
The milling cutter is mounted on a rotating shaft known as arbor. The
work-piece which is mounted on the table can be fed either in the
direction opposite to that of the rotating cutter as shown in Fig.1A or
in the same direction of that of the cutter as shown in Fig.1B.
25

26. • When the work-piece is
fed in the opposite
direction to the cutter
tooth at the point of
contact, the process is
called conventional or up
milling.
• In this process, as the
work-piece advances
against the rotating
cutter, the chip that is
removed gets
progressively thicker as
shown in Fig.1A
26

27. • The action of the cutter forces the work-piece and the
table against the direction of the table feed, thus each
cutter tooth enters a clean metal gradually thus the
shock load on each tooth is minimized.
• The disadvantage of this method is that when making
deep cuts, such as in heavy slotting operations, the
cutter tends to pull the work-piece out of the vice or
the fixture since the cutting force is directed upward
at an angle.
27

28. • When the work-piece is
fed in the same
direction as that of the
cutter tooth at the
point of contact, as
shown in Fig. 1B, the
process is called climb
or down milling.
• In this process, the
cutter enters the top of
the work-piece and
removes the chip that
gets progressively
thinner as the cutter
tooth rotates.
28

29. • Generally, more metal can be removed for each cut
than the conventional up milling. Climb milling is used
only on materials that are free of scale and other
surface imperfections that would damage the cutters.
• Classification of Milling Machine
• Plain or Horizontal Type of Milling Machine
• Vertical Milling Machine
• Universal Milling Machine
• Planer Type Milling Machine
• Profile Cutting Milling Machine
29

30. 30

31. 31

32. 32

33. 33

34. SHAPER
• The shaper is a reciprocating type of machine tool
intended primarily to produce flat surfaces.
• These surfaces may be horizontal, vertical, or inclined.
• In general shaper can produce any surface composed of
straight line elements.
34

35. STANDARD SHAPER
35

36. • Ram: it holds and imparts cutting motion to the tool
through reciprocation
• Bed: it holds and imparts feed motions to the job
• Housing with base: the basic structure and also
accommodate the drive mechanisms
• Power drive with speed and feed change mechanisms.
• Shaping machines are generally used for producing flat
surfaces, grooving, splitting etc.
• Because of poor productivity and process
capability these machine tools are not widely used
now-a-days for production.
36

37. Grinding Machines
37

38. • Grinding, also called abrasive machining, is a process
in which the material is removed in the form of fine
chips, almost as dust particles by the abrasive action
using some kind of abrasive materials.
• The thickness of the material chips removed by
grinding ranges from 0.25 to 0.50 mm in finishing and
general grinding operations.
• Abrasive is the mineral material employed for
sharpening, grinding and polishing operations
38

39. • The two types of abrasives used are; natural and
artificial.
• The examples of natural abrasives are emery,
corundum, quartz. sandstone, diamond, etc.
• The important properties of abrasives are, hardness,
toughness, uniformity in grain sizes, and sharpness.
39

40. Grinding wheel Terminology
• Grit
• The grit is the grain size of the abrasive grain.
• The grain size is expressed as a number. Thus, coarse grain size can
be between 10 and 24, Medium grain size can be between 30 & 60,
Fine grain size can be between so and, very fine grain size can be
between 220 and 600.
40

41. • Grade
• Grade is the hardness of the bond, which is
designated by alphabets. The letter "A" Stands for
very soft material and the letter " Z" stands for very
hard grade.
• Wheel structure
• The abrasive grains are distributed over the abrasive
wheel in a structural form. The wheel structure is also
represented as a number. For example, Dense can be
from 1 to 8 and Open can be from 9 to 15.
41

42. • Bond type
• It is denoted by alphabets like V is for vitrified Bond, B
is for Resinoid, R is for Rubber, E is for shellac and S is
for silicate, and so on.
• Abrasive
• Abrasives are denoted by alphabets-Example: A
stands for Aluminum oxide & C Stands for Silicon
Carbide.
42

43. 43

44. 44

45. 45

46. 46

47. 47