General Purpose Tools Required In Basic Workshop Technology

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Introduction
1.            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.
2.            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.
3.            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                                                                                                                                 


Fig 1 General Purpose Tools
4.         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. (Refer Fig 1)
Classification of Engineering Tools    
5.         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
General Purpose Tools
6.         The common type of general purpose tools and their uses are as follows:
(a)       Screw Driver.           It is used to turn the screws.
(b)       Plier.              It is used for gripping and holding thin jobs / objects.
(c)        Cutter.           It is used for cutting wires, rivets, etc.
(d)      Hammer.       It is used to deliver an impact to an object, to form shapes, to deliver blows, etc.
(e)       Punch.           It is used for marking out, locating centres, etc.
(f)        Drift.               It is used to finish off small non- circular holes, for driving pins out of the shaft and tight fitting parts, etc.
Screw Drivers
7.         Use.    These are used for driving or turning screws.
8.         Material.        Blade is made of high carbon steel, point / tip hardened and tempered. Handle is made of wood or composite material.
9.         Classification.         These are classified by type and the length of the blade.
10.       Types.           The different types of screwdrivers are described below:
(a)          Common Screw Driver  (CSD). The width of the tip varies with the length of blade. This is quite strong and used for rough work. (Refer Fig 2)

Fig 2 Common Screw Driver
(b)       Ratchet Screw Driver.           It enables the operator to use the screwdriver without changing the grip. It saves time and avoids damage to screw heads. (Refer Fig 3)   

Fig 3 Ratchet Screw Driver
(c)        Watch Maker’s Screw Driver.      These are available in various sizes and are used for intricate works only. It is also known as instrument maker’s screw driver. (Refer Fig 4)
                   

Fig 4 Watchmaker’s Screw Driver

(d)          Phillips Screw Driver (PSD).     The phillips screw driver tip is pointed and made after cutting four flutes. Such screw drivers are used where the screws have cross-shaped groove at their heads. The advantage is that the screwdriver cannot slip out of the slot. (Refer Fig 5)                               

Fig 5 Phillips Screw Driver

Pliers

11.       Use.    These are used for gripping, holding and also for cutting purposes.
12.       Material.        These are generally made of high carbon steel with hardened and tempered jaws.
13.       Classification.         Pliers are classified by type and overall length.
14.       Types.           The following are the different types of Pliers most commonly used:           
(a)       Side Cutting Pliers.  These pliers are used for cutting wires, cables, etc. (ReferFig 6)                                                                        

Fig 6 Side Cutting Plier

(b)       Flat Nose Pliers.     These pliers are used for holding and gripping thin and flat objects. (Refer Fig 7)
Fig 7 Flat Nose Plier
(c)          Round Nose Pliers.  These pliers are used for bending wires. (Refer Fig 8)
Fig 8 Round Nose Plier
(d)       Gas Pliers.    These are used for holding gas pipes, rods, etc.  Handle is insulated for electrical work. Plain handle is used for general work. (Refer Fig 9)

Fig 9 Gas Pliers
(e)       Eye-let Fixing Pliers.  These pliers are used for fixing eye-lets. (Refer Fig 10)
Fig 10 Eye-let Fixing Plier

(f)        Combination Pliers. The jaw of these pliers is so designed that it can be used for gripping flat objects as well as round objects. It can also be used for cutting wires and cables. (Refer Fig 11)                                                                           
Fig 11 Combination Plier


Cutters
15.       Use.    These are used for cutting wires, rivets, nails, etc. (Refer Fig 12)
16.       Material.       These are made of high carbon steel and the working ends are hardened and tempered.
17.       Classification.        Cutters are classified by type and overall length.
                        
