A maintenance man should be well aware about the ratings of various types of electrical appliances. This knowledge will help him in the following ways- Select proper type of wire and other electrical wiring accessories. Lamp data for general lighting service lamp.
Fixing Handle to the Head:
There is a right and a wrong way of doing this. Trim the end of the handle so that it fits closely into the eye. Make an oblique saw-cut as deep as the thickness of the head. Because the eye-hole is tapered, the handle will not pull out when wedged wrong way and its results.
The centre line of the handle should be at right angles to both the length and the width of the hammer-head; and the greater dimension of the handle should be in the direction of the length of the head.
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The wedge is generally of hard wood but sometimes of steel. The handle is usually made of a durable shock-absorbing wood, and is shaped to give a comfortable grip.
Holding a Hammer:
The way to hold a hammer when doing work which requires average force and precision skilful handling results from trained coordination of hand and eye. The rigid handle enables the worker to control the force and direction of the blow. In giving a proper swing the arm pivots at the shoulder, elbow and wrist. The hand should be kept close to the body.
If properly used, the wear on a hammer will occur exactly in the centre of the face. The purpose of the crown on the face is to allow for variations. It helps also in stretching the metal.
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Good hammer-head are made of tool steel. Do not hit hard steel with a hammer, for the fare may break into pieces and injure somebody.
The Cross-Cut Chisel with an edge % in or 3/8 in wide is used for cutting grooves and key-ways. For about an inch above the cutting edge the chisel becomes narrower in order to let it work freely in the groove it is cutting.
In chipping a surface of large area, make parallel grooves across the surface with the cross-cut chisel and the use the flat chisel to reduce the reaming high parts.
Cutting angles of Cold Chisels:
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The cutting angle B, the angle of clearance C and the relief angle A. A typical cutting angle is 60°, but may vary several degrees either way.
The best cutting angle depends on the carbon content, hardening and tempering of the tool, and the nature of the material being worked upon. The harder the material, the blunter the cutting angle. The following are the best cutting angles for different materials:-
Grinding:
While grinding, be careful to press the chisel on the face of the grinding wheel at the correct angle. The surface of the wheel should run away from, not towards, the cutting edge. Move the chisel across the face of the wheel to dissipate heat, and use a gauge to check the angle after grinding.
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The edges of Flat and Cross-Cut Chisel should be slightly rounded. This ensures smooth chipping, because the corners of the chisel do no dig deeply into the work and are themselves not so liable to break.
The use of the Chisel and Hammer:
The breadth of a chisel has an effect on its action. As considerable force is needed to chip steel and wrought iron, which are of close structure, a narrow chisel is preferable but cast iron and brass can easily be chipped with wide chisels.
The cold chisel is struck with a hand or chipping hammer. Hold this chisel at such an angle with the work as to obtain an even chip of the right depth. Keep your eye on the cutting edge of the chisel and not on its head. .
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Chisels may be used to cut wires, small rods, bolts, rivets etc. Small pieces of metal up to 1/10 in, thick can often be held in a vice while being so cut. When sheet metal is being cut with a chisel it should be placed on a that flat cast iron or mild steel block not on wood and show chisels used for cutting iron bars and circular ends.
It consists of a narrow blade of good, hard, tempered alloy steel with set teeth, held in a metal frame having a means of applying tension on the blade. Sizes of blades are indicated by the length in cm. between the centres of the two holes in them.
Some hacksaw frames are adjustable for different lengths of blade. Ordinarily the depth of cut is limited to the gap between the blade and the frame. But in many frames the position of the blade can be changed and longer lengths can be adjusted.
The Blade:
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The usual style of teeth is 14 per inch, suitable for cutting soft steel, cast iron, etc. For softer metals, such as brass and aluminum, coarser teeth, about 12 per inch, are required, while for hard steel, tool steel, tubing, conduit and thin sheet metal, finer teeth, 18, 24 or even 32 per inch, must be used.
