4. INTRODUCTION
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.
It is one of the most important and versatile machine tool in a workshop.
9. (a) General purpose
drilling machines of
common use
1. Table top small sensitive
drilling machine
These small capacity (Equal Or More
Than 0.5 kW) upright (vertical) single
spindle drilling machines are mounted
(bolted) on rigid table
Manually operated using usually small
size (φ More than 10 mm) drills.
10. 2. Pillar drilling
machine
These drilling machines, usually called pillar
drills, are quite similar to the table top
drilling machines but of little larger size and
higher capacity (0.55 – 1.1 kW)
Grouted on the floor (foundation)
These low cost drilling machines have tall
tubular columns and are generally used for
small jobs and light drilling.
11. 3. 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.
Such drilling machines are most widely used and
over wide range ( light to heavy) work.
12. 4. Radial drilling
machine
This usually large drilling machine
possesses a radial arm which along with the
drilling head can swing and move vertically
up and down as can be seen in Fig.
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.
There are some more versatile radial drilling
machines where the drill spindle can be
additionally swivelled and / or tilted.
13. 5. CNC column
drilling machine
In these versatile and flexibly automatic drilling
machine having box column type rigid structure
the work table movements and spindle rotation are
programmed and accomplished by Computer
Numerical Control (CNC)
These modern sophisticated drilling machines are
suitable for piece or batch production of precision
jobs.
14. (b) General purpose
drilling machines with
more specific use.
1. Hand drills
Unlike the grouted stationary drilling machines,
the 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
shown in Fig.
The small and reasonably light hand drills are
run by a high speed electric motor
In fire hazardous areas the drill is often rotated
by compressed air.
15. 2. Gang drilling
machine
In this almost single purpose and more
productive machine a number (2 to 6)
of spindles with drills (of same or
different size) in a row are made to
produce number of holes progressively
or simultaneously through the jig.
Fig. schematically shows a typical
gang drilling machine.
16. 3. 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.
These drilling machines are available with
varying degree of automation both fixed and
flexible type.
17. 4. 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. Such drilling
cannot be done in ordinary drilling machines and
ordinary drills.
It needs machines like deep hole drilling machine
such as gun drilling machines with horizontal axis
which are provided with
1.high spindle speed
2.high rigidity
3.tool guide
4.Pressurised cutting oil for effective cooling, chip
removal and
5.lubrication at the drill tip.
18. OPERATION ON DRILLING MACHINE
OPERATIONS PERFORMED ON DRILLING
MACHINE
A drill machine is versatile machine tool. A number of
operations can be performed on it. Some of the
operations that can be performed on drilling machines
are:
1. Drilling 2. Reaming
3. Boring 4. Counter boring
5. Countersinking 6. Spot facing
7. Tapping 8. Lapping
9. Grinding 10. Trepanning.
19. Drilling
1. Drilling removes solid metal from the job to
produce a circular hole.
2. 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.
3. A suitable drill is held in the drill machine and the
drill machine is adjusted to operate at the
correct cutting speed.
4. The hole, depending upon its length, may be
drilled in one or more steps. After the drilling
operation is complete, the drill is removed from
the hole and the power is turned off.
20. Reaming
1. This is the operation of sizing and finishing a
hole already made by a drill
2. Reaming is performed by means of a cutting
tool called reamer as shown in Fig.
3. Reaming operation serves to make the hole
smooth, straight and accurate in diameter.
4. Reaming operation is performed by means of
a multitooth tool called reamer.
5. Reamer possesses several cutting edges on
outer periphery and may be classified as solid
reamer and adjustable reamer.
21. Boring
1. Fig. shows the boring operation
where enlarging a hole by means of
adjustable cutting tools with only one
cutting edge is accomplished
2. A boring tool is employed for this
purpose.
22. Counter-Boring
1. Counter boring operation is shown in
Fig.
2. It is the operation of enlarging the end
of a hole cylindrically, as for the
recess for a counter-sunk rivet.
3. The tool used is known as counter-
bore.
23. Counter-Sinking
1. Counter-sinking operation is shown in
Fig.
2. This is the operation of making a cone
shaped enlargement of the end of a
hole, as for the recess for a flat head
screw.
3. This is done for providing a seat for
counter sunk heads of the screws so
that the latter may flush with the main
surface of the work.
24.
25. Lapping
1. This is the operation of sizing and
finishing a hole by removing very
small amounts of material by means
of an abrasive.
2. 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.
26. Core drilling
1. Core drilling operation is shown in Fig. 12.
2. It is a main operation, which is performed
on radial drilling machine for producing a
circular hole, which is deep in the solid
metal by means of revolving tool called
drill.
27. Application Of Drilling Machine:
The wide range of applications of drilling machines include :
Origination and / or enlargement of existing straight through or
stepped holes of different diameter and depth in wide range of
work materials – this is the general or common use of drilling
machines
Making rectangular section slots by using slot drills having 3 or
four flutes and 180 cone angle
Boring, after drilling, for accuracy and finish or prior to reaming
Counterboring, countersinking, chamfering or combination
using suitable tools.
