Unit 3A2 - Drillling and related operations

Machining & Machining Tools
Unit-3A2
General Purpose and Special Purpose
Machine Tools
1
Drilling and related Operations, Drilling
Machine & Accessories

DRILLING-WORKING PRINCIPLE
 Drilling is an operation of making a circular hole by removing a volume
of metal from the job by cutting tool called drill.
 A drill is a rotary end-cutting tool with one or more cutting lips and
usually one or more flutes for the passage of chips and the admission of
cutting fluid.
 A drilling machine is a machine tool designed for drilling holes in
metals. Besides drilling round holes, many other operations can also
be performed on the drilling machine such as counter- boring,
countersinking, honing, reaming, lapping, sanding etc.
2
Tool Work Motions and G & D in Drilling

BASIC PURPOSE OF USE OF DRILLING MACHINE
Drilling machines are generally or mainly used to originate
through or blind straight cylindrical holes in solid rigid bodies
and/or enlarge (coaxially) existing (pre-machined) holes:
– of different diameter
– of varying length depending upon the requirement and
the diameter of the drill
– In different materials excepting very hard or very soft
materials like rubber, polythene etc.
3

ELEMENTS OF A DRILLING MACHINE
4

ELEMENTS OF A DRILLING MACHINE
 The head containing electric motor, V-pulleys and V-belt which transmit rotary
motion to the drill spindle at a number of speeds.
 Spindle is made up of alloy steel. It rotates as well as moves up and down in a
sleeve. A pinion engages a rack fixed onto the sleeve to provide vertical up and
down motion of the spindle and hence the drill so that the same can be fed into the
workpiece or withdrawn from it while drilling. Spindle speed or the drill speed is
changed with the help of V-belt and V-step-pulleys. Larger drilling machines are
having gear boxes for the said purpose.
 Drill chuck is held at the end of the drill spindle and in turn it holds the drill bit.
 Adjustable work piece table is supported on the column of the drilling machine. It
can be moved both vertically and horizontally. Tables are generally having slots so
that the vise or the workpiece can be securely held on it.
 Base table is a heavy casting and it supports the drill press structure. The base
supports the column, which in turn, supports the table, head etc.
 Column is a vertical round or box section which rests on the base and supports the
head and the table. The round column may have rack teeth cut on it so that the
table can be raised or lowered depending upon the workpiece requirements.
5

CLASSIFICATION OF DRILLING MACHINES
(a) Portable drilling machine
(b) Sensitive drilling machine
Bench mounting
Floor mounting
(c) Pillar Type drilling machine
Round column section
Box column section
(d) Radial drilling machine
Plain
Semi universal
Universal
(e) Gang drilling machine
(f) Multiple spindle-drilling machines
(g) Deep hole drilling machine
Vertical
Horizontal
6

PORTABLE MANUAL HAND DRILLS
 A hand drill has a turning handle connected to a drive wheel, which
turns a pinion gear that rotates the drill bit.
 As the drive wheel of the hand drill is much larger than the pinion
gear, it increases the speed at which the drill bit is turned.
 This increased speed of the drill bit makes hand drills better suited
than a brace would be for drilling small holes in hard material such
as metal, which require a higher cutting speed.
7

PORTABLE POWERED HAND DRILLS
hand drill is a portable drilling device which is mostly held in hand and
used at the locations where holes have to be drilled. As the name
indicates it is portable, it is light in weight and smaller in size. This
machine is driven by individual motor and sometimes driven by
pneumatic power
8

TABLE TOP SMALL SENSITIVE DRILLING MACHINE OR
BENCH DRILLS
These small capacity (≤ 0.5 kW) upright (vertical) single spindle drilling
machines are mounted (bolted) on rigid table and manually operated using
usually small size (φ≤ 15 mm) drills. Operator senses the cutting action so
sensitive drilling machine 9

PILLAR DRILLING MACHINE
These drilling machines are quite similar to the table top drilling machines
but of little larger size and higher capacity (0.55 ~ 1.1 kW) and are grouted
on the floor (foundation). Drill holes upto 50 mm
10

PILLAR DRILLING MACHINE
11
Column drilling machine:
These box shaped column type drilling machines are much more
strong, rigid and powerful than the pillar drills. In column drills the
feed gear box enables automatic and power feed of the rotating
drill at different feed rates as desired.
CNC column drilling machine:
Versatile and flexibly automatic drilling machine having box-column
type rigid structure and the work table movements and spindle
rotation are programmed and accomplished by Computer Numerical
Control (CNC).