A flexible blade has only the teeth hardened and will withstand more bending without breaking than blades hardened throughout their depth.
The blade is fixed to the frame with the teeth facing forward, i.e. away from handle, and should be tightened so that is gives a musical twang when lightly plucked by the finger. The saw will be damaged by excessive tightness or looseness, and the latter often causes a twist in the cut.
The end attachment of the blade is shown in sufficient rake or tilt should be given to the pin to ensure the blade does not come off when sawing.
To handle the Hacksaw:
The action of sawing is very similar to that of filing. Mark the course of the desired cut by a guide line on the work and make a nick with a file at the further edge of the work. Hold the handle in the right hand and the front end of the frame in the left. Place the feet so that the body is well balanced.
Start sawing gently at the nick, keeping the blade, slightly inclined to the horizontal and in line with the guide-line. Proceed with light pressure and steady strokes, and gradually bring down the saw to the horizontal position so that it cuts exactly along the guide-line.
Keep the blade perfectly vertical and avoid twisting it sideways; use the full length of the saw at each stroke. Put sufficient pressure on the forward stroke to make the teeth cut, but no pressure should be Put on the backward stroke.
If the saw glides across the work without cutting, the teeth will soon get blunt. For soft metals a suitable speed is 60 strokes/minute but for harder metals only about 20 strokes/minute.
Although tool steel can be ground on a stone, it cannot be cut by either a chisel or a saw when it is hardened. If an attempt is made the tool will be damaged. Tool steel can only be cut in the annealed condition.
Point to Notice:
To avoid breaking the saw or bending the work when cutting thin tubes or thin pieces of metal, place a piece of wood behind the work and hold both together firmly in a vice. A coarse blade is suitable for thick material but will break when used on thin work. The blare should always be course enough for the chips not to clog the teeth.
Always use a sufficient large twice blade to have at least 2 teeth on the work. The teeth enlarged and their cutting action. A new blade is thicker than a worn one so does not use a new blade in a cut made by an old one, or you will break the saw. If you have to use a new blade, start sawing afresh from the opposite side of the work
Manual crimping tools:
A range comprising of 2.5 sq. mm. to 400 sq. mm. (conductor size) M-Seal Manual Crimping Tools make jointing & terminating of Aluminum conductors easy and quick.
M-Seal MCT with its built-in ruggedness and design characteristics can be used with complete reliability even by unskilled personnel Solder/Flux for Al. etc. are made obsolete by M-Seal Manual Crimping Tools. Crimped joints/terminations made with MCT meet all performance criteria stipulated in IS-8337.
MCT have the following advantages over hydraulic tools:
(1) No maintenance problems like leakage of oil and consequently inability to build up necessary pressure.
(2) More compact and lighter weight enabling easy transportation to site and ease of use.
(3) Very competitive price as compared to hydraulic tools.
(4) Can be easily used for making straight through joints due to streamlined and compact design of jaws.
(5) Positive mechanical action through a double fulcrum ensures compression of the lugs/ferrules to the correct depth.
MCTs are supplied in light weight rexine cases and are available in the following sizes:
Instruction for Use (For MCT -185 and MCT – 400):
March the dies slot with the holding plates and tight the nut, taking care that the die does not shift away. To remove the die, loose the nut and push plate’s 3-4 mm. downwards and by tilting the die outward from the top, remove it.
M-Seal Corrosion Inhibiting Compound is suitable for removal of Al. Oxide film on Al. conductors. It can be used with Al. lugs/ferrules for Al. conductors and has been developed to meet the requirements of relevant Indian Standards.
Kinds of Punches:
Blacksmith’s punches are fitted with handles and are lightly hammered into the hot metal, first from one side and then from the other.
