Jig boring machines are used to produce highly precise holes in components. They allow for greater accuracy of hole location, dimensions, and surface finish than other machining methods. Jig boring machines have heavy, rigid construction for stability. There are two main types: single column machines for small parts, and double column machines for larger workpieces. Boring tools are typically made of hardened steel or carbides, and come in various shapes suited for different boring applications. Jig boring involves rotating the tool to remove metal from a stationary workpiece, providing accurate hole features essential for parts like jigs, fixtures, and dies.

1. SIGMA POLYTECHNIC
Saini Tarandeep Singh (126420319613)
Department : Mechanical Engineering (19)
Sem : 5th Sem
Year : 2015-2016
Subject : Manufacturing Engineering – III
(3351903)

2. Jig Boring
Machines

3. The products we are using in our daily life consists of many holes in it.
Accuracy of their dimensions and quality is based on the process by which holes
are made in the product. In this the drilling is a main process. But the drilling is not
capable of producing holes of quality demanded by turbines and pumps. Hence the
boring holes in such cases is carried out. The boring increases the size of the
drilled hole plus increases the accuracy of holes as regards to their position and
geometrical dimensions.
The use of jig boring and jig grinding machines was started for overcoming
the limitations of skill of tool maker and for producing holes accurately and at
required position. Jig boring machine is similar to milling machine. But the work
produced by jig boring is quite precise. If spindle is rigid and machine itself is
massive, therefore the defects, deflection, vibration etc. developed due to change
in temperature is insignificant.
More precise and high quality holes are required in drill jigs, fixtures and
dies. The boring of such holes is called jig boring and machine on which this work
is done is called jig boring machine. It is a more precise vertical milling or boring
machine. The accuracy obtain on it is upto ± 0.0025 mm.
INTRODUCTION :

4. 1. Need :
The mechanism is need for establishing accurate relative position of
work and boring tool during the process and to obtain their relative motions
for the removal of metal. The boring operation can be carried out on lathe
and milling machine but the need of accuracy of holes, its quality and
relative position of different hole centres is demanded in jigs & fixtures. To
cope up with this work boring machines are needed, which are called “Jig
boring machines”.
2. Constructional Features :
Jig boring machine generally consists of a heavy base and a column. A
spindle head is provided at the top of this column, which is fixed on the
guide ways of the column. The spindle is fixed using preloaded antifriction
bearings which provides the characteristics like rigidity, wide range of
speed and production of less heat due to friction. The table is arranged on
the saddle. It can move in different direction on the guide ways of the
saddle. Table provides longitudinal motion to the work piece & saddle
provides cross movement to the work piece. By moving the spindle head
up and down, the vertical movement of the spindle is obtain.
NEED, CONSTRUCTIONAL FEATURES, WORKING PRINCIPLE AND
APPLICATIONS :

5. The type and dimension of jig boring
machine is based on the work done on it.
They are divided in two types as under :
1. Single column jig boring machine
2. Double column jig boring machine

6. SINGLE COLUMN JIG BORING MACHINE :

7. The line diagram of this machine is shown in figure.
It is made of plain rotary table, inclined table and square
table. It looks like a vertical milling machine, hence it is
called “Vertical milling type jig boring machine”. Its main
components are as under :
1. Bed
2. Column
3. Head – Stock
4. Table and Saddle
5. Pick - up devices
The single column jig boring machine is generally
used for boring of small components.

8. DOUBLE COLUMN JIG BORING MACHINE :

9. The vertical columns are provided at two
sides of this machine. This construction looks
like a planer hence it is called a “Planner type
jig boring machine”. Its line diagram is shown in
figure. Both the columns, supports the cross –
rails, on which spindle head is fitted. Table and
spindle head are arranged in accordance with
the position of the work piece. This machine is
more rigid from its constructional point of view.
Hence it can be used for boring the large weight
work pieces.

10. The jig boring machine is specified by following basis. It is also illustrated
in appendix given at the end of this topic :
 Distance of spindle axis from column.
 Maximum distance between spindle face & table.
 Minimum distance between spindle face & table.
 Diameter and taper of spindle hole.
 Maximum diameter that can be bored.
 Maximum weight of work which can be placed.
 Dimension of working axis of table.
 Maximum table transverse.
 Horse power of main motor.
 Horse power of table feed motor.
 Minimum measuring capacity (Least Count) of dial.
 Least count of vernier caliper.
 Various spindle speeds.
SPECIFICATION OF JIG BORING MACHINE :

11. Boring tools are made of H.S.S., carbides,
ceramics or diamond. The carbide tools are used
more due to their long life and they provides good
surface quality. The ceramics and diamonds are used
less for general types of work. The boring tool is one
type of single point cutting tool. It can be divided into
two groups based on its construction as shown in
figure.
1. Forged type boring tool.
2. Carbide tip tool.
Boring tools can also be divided into three
types as per their shapes as under.
1. Common type boring tool
2. Haviour cut boring tool
3. Special boring tool (To prevent striking of boring
bar with the work).
BORING TOOLS :

12. These tools are shown in figure :
TYPES OF BORING TOOLS AS PER THEIR SHAPES

13. The jig boring is a special type of boring process,
hence its working principle is just similar to that of
boring process. It is explained in figure with the help of
a line diagram.
3. WORKING PRINCIPLE OF JIG BORING PROCESS :

14. In this process rotating tool is passed over the stationary
work. This principle is used for large work pieces, while for small size
work pieces tool is kept stationary and work is moved by applying
force. The feed in this process is given with respective to the vertical
axis of the hole and its radius i.e. in two direction as shown in figure.
Due to this type of feed, sharp edge of the tool penetrates in the
work piece and metal is removed from it by the shearing action.
In this machine, setting is not done only by lead – screw
method again setting is not based on distortion of other parts of
machine under the action of force. Hence the setting is independent
of defect of screw, wear and distortion of parts, hence more accuracy
is obtained. For this precision measuring instruments are used in this
machine. The stresses and friction are insignificant in it. Hence
uniform position and condition is obtained in between two settings. In
this process precision lead screw, electrical gauging, optical and
digital measuring methods are used, by which accurate positioning
can be obtained.

15. The main functions of jig boring machine are as under :
I. Fast production of highly précised tools.
II. Provides accuracy of hole location & surface finish.
III.Establish more accurate relations between different
operations.
IV.It can produce delicate and complex components.
V. The components produced by this method can be used
for the purpose of inspecting parts produced by other
machines.
VI.The holes distorted during hardening can be corrected
by it. Again the grinding of taper hole, radial angle etc.
can be done by this process.

16. The applications of jig boring machines are as
under :
I. For Jigs, Fixtures and dies.
II.For drilling hole in jig – bushing.
III.To produce compound and progressive dies.
IV.For pilot hole & bushing hole for grinding &
alignment post in stripper or die-set.
V.For grinding the hardened parts.
4. APPLICATIONS :