Drilling machine

Content
• Introduction
• Classification of Drills
• Types of Drilling Machine
• Drilling Machine Operations
• Twist Drill Terminology
• Reaming, Tool Holding Devices, Cutting Speed, Feed
and Depth of Cut

Introduction
• The drilling machine is a very important machine tool in the industry
• Drilling is an operation through which holes are produced in a solid metal by
using a revolving tool which is called Drill.
• In a drilling machine holes are drilled quickly and at a low cost.
• Therefore, for accurate holes, drilling is followed by another operation which
is called as Reaming.
• In reaming operations, a multi-tooth revolving tool is used which is termed
as reamer.
• Sometimes, for enlarging an existing hole size, one more operation is done
which is know as boring.

Working Principle Of Drilling Machine:
• In a drilling machine, the work piece is clamped
firmly on the worktable by using nuts and bolts.
• The tool used to produce holes in solid material
called as drill is press fitted in a drill chuck.
• The rotating drill is made of harder material than
that of the w/p by hand feed as well as power feed.
• During the operation, the material is removed in the
form of chip.
• It is important to note that, during the process high
amount of heat is generated, hence continuous
supply of coolant is required.

Classification of Drills
1) According to the type of shank
a) Parallel shank b) Taper shank
2) According to the type of flutes:
a) Flat drills b) Twist Drills
3) According to length of drill
a) Short Series drills b) Stub Series Drill c) Long series drills
4) According to the applications:
a) Core drills b) Centre drills c) Masonary drills
5) According to the material of tool
a) High speed steel drills b) Carbide tipped drills

Types of Drilling Machines
a) Portable drilling Machine
b) Sensitive drilling Machine
1)Bench Mounting Machine 2) Floor Mounting Machine
c) Upright drilling Machine
1) Round column machine 2) Box column machine
d) Radial drilling machine
1)Plain machine 2) Universal machine 3) Semi-universal machine
e) Deep hole drilling machine
1) Vertical machine 2)Horizontal machine
f) Gang Drilling Machine
g) Multiple spindle drilling machine
h) Automatic drilling machine

Portable Drilling Machine
• Portable drilling machine is very small, compact
and self contained unit carrying a small electric
motor
• It is generally used for drilling holes in
components which cannot be transported to the
workshop, because of their size of weight
• In such cases, the drilling operation is performed
on the site by using portable electric drill.
• Portable drills are light in weight and
manufactured in different size and capacities.
• Usually, they are made to hold drills of sizes
12mm to 18mm diameter

Portable Drilling Machine
• One of the major advantages of portable drills is
that, the holes can br drillled at any desired
inclination.
• As small size of drill is used, the machine is
operated at high speed
• The motor used in machine is universal type
which may be driven by AC or DC supply
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Sensitive Drilling Machine
 This is a light weight, high
speed machine designed for
drilling small holes in light
jobs.
 The machine has only a hand
feed mechanism for feeding
the tool into the workpiece.
 This enables the operator to
feel how the drill is cutting
and accordingly he can control
the down feed pressure.
 The basic components are as
follow:

Base:
The base is a heavy casting that supports the machine structure.
It provides rigid mounting for the column and also stability to the machine.
The base is usually provided with holes and slots which help to bolt the base
to a table or bench and allow the work-holding device or the work piece to
be mounted on the base.
Column:
The column is a vertical post that holds the worktable and the head
containing the driving mechanism.
The column may be of round or box section.

Table:
The table may be rectangular or round.
It supports the work piece and is carried by the vertical column.
The surface of the table is 90-degree to the column axis and it can be raised,
lowered and swiveled around it and
It can be held at any position by various levers provided.
Slots are provided in most of the tables to allow the jigs, fixtures or large work
pieces to be securely fixed directly to the table.

Drilling Head:
The drilling head is mounted close to the top of the column and houses the
driving arrangement and variable speed pulleys.
This unit transmits rotary motion at different speeds to the drill spindle.
The hand feed lever is used to control the vertical movement of the spindle
sleeve and the cutting tool.
The system is called the sensitive drilling machine as the operator is able to
sense the progress of drill with hand.