Fig 12 Cutter
Hammers
                       
18.       Use.               These are used for causing a succession of blows to facilitate the fitting or removal of any part, item and component. These are also used for shaping and forming metals.
19.       Material.        Ball peen, Cross peen and straight peen hammers are made of high carbon steel hardened and tempered on face and the centre is left soft. The hammer shaft / handle is usually made of straight-grained ash wood to absorb the shock.
20.       Classification.         Hammers are classified by the type and weight of the head.
21.       Types.           Following are the types of hammers commonly used:
(a)       Ball Peen Hammer.            This hammer is also called engineer’s hammer. It is used for riveting, sheet metal work and forming work. (Refer Fig 13 & 14)
  

Fig 13 Ball Peen Hammer

Fig 14 Hammering Procedure 
                     
(b)       Cross Peen Hammer.               It is used for general work like bending and stretching. The narrow cross peen is suitable for work in narrow or curved places. (Refer Fig 15)
Fig 15 Cross Peen Hammers
(c)        Straight Peen Hammer.          The peen is parallel to the axis of the eye hole.It is used for peening, stretching the metal and riveting at awkward places. (Refer Fig 16)                                                                                                                                                                                                                                                
Fig 16 Straight PeenHammer
(d)          Hide Faced Hammer.           These are used where damage to the job must be avoided, e.g. shaping the sheet metal jobs, removal of ovality, dents and buckling.  The face is normally made of leather and the shaft is usually made of straight grained ash wood to absorb the shock. (Refer Fig 17)                                   
Fig 17 Hide Faced Hammer
(e)       Copper or Lead Hammer.            It is used where extra weight is needed, e.g. removal of ovality, dents and buckling. Their heads are made of copper or lead. (Refer Fig 18)
Fig 18 Copper Hammers

Punches

22.       Materials and Construction.  These are made of high carbon steel hardened and tempered at the working end. The shank is untreated to withstand the shock. The top end is slightly chamfered to prevent the edge from becoming battered from constant hammer blows. The shank is knurled or made hexagonal or octagonal in shape to provide a good grip. When using a punch, the tip of the third finger (ring finger) is held against the bottom of the punch in order to steady the point and prevent it from sliding off the mark. (Refer Fig 19)                                    
Fig 19 Punches
23.       Types and Uses.  The types and uses of the punches are as follows:
            (a)       Centre Punch
(i)         Light Centre or Dot Punch.         It is used for marking out series of light pops along marked lines, which will be machined or filed away. An angle of 60º is suitable for this purpose. It is used for light work. (Refer Fig 20)                     
Fig 20 Light Centre or Dot Punch
(ii)        Stout Centre Punch.          It is used to make heavy pop mark to locate drill at the commencement of drilling. An angle of 90º is suitable for this operation. (Refer Fig 2.21)
Fig 21 Stout Centre Punch
(b)       Pin Punch
(i)         Tapered Pin or Nail Punch.         It is used for punching holes in thin sheet metal and for removing taper pins. The point of the punch is made slightly concave to prevent it from slipping. It is classified by the diameter of the smaller end and overall length. (ReferFig 22)
Fig 22 Tapered Pin or Nail Punch
(ii)        Parallel Pin Punch.            It is used to drive out split pins (after the legs have been cut off), tight bolts, rivets, etc. It is important that the correct size of the punch should be used. The diameter should be just less than that of the pin to be driven out. It is classified by the diameter of the parallel end and overall length. (Refer Fig 23)
Fig 23 Parallel Pin Punch

(c)        Hollow Punch.         It is used for cutting washers and other materials like leather, jointing materials, sheet rubbers, etc. The angle of cutting edge should be about 20° to give a clean cut. When cut out, the pieces remain inside the punch and are pushed out from the top by the other pieces cut one after the other. The size is known by the inside diameter at the hollow end. (Refer Fig 24)    
   
Fig 24 Hollow Punch
NOTE.           A good centre punch can be made from old round file, ground to shape and suitably tempered.


Drifts

24.       Uses.             These are stout flat-ended punches of steel, brass, copper or Aluminium used for localising hammer blows and preventing damage to the job. These are used to finish off small non-circular holes, e.g. square, rectangular, and hexagonal. They are used for driving tight fitting parts. (Refer Fig 25)
25.       Classification.         Drifts are classified by type, diameter, length and material.                                                                                                                                                                                                                                                                                                                                   
Fig 25 Drifts
Care and Maintenance of General Purpose Tools
26.       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.
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