Introduction:-
·
The drilling
machine is one of the most important
machine tools in a workshop.
As regards its important
is second only to the lathe.
·
It was primarily
designed to originate a hole; it can perform a number of similar operations.
·
In drilling machine,
holes may be drilled quickly and at a low cost. The hole is generated by rotating edge of a cutting tool
known as ‘drill’, which exerts large
force on the work clamped to the table.
Types
of Drilling Machine:-
·
Drilling machines are
made in many different types and sizes, each designed to handle a class of work or specific jobs to the best advantages.
·
The different
types of drilling
machines are:
1.
Portable drilling machine 5. Gang drilling machine
2.
Sensitive drilling
machine 6. Multiple spindle drilling machine
A.
Bench mounting 7. Automatic
drilling machine
B.
Floor mounting 8. Deep hole
drilling machine
3.
Upright drilling
machine A. Vertical
A.
Round column
section B. Horizontal
B.
Box column section
4.
Radial drilling machine
A.
Plain
B.
Semi universal
C.
Universal
Portable
drilling machine:-
·
As the name implies
this type of drilling machine can be operated with ease anywhere in the workshop
and is used for drilling
holes in workshop
in any position which cannot be drilled in a standard
drilling machine.
·
Some of portable machine
are operated by hand power
but some of the machine
are driven by individual motor.
·
The maximum
size of hole it can accommodate is not more than 12 to 18 mm.
Sensitive
drilling machine:-
·
Sensitive drilling
machine is a small machine
designed for drilling
small holes at a
high speed in light jobs.
·
The base of machine
may be mounted on a bench or on a floor.
 |
| Sensitive drilling machine |
1 – Table, 2 – Vertical
drill spindle, 3 – Sleeve,
4 – Cone pulley, 5 – V Belt, 6 – Head,
7– Driving motor, 8 – Vertical
column, 9 – Base
·
It consists
of a vertical column, horizontal table, a head
supporting motor and driving
mechanism for driving and rotating
the drill.
·
There is no automatic
feed of drill spindle.
·
Drill is fed to the work by purely
hand control.
·
Hand feed permits the operator
to feel or sense the progress of the drill into work, so that if the drill becomes worn
out or jams on any account, the pressure on
the drill may be released immediately to prevent it from breaking.
·
Sensitive drilling
machine are capable
of rotating drills
of diameter from 1.5 to 15.5mm
Upright drilling machine:-
·
The upright
drilling machine is designed for handling medium
sized workpiece.
·
Its construction is
very similar to a sensitive drilling machine for having a vertical column mounted
upon the base.
·
But this is larger and
heavier than sensitive drilling machine and is supplied with power feed arrangement.
·
There are two types of upright
drilling machines.
1.
Round column
section or pillar drilling machine
2.
Box column section
 |
| Upright drilling machine |
1 – Bevel gear
drive to spindle, 2 – Spindle, 3 – Over head shaft,
4 – Back stay, 5 – Cointer shaft
cone pulley, 6 – Fast
and loose pulley,
7 – Table elevating
handle, 8 – Foot padel,
9 – Base, 10 – Rack on column, 11 – Table
elevating
clamp handle, 12 – Table clamp, 13
– Table, 14 – Column,
15
– Hand wheel forquick hand feed,
16 – Hand wheel for sensitive hand
feed
·
Round column section or
pillar drilling machine consists of a round column that rises from
the base which
rests on the floor, an arm and a round
table assembly and a drill head assembly.
· The arm and the table have
three adjustments for locating workpiece under spindle.
1.
Arm and table may be moved up and down on the column.
2.
Arm and table may be moved in arc up to 180o around the column.
3.
The table
may be rotated 360o about its own center.
· The construction of machine being
not very rigid so useful for lighter
work.
· The maximum
size of holes that the machine can drill is not more than 50 mm.
·
Upright drilling
machine with box column section
has the square
table fitted on the
slides at the front face of the machine column.
·
Heavy box column gives the machine
strength and rigidity.
·
The table
is raised or lowered by an elevating screw that gives
additional support to the
table.
·
This special
feature permits machine
to work with
heavier workpiece and
holes more than 50 mm diameter
can be drilled by it.