Upright Drilling Machine
• Upright drilling machine is similar to sensitive drilling machine for having a vertical
column mounted on the base.
• But, this machine is larger and heavier than sensitive drilling machine and is supplied with
power feed arrangement.
• This machine is suitable for handling medium sized work pieces.
• In this machine, a large number of spindle speeds and feeds are available for drilling
different types of work piece and the table of the machine has different type of adjustments.
• There are two classes of upright drilling machine
1) Round column section or pillar drilling machine
2) Box column section drilling machine

Pillar Drilling Machine
1. Base
2. Column
3. Table
4. Head
5. Spindle and drill head assembly
6. Spindle drive and feed mechanism
1. Base
 It is part of m/c on which vertical column is mounted.
 In belt drive machine the countershaft consists of a fast
and loose pulley and cone
pulley is fitted to the base of the m/c.
 .

 The top of the base in round column type upright
drilling m/c is accurately machined and has T-slots on it
so that large w/p and work holding devices may be set
up and bolted to it.
2. Column
 It is the vertical member of the m/c which
supports the table and the head containing all
the driving mechanism.
 It should be sufficiently rigid to take up the entire
cutting pressure of the drill.
 It may be made of box section or round section.
 Box column is more rigid.

3. Table
 It is mounted on column and is provided with T
slots for clamping the work directly on its face.
 It may be round or rectangular in shape.
 For centering work below the spindle, the table of a
pillar drilling machine may have three types of
adjustment: vertical adjustment
: radial adjustment about column
: circular adjustment about its own axis.

4. Head
 It is mounted on the top of the column and houses
the driving mechanism for the spindle.
 In some m/c the drill head may be adjusted up or
down for accommodating different heights of
work in addition to the table adjustment.
 In lighter m/c , the driving motor is mounted at the
rear end of the head
counterbalancing the weight of the drill spindle.

5. Spindle and Drill head assembly
 The spindle is vertical shaft which holds the drill.
 It receives its motion from the top shaft through bevel gears.
 A long key way is cut on the spindle and bevel gears is connected
to it by sliding key.
This construction is made allow the spindle to be
connected with the top shaft irrespective of its position
when the spindle is raised or lowered for feeding the drill
into the work.
 The spindle is rotates within a non rotating sleeve (quill).

6. Spindle Drive mechanism
 The spindle drive mechanism of a drilling machine incorporates an arrangement
for obtaining multiple speed of the spindle similar to the lathe to suit various
machining conditions.
It may be obtained as follows:
1. By step cone pulley drive
2. By step cone pulley drive with one or more back gears
3. By gearing

Difference Between Round and
Box Section column Drilling
Machine
Sr.No Round column drilling machine Box column drilling machine
1 It consists of a round column It consists of a box column
2 The column is fitted on the floor of the
machine
The column is fitted on the slides at the front face of
machine column
3 It has low strength and rigidity compared to
box column drilling machine
It has high strength and rigidity compared to round
column drilling machine
4 It is difficult to work with heavy work piece
on round column machine
It can work with heavy workpieces
5 The table can rotate in an arc upto 180
degree
The table is not allowed to rotate, it can only slides up
and down
6 Maximum upto 50mm diameter hole can
be drilled
Holes more than 50mm in diameter cn be drilled

Radial Drilling Machine
• A radial drilling machine is used to perform the
drilling operations on the workpieces which are
too heavy and also may be too large to mount
them on the worktable of the vertical spindle
drilling machine.
• It consists of a heavy base and a vertical column
with a long horizontal/radial arm extending from
it and can be rapidly raised, lowered and swing in
horizontal plane about the main column to any
desired location. The drilling head can move to
and fro along the arm and can be swiveled only
in the universal radial drilling machines, to drill
holes at an angle.

