Jig Boring Machine

Jig boring machine:- Jig boring machine is the most accurate of all machine tools. It has first development in the year 1910 in Switzerland and used as a locating machine. A jig boring machine is a specially designed machine tool used for precision location and production of holes as are needed din jigs, fixture, templates, dies, gauges, etc. A jig boring machine is a precision boring machine used for boring accurate holes at proper centre to centre distances. The machining accuracy of holes produced by this machine is 0.00025 mm. very high with range 0.0025 mm. A jig boring machine resembles in appearance to a vertical milling machine, but so for its operation and accuracy are conceded there cannot be any comparison between the two. The spindle and other parts of the machine are extremely rigid to resist deflection and the vibration is minimum. The spindle runs in preloaded antifriction is bearings. The machine is also designed to be operated by numerical control.

Type of jig boring machine:

Vertical milling machine or single column type: The resembles in construction to a vertical milling machine. The spindle rotates on a vertical on a vertical column and the horizontal table rests on the bed in front of the column. The position of the work mounted of the table may be obtained by compound movement of the table, perpendicular and parallel to the column face.

Planer type or double column jig boring machine: It consists of two vertical columns at the two sides of the base. The table has reciprocating movement for adjustment of the work. The spindle is mounted on the cross-rail bridging the two co-ordinate movements for hoe location are provided by the longitudinal movement of the spindle along the cross-rails. 

Bed: The member that supports the machine is known as the bed. It is the lowest parts of machine and is made of cast iron . To increase the rigidity of bed it is provided with rids. It supports the all machine parts so also called “base”.

Column: It is hallow vertical cast-iron structure that supports the headstocks, guide ways and vertical spindle head. It is in corporate with the whole deriving mechanism of machine.

Saddle: It is mounted over the bed and is provided with guide ways for the movements of table. It is made up of cast iron block.

Table: It is mounted just over the saddle and move longitudinal, cross-wise as per the requirement. It is provided with t- slots for hold the job directly. It is also made of cast iron.

Quill: The spindle rotates within a non rotating sleeve which is known as the quill.

Write the system of measuring used in jig boring machine:- The principle of working of all jig boring machine is same but they differ in shape and sizes. So the jig boring machines is provided various systems of measurements:

Precision lead screw system: This system of measurement is providing underneath the table on jig boring machine. It consists of lead screw, graduated micrometer dial at its end a compensating device. The compensating device is used for correcting the errors in the table movements. The disadvantage of this system is that its use is limited to a small table.

End measurement of system: They are carries out by accurately finished rod with a view in standard length of ‘mm’ of is used for correcting the end measurement.

Scale and microscope system: In this system accurate gradated scale and a microscope is incorporate of the table. Measurements are performed accurate with a microscope. This system is very accurate and caring no wearing parts.

Electromagnetic system: This system consists of two arts at equipped magnetized projections. A precision micrometer screw is fitted just below the table. The screw is fitted at movable side and the end is fasted with magnetic chuck.

The different hole location procedure in jig boring machine: Before starting the any operation of drilling or boring the exact location of the position of work is very necessary. Following are the various method of whole location:-

Layout: It is the process in which we scribed a series of lines above the metal piece at the desired position with the help of precision instrument and punched marked are punched at the proper position and operations are carried out.

Buttoning: It is the process of locating the position by using toolmakers buttons. It is used for locating the position with great efficiency. It is available in standard sizes of 1 c.m x 1.5 c.m. x 2 c.m.

Transfer: This is the method of using a master plate for locating position. The master plate consists of a number of holes at suitably located position. It is a very quick method of locating the position of holes.

Co- ordinate location: This is the method of locating the position by using various measuring devices practically a height gauges.

Operation in jig boring machine: The jig boring machines are primarily designed 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. Work pieces are clamped on the table by t- bolts and straps, and single point boring tools are used for enlarging holes single points tools are preferred to multiple tools as a angle points tools enable maximum accuracy in locating holes and produces butter surface finish. 

Terminology of screw- thread:

NOTE:

P=PITCH

PD=PITCH DIAMETER

ROOT DIAMETER= PITCH/4

Fasteners: Fasteners are the means to join two or more components together.

Fastening: The act of joining the components with the help of fasteners is called ‘fastening’.

Temporary fastening or screwed fasteners: The parts or components to be joined are required to be separated periodically or frequently at will the method of joining the components in this manner is known as temporary fastening. The fastener used in this type of fastening are called temporary fasteners. Such as bolts, nuts, screws, studs pin, keys, cotters etc. are the “temporary fasteners”. 

Permanent fastener: In this sense, welding, soldering, brazing, riveting, etc. can all be considered as permanent fastening methods.

Threaded fasteners: Out of all the temporary fasteners the most widely used and effective fasteners are the threaded fasteners or screwed fasteners, i.e., those which carry threads for securing them in position. They category includes various types of bolts, nuts, studs, screw, etc.

Terminology of screw threads: A screw thread can be described as a ridge formed around the surface of a cylinder. It is in the form of a continuous helical or spiral groove, formed on the surface of a cylinder, such that the angular displacement of any two corresponding points on the contour of the groove is proportional to their displacement along the axis of the thread.