In engineering, particularly in heavy and medium engineering, even to-day, with the use of automatic machines, bench work and fitting have an important role to play to complete and finish a job to the desired accuracy. Although majority of the work can be finished to fairly good degree of accuracy in a reasonable time through various machining operations, still they require some operations to be done by hand to finish them to the desired accuracy. Much of the raw materials goes into the workshop and re-appears as a finished component ready for assembly. Some parts need both machining and then a certain amount of work in fitting, other parts are entirely made and fitted on the bench.
The term ‘bench work’ generally denotes the production of an article by hand on the bench. ‘Fitting’ is the assembling together of parts and removing metals to secure the necessary fit and may or may not be carried out on the bench. It is seen that there is no clear dividing line between these two terms and in most cases both terms are used rather loosely to define the same job.
However, all these two types of works require the use of a large number of tools and equipments and involve a number of operations to finish the work to the desired shape and size. The operations commonly used in bench and fitting work may be classified as:
(a) Chipping (b) Filing (c) Scrapping (d) Grinding (e) Sawing
(f) Marking (g) Reaming (h) Drilling (i) Tapping (j) Dieing
Normally all general operations on a job are performed by hand. But man needs various types of tools to carry out these operations. Some of the operations are cutting, filing, welding, polishing, etc. Tools, which are required to be used for general work, are known as general-purpose tools.
Classification of Engineering Tools
Tools are classified by the nature of jobs they perform, e.g.
(a) General purpose tools
(b) Shaping and cutting tools
(c) Marking and measuring tools
(d) Dismantling and assembling tools
Care and Maintenance of General Purpose Tools
The following care must be taken for maintenance of general purpose tools:
(a) Always use a tool for its designed or intended purpose.
(b) After using the tools, these should be placed in their respective places after proper cleaning and oiling whenever required.
(c) Do not mix cutting tools with measuring tools.
(d) Sharp edged tools are to be covered.
(e) Pliers used for electrical purpose should be properly insulated.
(g) Use correct size and maintain proper tip angle while using screw driver.
(h) Maintain the definite angle of centre punch.
(j) Keep the hammer head, punch and drift free from burrs.
(k) Ensure that the hammer head is firmly secured to the hammer handle
(l) Ratchet screw drivers are not as strong as CSD due to ratchet mechanism, which may break if unnecessarily more force is applied.