Radial Drilling Machine
• The combinations of motions of the radial arm and
drilling head offer a great deal of flexibility in
moving the drill to any position.
• The main advantage of the radial drilling machine is
that the drilling can be carried out on heavy
workpieces in any position without moving them.
• This type of drilling machine is used in tool rooms
and in large scale die manufacturing units

Gang Drilling Machine
• When several drilling spindles are mounted on a single
table, it is known as a gang drill.
• In this type of drill, each of these spindles can be
independently set for different speed and depth of cut.
• Such machines are useful when number of holes of
different sizes are to be drilled on the same workpiece.
• Apart-from drilling, a number of other machining
operations like reaming, counter boring, tapping etc. can
also be performed at a time on this machine.

Gang v/s Multispindle
Drilling Machine
Sr
no
Multiple spindle drilling machine Gang drilling machine
1 Two or more spindles are driven from a
common driving shaft by a single motor
Series of single spindle drilling heads driven by separate
2 Number of holes are produced
simultaneously as all the spindles are
fed at the same time
Number of drilling operations are performed in certain
squence, hence the component moves from one drilling
head to the next
3 All spindles are fed at the same time Speeds and feeds of the spindle are controlled
independently
4 The drill heads has fixed tools Each drill head is equipped with different tools
5 Feeding motion is obtained by raising
the table and elimating the movement
of heavy geared dril head
Feed is normally given by lowering the drill head

Gang v/s Multispindle
Drilling Machine
Sr
no
Multiple spindle drilling machine Gang drilling machine
6 As the number of spindles are more drill
jigs can be used
Generally drill jigs are not used

Turret Drilling Machine
• A turret machine overcomes the floor space restriction
caused by a gang drill press. A six-turret NC drill press.
• The stations are set up with a variety of tools.
Numerical control is also available.
• Two fixtures can be located side by side on the
worktable, thus permitting loading and unloading of
one part while the other part is being machined ; this
reduces the machine cycle.

Deep Hole Drilling Machine
• These machines are used for drilling holes whose depth
exceed normal drill size. These machines are operated at high
speed and low feed.
• These machines are either horizontal or vertical. The work or
the drill may revolve. Most machines are of horizontal
construction using a center-cut gun drill, which has a single
cutting edge with a straight flute running throughout its
length.
• Oil under high pressure is forced to the cutting edge through
a lengthwise hole in the drill. In gun drilling the feed must be
light to avoid deflecting the drill and causing it to meander
through it length.
• These machines are very useful for drilling deep holes in rifle
travels, crankshafts etc.

Multi Spindle Drilling Machine
• These machines are vertical type machines.
They permit drilling of several holes of
different diameters simultaneously
• Generally the spindles numbering 2 or 3 or
even more are driven by only one gear in the
head through universal joint linkages. Each
spindle is mounted with a twist drill. A jig is
used to guide the twist drill.
• These machines are mostly used in
continuous production shops where several
holes of same diameter or different
diameters are to be drilled simultaneously
and accurately.

Drilling Machine Operations
The different 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
8. Trepanning

1. Drilling :
• Drilling is the operation of producing circular hole in a
Solid metal by using revolving tool which is called drill.
• Before drilling, the center of the hole is located on the
workpiece by drawing two lines at right angle to each
other and center punch is used to produce an indentation
at the center.

2. Reaming:
Reaming is the operation of finishing an existing hole very smoothly and accurately in size.
A drill will not produce a hole having sufficiently good
qualities of finish and accuracy for many purposes.
Therefore, when a very accurate, smooth hole is required
the hole is first drilled a little undersize. Then it is reamed
to the correct size.
Reaming for finishing to size a drilled hole.
The accuracy to be expected is within ± 0.005 mm

2. Reaming:
A reamer is a multi-tooth cutter which rotates and moves
linearly into an already existing hole.
The previous operation could be drilling or preferably
boring. Reaming provides a smooth surface as well as
close tolerance on the diameter of the hole. Generally the
reamer follows the already existing hole and the,
therefore, will not be able to correct the hole
misalignment.

