General Purpose Tools
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.
Use. These are used for driving or turning screws.
Material. Blade is made of high carbon steel, point / tip hardened and tempered. Handle is made of wood or composite material.
Classification. These are classified by type and the length of the blade.
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.
(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.
(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.
(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.
Use. These are used for gripping, holding and also for cutting purposes.
Material. These are generally made of high carbon steel with hardened and tempered jaws.
Classification. Pliers are classified by type and overall length.
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.
(b) Flat Nose Pliers. These pliers are used for holding and gripping thin and flat objects.
(c) Round Nose Pliers. These pliers are used for bending wires.
(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.
(e) Eye-let Fixing Pliers. These pliers are used for fixing eye-lets.
(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.
Use. These are used for cutting wires, rivets, nails, etc.
Material. These are made of high carbon steel and the working ends are hardened and tempered.
Classification. Cutters are classified by type and overall length.
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.
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.
Classification. Hammers are classified by the type and weight of the head.
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.
(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.
(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.
(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.
(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.
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.
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.
(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.
(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.
(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.
(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.
NOTE. A good centre punch can be made from old round file, ground to shape and suitably tempered.
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.
Classification. Drifts are classified by type, diameter, length and material.