Jig Boring Machine

The jig boring is the most accurate machine of all machine tools. This was first developed in the year 1910 in Switzerland and used as a locating machine. The real jig borer was first built in the year 1917 by Pratt and Whitney.

Jig boring machine is used for the production of jigs, fixtures, tools, and other parts. That requires a high degree of accuracy. They are defined by terms of highest accuracy through rigidity, low thermal expansion, and precise means of measuring distance for locating and spacing holes.

The machining accuracy is high, within a range of 0.0025 mm. A jig boring machine looks like a vertical milling machine. But so far its operation and accuracy are concerned that there cannot be any comparison between the two.

The spindle and other parts of the machine are much hard to resist deflection and the vibration is low. A Spindle runs in preloaded antifriction bearings. The spindle housings are made of invar having a very low coefficient of linear expansion.

Jig boring machines need to be operated in temperature-controlled rooms where the temperature can be kept constant. This is essential to prevent inaccuracy in the machine and in the work being manufactured due to the thermal expansion of the metal.

Parts of a Jig Boring Machine

Following are the parts of a jig boring machine:

1. Head-stock

2. Column

3. Bed

4. Pick-up devices

5. Table and saddle

1. Head-stock

It is also called the spindle head, it is fixed on the column in the front. The spindle is held in the shaft. As this shaft is moving upward and downward it becomes more like a telescopic mechanism.

2. Column

It is also a hollow component made of cast iron. It is supporting the headstock, guideways and vertical head gives axis for positioning.

3. Bed

The tools on which the machine is grounded is called a bed. It is made of cast iron which supports the pillar, saddle, control penal, and the whole machine.

4. Pick-up Devices

It is connected to the table and saddle. It is helping to control various machine operations automatically.

5. Table and Saddle

The table helps to fasten and hold the workpiece in a fixture in the required position. So it has T-shaped slots built into it. The saddle gives the longitudinal motion to the workpiece.

Working Principle of Jig Boring Machine

Jig boring machine works on the principle of feed in the vertical axis of the hole and its radius. In this process rotating tool is moved over the process is given with respect to static work.

This principle is used for large workpieces. Whereas the small size workpiece tool is kept stable and the work is done by applying force. Jig boring is a unique type of boring process. So its working principle is similar to the boring process. 

Types of Jig Boring Machine

There are mainly two types of jig boring machine:

1. Vertical milling machine type

2. Planer Type

1. Vertical Milling Machine Type

It relates in construction to a vertical milling machine. The spindle rotates on a vertical column and the horizontal table rests on the bed in front of the column.

The position of the work mounted on the table. It may be taken by compound moves of the table, perpendicular, and parallel to the column face.

2. Planer Type

It has two vertical columns on the two sides of the table and is fixed on the base. The table has a reciprocating action for adjustment of the work. The spindle is fixed on the crossrail bridging the two vertical columns.

In a planer type jig borer, two co-ordinate movements for hole location are given. By the longitudinal movement of the table and the cross movement of the spindle along the crossrail.

Methods of Locating Holes In Jig Boring

Holes should be bored on jigs and fixtures at distances from the two straight sides of the work. Exact positioning is essential for producing accurate jigs, fixtures, dies, etc.

The most important operation in a jig boring machine is the perfect way of positioning a hole. The perfect way of locating a hole in a jig boring machine may be secured by any one of the following methods:

1. Leadscrew method

2. Mechanical and electrical gauging method

3. Optical measuring method

1. Leadscrew Method

The leadscrew method is the most common and quick method of placing the work below the spindle.

Both longitudinal and crossfeed leadscrews are rotated by a specified value. Any error in the leadscrew due to backlash, wear, or manufacturing fault may be set by using a compensating device.

2. Mechanical and Electrical Gauging Method

Mechanical gauges such as gauge blocks or end measures are placed against a stop on the table. And a dial indicator is fitted at the outer end of the trough.

The motion of the table is now directed by the length of the end measures. The table may be set both in a longitudinal and crosswise direction to locate the exact hole. Electrical gauging devices are also sometimes used.

3. Optical Measuring Method

The scales used for measuring the motion of the table are enclosed within the machine to stop it from any harm or wear.

The motion of the table is set by the leadscrew or by hydraulic means. But the position of the table along the two axes is done by using the scale which may be seen through a microscope. 

Specification of Jig Boring Machine

Following are the specification of jig boring machine:

1. It has a maximum distance between the spindle face.

2. The distance of the spindle axis from the column.

3. The minimum distance between spindle, face table & various spindle speeds.

4. Least count of vernier caliper.

5. The minimum measuring capacity of a dial.

6. Horsepower of the table feed motor.

7. Horsepower of the main motor.

8. A maximum table transverse.

9. The dimension of the working axis of the table.

10. A maximum weight of work which can be placed.

Jig Boring Operations

The jig boring machines are made to produce precision dies, gauges, and jigs. They can also be used as a measuring machine to check up a job already manufactured in other machines.

Workpieces are clamped on the table by T-bolts and straps. And single point boring tools are used for enlarging holes. Single-point tools are favored than multipoint tools. As a single point tool allows maximum accuracy in locating holes and offers a better surface finish.

Applications of Jig boring Machine

Following are the applications of jig boring machine:

1. The jig borer is used for the pilot hole.

2. It is used to make compound and progressive dies.

3. It is also used for drilling holes in jig-bushing.

4. Jig borer is commonly used for jigs, fixtures and dies & bushing hole for grinding & A grinding the hardened parts.

5. Also used in alignment post in stripper or die set.

Advantages and Disadvantages of Jig Boring Machine

Advantages of Jig Boring Machine:

– High Precision: can create very precise and accurate holes with tight tolerances. 

– Versatility: can create holes with unique shapes or profiles that are difficult or impossible to create with other tools. 

– Increased Productivity: complete operations faster and with greater accuracy than other types of machines. 

– Reduced Waste: can reduce waste without the need for additional machining or adjustments.

Disadvantages of Jig Boring Machine:

– High Cost: they are typically more expensive than standard drilling or boring machines.

– Limited Capacity: have a limited capacity in terms of the size of the workpiece that they can accommodate.

– Specialized Training Required: require specialized training and expertise to operate effectively. 

– Limited Usefulness for Other Applications: are designed specifically for drilling precise holes and may not be as useful for other applications.

Jig Borer vs Milling Machine

Jig borer and milling machines are both machine tools used in metalworking to remove material from a workpiece, but they differ in their design and intended use. Here are some differences between a jig borer and a milling machine.

– Precision: Jig borers are designed to produce highly precise and accurate holes, while milling machines are designed for more general machining operations that may not require the same level of precision.

– Cutting tool: Jig borers use specialized cutting tools for drilling precise holes. Milling machines use a variety of cutting tools, including end mills, face mills, and drills, depending on the specific operation being performed.

– Control: Jig borers are typically equipped with more precise control systems than milling machines.

– Size: Jig borers are generally smaller than milling machines, which makes them better suited for drilling small, precise holes.

– Cost: Jig borers are generally more expensive than milling machines, due to their higher precision and specialized design.

Jig borers are preferred over milling machines when very precise and accurate holes are required, but milling machines are more versatile and can be used for a wider range of machining operations.