RADIAL DRILLING MACHINE
12
This usually large drilling machine possesses a radial arm which along with the
drilling head can swing horizontally around the column and move vertically up
and down. The radial, vertical and swing movement of the drilling head enables
locating the drill spindle at any point within a very large space required by large
and odd shaped jobs.

GANG DRILLING MACHINE
 a drill press having two to six
upright drills connected
together in an in-line
arrangement.
 Each spindle is powered and
operated independently, and they
share a common worktable, so
that a series of drilling and
related operations can be
accomplished in sequence
(e.g., centering, drilling, reaming,
tapping) simply by sliding the
workpart along the worktable from
one spindle to the next. 13

TURRET (TYPE) DRILLING MACHINE
 Turret drilling machines are
structurally rigid column type but are
more productive like gang drill by
having a pentagon or hexagon
turret.
 The turret bearing a number of drills
and similar tools is indexed and
moved up and down to perform
quickly the desired series of
operations progressively in a
sequence.
 These drilling machines are available
with varying degree of automation
both fixed and flexible type.
14

MULTISPINDLE DRILLING MACHINE
a large number of
drills work
simultaneously on a
blank through a jig
specially made for the
particular job.
The entire drilling
head works repeatedly
using the same jig for
batch or lot production 15

DEEP HOLE DRILLING MACHINE
 Very deep holes of L/D ratio 6 to even 30,
required for rifle barrels, long spindles, oil
holes in shafts, bearings, connecting rods
etc, are very difficult to make for slenderness
of the drills and difficulties in cutting fluid
application and chip removal.
 For such operations machines like deep hole
drilling machine such as gun drilling
machines with horizontal axis which are
provided with
 high spindle speed
 high rigidity
 tool guide
 Pressurized cutting oil for effective cooling,
chip removal and lubrication at the drill tip.
 Deep hole drilling machines are available
with both hard automation and CNC system.
16

SPECIFICATIONS OF DRILL MACHINE
1. Table diameter
2. Number of spindle speeds and feeds available
3. Maximum spindle travel
4. Morse taper number of the drill spindle
5. Power input
6. Net weight of the machine
7. Floor space required, etc.
17

VARIOUS OPERATIONS BY DRILL MACHINE
Drilling
 Basic operation of making a circular hole by
removing a volume of metal from the job by a
rotating cutting tool called drill.
 Before drilling, the hole is located by drawing
two lines at right angle and a center punch is
used to make an indentation for the drill point at
the center to help the drill in getting started.
18
Centering/Centre Drilling
 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

19
Reaming
 Operation of sizing and finishing a hole
already made by a drill by means of a multi
tooth tool called reamer .
 Reaming operation serves to make the hole
smooth, straight and accurate in diameter.
 Reamer possesses several cutting edges on
outer periphery and may be classified as solid
reamer and adjustable reamer.
Boring
 Enlarging a hole by means of adjustable
cutting tools with only one cutting edge is
accomplished. A boring tool is employed for
this purpose.

20
Counter-Sinking
The top of the drilled hole
is beveled to
accommodate the conical
seat of a flat head screw
and counter sunk rivets
Counter-Boring
It is an operation of enlarging the mouth
of a drilled hole to set bolt heads and
nuts below the surface so that they may
not project out from the surface level.

Lapping
This is the operation of sizing and finishing a hole by removing very small amounts
of material by means of an abrasive. The abrasive material is kept in contact with the
sides of a hole that is to be lapped, by the use of a lapping tool. The laps fit in the
hole and are moved up and down while it revolves.
21
Grinding
to finish a hardened hole grinding wheel
is made to revolve with the spindle and is
fed up and down. A suitable grinding
wheel may be selected for surface
grinding operation. Grinding can also be
done to correct out of roundness of the
hole. The accuracy in grinding operation
is quiet high about ± 0.0025 mm.
Tapping
It is the operation of cutting internal threads by using a tool
called a tap. A tap is similar to a bolt with accurate threads cut
on it. To perform the tapping operation, a tap is screwed into
the hole by hand or by machine.

22
Trepanning
It is the operation of producing a hole by removing metal along the
circumference of a hollow cutting tool. This operation is performed for
producing large holes. Fewer chips are removed and much of the
material is saved while the hole is produced. It produces a hole by
removing a disk-shaped piece (core), usually from flat plates.