Radial
drilling machine:-
·
The radial drilling
machine is intended for drilling medium to large and heavy workpieces.
·
The machine
consists of a heavy, round,
vertical column mounted
on large base.
·
The column supports a
radial arm which can be raised and lowered and may be swing around to any position over the work bed.
·
The drill
head containing mechanism for rotating and feeding the drill is mounted on a radial arm and can be moved horizontally on the guide ways.
 |
| Radial drilling machine |
1 – Base,
2 – Column, 3 – Radial arm,
4 – Motor for elevating the arm, 5 – Elevating screw,
6 – Guide ways,7 – Motor for driving the drill spindle, 8 – Drill head,
9 – Drill spindle, 10 – Table
·
These movements
are useful to locate drill at any desired position.
·
When several
holes are drilled
on a large workpiece the
position of arm and the drill
may be moved from one position to other after drilling first
hole without altering
the setting of the workpiece.
·
In a Plain radial
drilling machine, provisions are made for vertical adjustment of the arm,
horizontal movement of the drill head along with the arm and circular movement of the arm in horizontal plane about the vertical column.
·
In a Semi universal drilling machine, in addition to the above three movement,
the drill head can be swung about
a horizontal axis
perpendicular to the arm. This
fourth movement of the drill head permits drilling
hole at an angle to the horizontal plane other than the normal
position.
·
In a Universal drilling
machine, in addition
to the above four movements, the arm holding the drill head may be rotated on a horizontal axis. All these
five movements in a universal drilling
machine enable it to drill on a workpiece at any angle.
Gang
drilling machine:-
·
When a number of single spindle
drilling machine columns
are placed side by side
on a common worktable, machine is known
as the gang drilling
machine.
·
The speed and feed of the spindle may be controlled individually.
·
This type of machine
is specially adapted
for production work.
·
A series of operations
may be performed on the work by simply shifting the work from on to other
position on the work table.
Multiple spindle drilling machine:-
·
The function
of a multiple spindle drilling
machine is to drill a number of holes in a
piece of work simultaneously and
to produce the same pattern
of holes in a number of identical pieces in a mass production work.
·
The spindles
are so constructed that their center distance
may be adjusted in any position as per requirement of various jobs.
Automatic drilling machine:-
·
Automatic machine
can perform a series of machining operations at successive units and transfer the work from one unit to the other automatically.
·
Once the work is loaded at first machine
then this will move from one machine
to the other where
different operations may be performed and finished product
comes out at last without any manual handling.
Deep
hole drilling machine:-
·
Special machined
and drills are required for drilling deep holes in rifle barrels,
crank shaft, long shafts etc.
·
The machine
is operated at high speed
and low feed.
·
For that work is usually rotated
while drill is fed into work and sometimes both work
and drill are rotated.
·
The machine
may be horizontal and vertical
type.
Size of Drilling Machine
·
The size of a drilling machine
varies with the type of machine being
considered.
·
A portable
drilling machine is specified by maximum diameter
of the drill that it can
hold.
·
The sensitive and
upright drilling machines are specified by the diameter of the largest piece that can be centered
under the spindle.
·
To specify
a drilling machine
fully further particulars such as the maximum size of
drill that the machine can operate, table diameter, the maximum spindle travel,
numbers of spindle speed and feeds available, Morse taper number of the drill spindle, power input, floor space
required, net weight of the machine, etc. are all needed.
·
The size
of the radial
drilling machine is specified by the diameter of the column
and length of the arm. Other particulars such as maximum drilling
radius, minimum drilling radius, spindle
speeds and feeds, etc. should
also be stated
to specify the machine fully.
Work Holding Devices:-
· Before performing any operation in a drilling
machine it is absolutely necessary to secure the work firmly
on the drilling machine table.
· The devices
commonly used for holding the work in a drilling
machine are:
T - Bolts and Clamps
Drill Press Vice
Step Block
V – Block
Angle Plate
Drill Jigs
·
One of the most common
methods of holding the work directly on the drilling machine table is by means of T - bolt and clamp.
The diameter
of T - bolts usually
ranges from 15 to 20 mm.
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