Drifts are short tapered tools for finishing punched holes. Punches and drifts are made in various sizes and shapes to suit the blacksmith’s needs. Use a punch one size smaller than the required size of the hole
Sheet Metal Punches are either solid or hollow. Small holes are made with the solid punch; larger hole with the hollow one which has a cutting edge at its face. The work is laid on a wooden block or on a piece of lead when being punched.
A Rod Punch is used for driving pins out of holes. Unlike other punches it is made of soft metal, such as brass or copper, to prevent damage to the bolt or pin. It should be rather smaller than the hole in the work.
The Center Punch and the Dot Punch are used for marking out on metal, and are of hardened, tempered, tool steel. Their points are actually cones ground to angles of 60° and 90° respectively.
The centres of holes are marked with a centre punch preparatory to drilling the punch mark should be correctly positioned and be large enough to take the nose of the drill. Grind the centre punch as in with the grind-
The wires can be specified either according to the type of conductor or the type of insulation. The usual way to specify the wire is with the reference to the insulation, size and number of cores. The wire gauge is British Standard wire gauge.
(i) Heavy duty cable:
Partly each conductor has dielectric & remainder dielectric in the form of over belt.
(ii) Screed cable:
Conductor is covered by layer of semi conducting paper to smoothes out the conductor surface.
(iii) Weather proof PVC single or twin core:
Batten wiring cleat capping conduit cable. Wiring casing & capping wiring copper conduit wiring IS 3035 250/440v 650/11000v. TVC is harder than rubber Polyethene insulated & sheathed cables. Polythene has got better insulation properties then PVC.
(iv) Weather proof cable:
Cotton braiding – Treated with paper insulation screening of metalized paper. Thin aluminums foil struck to copper.
Three cores are stranded together with jute or paper wrapped with a binder of fabric tape interwoven with copper or aluminum strands. Lead sheath bedding armoring & serving are provided.
Type of Wires as Per Construction:
Following are types of wires-
(i) Solid conductor-copper, Aluminum.
(ii) Flexible wire – number of wires stranded together. 3/20 means 3 wires of 20 S WG.
1. P.V.C. (Poly Vinyl Chloride) Wires:
In this type of wires, conductors are insulated with P.V.C. insulation. Nowadays, these wires are used for mostly batten wiring, cleat wiring, casing capping wiring and conduit wiring. P.V.C. insulation is harder than rubber, so cotton taping and braiding is not required for mechanical and moisture protection. These wires should not be used for giving connection to the heating appliances and pendent lights etc.
2. Weather-proof wires:
These wires are used for outdoor work as service lines. The conductors are insulated first with rubber, then braiding of cotton thread. The braiding material is dipped in waterproof compound.
3. Flexible wires:
These wires are used for giving connection to heating appliances, pendent lights, portable appliances etc. The insulation used is pure rubber or vulcanised rubber on which single or double cotton or vulcanised rubber on which single or double cotton or artificial silk braiding is provided or only PVC is used.
4. V.I.R. (Vulcanised India rubber) wires:
These wires can be used for general electrical wiring in casing capping and conduit wiring. These wires absorb moisture quickly, these are obsolete now.
5. C.T.S./T.R.S. (Cab Tyre sheathed/Tough Rubber sheathed) wires:
These wires are somewhat moisture-proof. These are available in single core, twin core and three cores. These are also obsolete nowadays.
6. Lead sheathed wires:
Such types are similar in construction with T.R.S. as far as core section is concerned but having outer sheath of lead or lead alloy. These wires are used for the moisture full weather and for the snowfall area.
7. Eureka wire:
It is used in theostates which are used for variable resistance in the circuit.
8. Nichrome wire:
It is used as a heat-producing resistance in heating appliances.
9. Hard-drawn bare copper conductor:
It is used in over-head lines and earth connection wires.
10. Aluminum conductors:
It is used in overhead lines. Now-days it is used as well in V.I.R. wires, C.T.S. wires and P.V.C. wires.
11. Enameled wire:
It is used for winding all types of electric motors and generators. It is also used for making electro magnets.