23
Spot facing
• This is the operation of removing enough material to provide a flat
surface around a hole to accommodate the head of a bolt or a nut. A
spot-facing tool is very nearly similar to the counter-bore tool.

TYPES OF DRILLS
24
According to shank type drills are available as
Straight (Fit in chuck. Upto ½ inch in dia) & Taper (Fit
direct into spindle, Tang provided on end to prevent
drill from slipping)
According to operations various drills are available. Operations have been
discussed already.
According to work Material
various drills are masonry drills,
spade drills for wood etc.

TYPES OF DRILLS
25
According to tool material they are Carbon-tool steels drills, High-speed
steel drills, Cemented-carbide drills
Various other drills available are step drills, core drills, spade drills , gun
drills etc

TYPES OF TWIST DRILLS
26
General Purpose Drill
 Have two Helical flutes
 Designed to perform well on wide variety of materials, equipment and job
conditions.
 Comes in varying point angle, speeds and feeds to be suitable for many conditions.
Low Helix Drill
 Developed primarily to drill brass and thin materials
 Used to drill shallow holes in some aluminum and magnesium alloys
 Can remove large volume of chips formed by high rates of penetration
High Helix drills
 Designed for drilling deep holes in
 aluminum, copper, die-cast material, and other metals
 – Material where chips have tendency to jam
 High helix angle (35º to 45º)
 Wider flutes assist in clearing chips from hole

TYPES OF TWIST DRILLS
27
Core Drill
 Three or four flutes
 Used to enlarge cored, drilled, or punched holes
 Produced in sizes from ¼ to 3 in.
Oil Hole Drills
 Have one or two oil holes running from shank to cutting point
 – Compressed air, oil, or cutting fluid can be forced through when deep holes being
drilled
 Cutting fluid cools drill's cutting edges and flushes chips out of hole
Straight Fluted drills
 Recommended for drilling operations on soft materials such as brass, bronze,
copper and various types of plastic
 Straight flute prevents drill from drawing itself into material while cutting and have
less of a tendency to "dig in" or grab the material.

ELEMENTS OF A TWIST DRILL
28
• Twist drill is a rotating cutting tool, used for cutting holes in rigid
materials, that consists of an essentially conical point, relieved
and fluted to form cutting lips, and spiral flutes which direct the
chips away from the lips and toward ejection from the hole.

29
 Axis: An imaginary longitudinal center line
 Body: The portion of the drill extending from the shank or neck to
the outer corners of the cutting lips.
 Shank: The part of the drill by which it is held and driven in
chucks.
 Tang: The flattened end of a taper shank, intended to fit into a
driving slot in a socket.
 Tang Drive: Two opposite parallel driving flats on the extreme
end of a straight shank.
 Flank: surface of drill, which extends behind the lip to the flute.
 Heel: The edge formed by the intersection of the flute surface and
the body clearance.
 Face: The portion of the flute surface adjacent to the lip, on which
the chip impinges as it is cut from the work.

30
• Overall Length: The length from the extreme end of the shank
to the outer corners of the cutting lips. It does not include the
conical shank end often used on straight shank drills, nor does it
include the conical cutting point used on both straight and taper
shank drills.
• Margin: The cylindrical portion of the land which is not cut away
to provide clearance between drill and work material
• Neck: The portion of reduced diameter in between the body and
shank
• Point: The cutting end of a drill, made up of the ends of the
lands and the web. In form it resembles a cone, but departs from
a true cone to furnish clearance behind the cutting lips.

31
• Back Taper: A slight decrease in diameter from point to back in
the body of the drill. It provides clearance between the drill and
workpiece preventing friction and heat.
• Drill Diameter - The diameter over the margins of the drill
measured at the point.
• Flutes: Helical or straight grooves cut or formed in the body of
the drill to provide cutting lips, to permit removal of chips and
make them curl, and to allow cutting fluid to reach the cutting lips.
• Flute Length: The length from the outer corners of the cutting
lips to the extreme back end of the flutes. It determines the
maximum length of drilling.
• Land - The part of the drill body between adjacent flutes.
Provides torsional strength. Reducing the land width increases
chip space , but reduces strength.

32
 Land Width - The distance in a transverse plane between the
leading edge and the heel of the land measured at a right angle
to the leading edge.
 Lips - The cutting edges of a two flute drill extending from the
chisel edge to the periphery. It is the cutting edge formed at the
intersection of flank and flute. (CORE DRILLS) - The cutting
edges extending from the bottom of the chamfer to the periphery.
 Web -The central portion of the body that joins the lands. The
extreme end of the web forms the chisel edge on a two-flute drill.
 Web Thickness - The thickness of the web at the point unless
another specific location is indicated. It contributes to torsional
strength.

