Horizontal Boring Machine – Parts , Working of Boring Machine
Horizontal Boring Machine:
The horizontal boring mill is also known as horizontal boring, drilling and milling machine, and is intended to perform operations on relatively large pieces which cannot be rotated easily, are irregular and unsymmetrical, and require operations on many surfaces.
Fig. shows the main features of a horizontal boring machine. It also indicates the relative movements of its sliding and rotating elements. It may be noted that the main spindle can be rotated in either direction. It is possible to feed the main spindle axially. The work table can be traversed along and across the machine bed.
It is possible to machine a flat surface square with bored hole in one setting of workpiece by mounting facing head over the spindle.
The four basic types of machines are described below:
i. Table-Type Machine:
It is perhaps the most familiar machine and consists of headstock, column, base, table, saddle, end support and bed. The headstock can be raised and lowered, the spindle moved in and out, and the out board bearing moved up and down. The table and its saddle can be moved in two directions, so as to position the work conveniently. The end-support column can be positioned along the bed towards or away from the headstock.
ii. Floor-Type Machine:
It consists of headstock, column, column base, run way, end support runway and floor plate. The chief difference between this and the table-type machine is the spindle movement. The machine is used for heavier work. During the operation, the work is stationary and the spindle end support is traversed along the run-way past the work.
iii. Planer Type Machine:
It consists of headstock, column, column base runway, end support, end support run-way, table and bed. This type resembles with the table-type, but the work supporting mechanism is different. It has a reciprocating table very similar to the planer which makes it most suitable for big and long jobs.
iv. Multiple Head Type:
It consists of headstocks (two to four), columns (two), bed, table and cross-rails. This machine resembles the planer miller. It may have two, three or four headstocks, all of which may be swiveled for angular cuts. It is the only machine that can do vertical as well as horizontal boring of milling, e.g., boring and milling of V- type diesel engine blocks.
Boring tools are held in boring tool holders which may be either fixed or rotating type. Fixed holders are used in work-rotating machines and rotating holders in tool rotating machines. Size of boring bar should be such as to provide maximum rigidity and also permit sufficient clearance for disposal of chips. Normally boring bar diameter is taken as 0.7 x bore diameter. It should have minimum overhang.
Various types of boring tool holders are:
i. Adjustable Boring Bars:
These are built with cartridges (to hold throwaway type inserts) adjustable in axial and radial directions by set screws.
ii. Damped Boring Bars:
In it, dampers are provided at the feed end to absorb vibrations.
iii. Line Boring Bars:
These are used for long bores and can accommodate fly cutters, tool blocks, cartridges etc. These are supported at the feed end in suitable bearings.
iv. Boring Head:
It is more rigid boring tool holder and is used for roughing and finishing of large bore (100 to 500 mm). Provision to offset cutting axially and radially exists. Two cutters can be mounted radially at 180° to have balanced cutting.
v. Boring and Facing Heads:
This enables boring of large bores and facing of seating surfaces at right angles to the bore. Radial tool feeding facility also exists.
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