3. Boring
• Boring is the process of enlarging a drilled hole by
Using an adjustable cutting tool which is called
as boring tool
• The boring operation is used for the following
Purposes:
 To finish a drilled hole accurately and
bring it to required size.
 to correct the roundness of a hole

4. Counter-boring
• The operation which is used for enlarging only limited
portion of the hole is called as counter boring and the tool
used for this purpose is called counter bore.
• Counterboring operation in which the enlarged hole forms
a square shoulder with the original hole.
• The cutting edges of counterbore may have straight or
spiral teeth

5. Counter- sinking
• Counter sinking operation is used for enlarging the end of a hole and to give it a contain
shape for a short distance.
• Counter sinking operation in which the tool used is called as countersunk
• The standard countersinks have the included angle of 60, 82 or 90
degree and cutting edges of tool are at the conical surface.

6. Spot facing
It is the operation of smoothing and squaring the surface around a hole for seat of a nut
or the head of a screw
The hole may be spot faced below the rough surface or above it
For spot facing counterbore or special spot facing tool is used.

7. Tapping
• Tapping is an operation of cutting internal threads by using a
cutting tool called as tap
• For tapping purpose, the machine should be equipped with a
reversible motor or some other reversing mechanism
• A tap is considered as a bolt with accurate threads cut on it
and the threads act as cutting edges which are hardened and ground
• Tapping operation in which the tap is screwed into the hole
and metal is removed

8. Trepanning
 It is the operation of producing a hole by removing the
metal along the circumference of a hollow cutting tool.
 This operation is performed for producing large holes &
grooves around.

Twist Drill Terminology
Twist drill is most widely used tool in drilling, which consists of a cylindrical body carrying
two spiral flutes on it.
Twist drills are generally made of high speed steel (HSS).
Twist drill consists of two main parts i.e. shank which is gripped in the drill chuck or sleeve
and the body which forms the main cutting unit.
Terminology is are as below:

1. Body: Body is that part of the drill which carries flutes and extends from the dead
centre upto almost the start of the neck.
2. Axis: It is the longitudinal centre line of the drill, along which the whole body, neck and
shank of the drill are concentric to each other .
3. Chisel edge or dead centre: Due to the intersection of the flanks, a short edge is formed at
the extreme tip of the drill
4. Shank: The portion of the drill beyond the neck, which is gripped in the holding device
such as drill chuck.
5. Point: The cone shaped surface at the end of flutes, formed by grinding and containing the
Dead centre, lips and flanks

6. Lip or cutting edge: Lip is the main cutting part of the drill and is formed by intersection of
each flank and face.
7. Body clearance: It is a small reduction in the diameter of the body which is provided on the
drill adjacent to the land.
8. Land: Is the narrow flat surface which runs all along the flutes of the drill on its leading edges
9. Face: It is the curved surface near the lip.
10. Flutes: The helical grooves provided in the drill body
11. Neck: It is the smaller diameter cylindrical portion which separates the body and the drill
shank
12. Tang: The flat portion of rectangular cross-section provided at the end of the tapered shank
13. Heel: It is an edgge formed due to intersection of the body clearance and flute of the drill

14. Length of body: The length measured along the axis between the dead centre and start of
the neck of a drill.
15.Flute length: It is the length measured parallel to the axis between the dead centre and the
point of termination of the flute near the neck.
16.Overall length: It is the distance measured along the axis between the dead centre and the
Point of the termination of the flute near the neck
17. Lead of helix: It is axial distance measured between two corresponding points on a flute in
Its one complete turn.