33
 Body Diameter Clearance - That portion of the land that has
been cut away so it will not rub against the walls of the hole.
 Chisel Edge or dead Centre - The edge at the end of the web
that connects the cutting lips. It is the point where two cutting
edge meets at the extreme tip.
 Clearance Diameter - The diameter over the cut away portion of
the drill lands

ANGLES OF A TWIST DRILL
35
Chisel edge angle: The obtuse angle included between the chisel edge and the lip
as viewed from the end of the drill. It usually ranges from 120° to 135°. It is the angle
included between the chisel edge and lip of the twist drill when measuring on a plane
normal to the axis.
Helix angle or rake angle: Angle formed between a line drawn parallel to the axis of
the drill and the edge of the land. The value of rake angle varies between 18° to 45°;
its typical value is 30°. The rake angle governs the tightness with which chip curls
and hence the amount of space occupied by the chip. The higher rake angle cause
tightly rolled chip while the small rake angle tends to chip curl into more loosely rolled
helix. Large rake angle causes excessive vibration and chatter of drill.
Point angle: This is the angle included between the two lips projected upon a plane
parallel to the drill axis and parallel to the two cutting lips. Simply it is the angle
between the lips in the side view of a twist drill. The usual point angle is 118°.
Lip clearance angle – The angle formed by the flank and a plane at right angles to
the drill axis. The angle is normally measured at the periphery of the drill. Lip
clearance is the relief given to the cutting edges that allow drill to enter into the
workpiece without any hindrance. The lip clearance angle ranges from 12° to 15°.

Tool Holding Devices
36
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

Tool Holding Devices
37
With key:
 Small straight shank
type solid HSS and
carbide drill are held
in a drill chuck which
is fitted in the drill
spindle at its taper
bore.
 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
 Precision
keyless
 Holds smaller
drills accurately

Mounting of Jobs in Drilling machines
1. By directly clamp on table when job is heavy and/or of
odd shape and size
2. Using V Block
3. In a vice which is clamped on the bed
4. T-Bolts & Clamps
5. In a suitable jig clamped on bed
6. Step Blocks

39
Table
 Mounted on the column or
base
 Provided with T-slots for
clamping the work directly on its
face.
 May be round or rectangular in
shape.
V-block.
 Used for holding round work
pieces.
 Supported on two or three
blocks and clamped against
them by straps and bolts.
 Accurately machined cast iron
or steel blocks.

40
Drill Press Vice
 Used to hold round, square or odd-shaped rectangular pieces
 The work is clamped between a fixed jaw and movable jaw. Extra slip jaws
are supplied for holding cylindrical or hexagonal bars.
 The screw of the vice rotates in a fixed nut in the movable jaw. The screw of
the vice may be square or buttress threaded.
 While clamping the work in the vice, parallel blocks are placed below the work
so that the drill may completely pass through the work without damaging the
vice table.
 The drill press vice may be plain , swivel or angle vice. In a universal type
vice the base may be swiveled at any angle about the vertical axis and it may
be tilted in a vertical plane to drill holes at an angle.

Types of Vices
41
(c ) Angle vise
Angular adjustment on base to allow
operator to drill holes at an angle
without tilting table

42
T-Bolts and Clamps
 tables are provided with T-slots into which T-bolts may be fitted.
 A slot or opening is cut at the centre of the clamp or strap to allow
the T-bolt to pass through it.
 The clamp is made to rest horizontally on the work surface and a
clamping block and the nut is then tightened.
 The T-bolt must remain as close to the work as possible. Some of
the common types of clamps are:
 T-Bolts
 Finger Clamp
 Goose Neck Clamp
 Adjustable step clamp
 U-Clamp

Various types of Clamps
43
Clamps or straps
 Used to fasten work to table or angle plate for drilling
 Usually supported at end by step block and bolted to table by T-bolt that fits into
table T-slot
Gooseneck Clamp
Adjustable Plain Clamp Adjustable Gooseneck Clamp
Step Clamp

In a suitable jig clamped on the bed
 Used in production for drilling holes in large number of
identical parts
 Eliminate need for laying out a hole location

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

Unit 3A2 - Drillling and related operations

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Unit 3A2 - Drillling and related operations