Types of Jig Boring Machines
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Types of Jig Boring Machines
Types of Jig Boring Machines - There are two types of jig boring machines.
(i) Single column jig boring machine.
Single Column Jig Boring Machine
(ii) Double column jig boring machine.
Double Column Jig Boring Machine
Single column jig boring machine is of open side construction. It has a. single column. The spindle head is supported in the vertical direction. The work spindle is held in accurate bearings. The workpiece is clamped on the machine table which is designed as compound table. This is adjustable length and crosswise.
Double column jig boring machine has a planer type construction. It has a (horizontal) cross rail that is supported and adjusted vertically on two columns. The cross rail serves to carry the vertical spindle in its housing along the transverse axis. The work table is like that of a planer. It is supported on the base of the machine and is movable along the longitudinal axis between the two columns of the machine.
A jig boring machine is provided with accurate means of measuring the longitudinal and lateral adjustments for boring various holes to given dimensions within close limits. For example:
(i) Some machines have precision lead screws with micro meter dials. One lead screw is for longitudinal and the other for cross-movements of the table. Though it is very quick method, it suffers from back lash and wear. A back lash eliminator may be used to advantage. The accuracy of lead screw is about 0'005 mm.
(ii) Another type of measuring device consists of vernier scales which show the lengthwise and lateral measurements.
(iii) A third method consists in using end measuring rods and micrometers between adjustable stops. To obtain greater refinement and insure uniform measuring pressure for all measurements, contact at one end may be with a dial gage.
(iv)In optical measuring method, accurately graduated scales fixed in the machine are used to measure the longitudinal and cross movements of the worktable. Measurements are taken with the help of a microscope.
A problem encountered in jig boring is the location of holes equally spaced on the circumference of a circle. The easiest way to do this is to use a rotary table. It is important that the pivot of the table be located in true alignment with the cutter spindle.
A jig boring machine is kept in an air-conditioned room to minimize the effect of ambient temperatures on the accuracy of various parts of the machine.
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