Reaming
• Practically it is not possible to produce a hole of the exact size through drilling.
• Hence, to achieve or to produce an exactly round and smooth hole of correct size, the hole
is drilled and then reamed.
• It is operation of finishing a hole to bring it to accurate size and have a fine surface finish.
• Reaming operation is performed by using a multitooth cutter called as reamer
Types Of Reamers:
1) Hand Reamers 2) Chucking or Machine reamers 3) Adjustable reamers 4) Expansion
reamers 5) Taper reamers 6) Taper pin reamers 7) Shell reamers 8) Carbide tipped reamers

Reaming
Hand Reamers
Generally, hand reamers are provided with a parallel shank and square tang.
The flutes of hand reamer may be straight or spiral
In order to have an unrestricted entry into the previously drilled hole, the reamer carries a
Taper towards the end of its flutes.
In any case, these reamers are not used for machine reaming.

Reaming
Adjustable Reamers
These type of reamers are available in both straight and tapper shank.
The main body of these reamers consists of parallel grooves in which adjustable blades are
Fitted
These blades are flexible (in and out ), so that the same reamer can be easily adjusted to suit
different sizes of hole.
Another advantage of these reamers is that, its blades can be easily sharpened and adjusted,
hence they have longer life
The main limitation of these reamers is, its high initial cost.

Tool Holding Devices
Drill Chucks
• Most common devices used for holding straight-shank
cutting tools.
• Most contain three jaws that move
simultaneously when outer sleeve turned
• Hold straight shank of cuttingtool securely.
Two common types
• Keyed and Keyless
• Keyed
Three jaws move simultaneously when outer sleeve
turned
• Tighten with key
• Different size keys for different size chucks.

Keyless
Chuck loosened or tightened by hand without key
Holds smaller drills accurately.
Drill Sleeves and socket
Drill Sleeves
Used to adapt drill shank to machine spindle if taper on
tool is smaller than taper in spindle.
Drill Socket
Used when hole in spindle of drill press too small for taper
shank of drill.
Used often as extension sockets.

Drill Drift
• Used to remove tapered-shank drills or
accessories from drill press spindle.
• Always place rounded edge up so this
edge will bear against round slot in
spindle.
• Use hammer to tap drill drift and loosen
tapered drill shank.
• Use board or piece of pressed-wood to
protect table or vise.

Alignment Tests on Drilling
Machine
• All machine tools used for production need to be tested at the time of their first
installation and periodically during use to ensure that they have the capability to
produce the accuracy and finish expected from them and continue to have such
capability even after use.
• So geometrical characteristics and various movements test are carried out for
machine tools.
• Perpendicularity of drill head guide with table.
This test is carried out with help of block square (frame level) as shown in fig, 3.20 in
two planes.
a) In a vertical plane passing through the axes of both the spindle and column
b) A plane at right angle to the above plane.

Machine
A block square or frame level with graduations from 0.03 mm 0.05 mm/meter is
placed on the guide column and the table and level reading are noted. Permissible
error. For (a) 0.25 mm/1000 mm with column inclined at upper end towards the front.
- For (b) 0.15 mm/1000 mm.

Machine
True running of spindle taper.
• This test is carried out with taper test mandrel
attached to tapered bored spindle. As shown in fig.
3.21 dial indicator is kept on the table and plunger is
in touch of the mandrel.
• Rotate the spindle slowly and note the dial reading
• Permissible error 0.03 mm/100 mm for machine
having taper up to morse taper No.2.

Machine
Parallelism of spindle axis with its vertical movement.
• In this test mandrel is attached to spindle as shown
in Fig. 3.22.
• Keeping plunger in touch with mandrel, spindle is
moved up and down with slow vertical feed motion.
This test is performed in two mutually
perpendicular planes A and B. and note the dial
reading
• Permissible error for both plane A and B is 0.03
mm/100 mm.

Machine
Squareness of spindle axis with table.
In this test dial is set as shown in fig. 3.23. Table is kept in middle of its travel and plunger of
dial is ke] at position P on straight edge PQ on the table. Take the reading for position P. Then
rotate the spindle throug 180° so that dial gauge is now at position Q and again take the
reading
The difference between these two reading is the error in squareness of the spindle axis with
table Shift the straight edge to position RS and again take the readings Permissible error :
0.08 mm/300 mm for position PQ 0.05 mm/300 mm for position RS.

Drilling machine

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