Mechanical tools

. purpose of heat treatment . purpose of annealing . difference between the processess of annealing and normalising The properties of steel depend upon its composition and its structure. The properties of steel and its structure can be changed by heating it to a particular temparature and then, allowing it to cool at a definite rate. The process of heating and cooling for changing the structure of steel,and thus obtaining the required properties is called ' heat treatment of steel '. If steel is heated to a suitable temaprature, and then, slowly cooled, the steel will be soft, weak and ductile. If steel is heated to a suitable temaprature, and then, rapidly cooled (quenched) the steel will be hard and brittle. Classification of heat treatments The treatments that produce equilibrium conditions are annealing and normalising. Treatments that produce non-equilibrium conditions are hardening and tempering (usually done in conjunction with each other) Annealing In this process, stee...

.   structural changes of plain carbon steel while heating . the structural changes of plain carbon steel in normal cooling Distinguish between the lower and upper critical temparature during heating and cooling. Heating While heating uniformly a piece of plain carbon steel in a furnace, the temparature will increase uniformly and it will be halted or will fall slightly for a short time although the heat is supplied to the steel. At this point, the heat, is being used to  cause a rearrangement of the iron atoms which, in turn,, causes the formation of a solid solution called austenite. The temparature at which austenite is formed is called the lower critical point (heating ) and is at 723°c. If the steel contains less than 0.83% carbon there will be some ferrite present after the above change also. And if it contains more than 0.83% carbon, there will be some cementite present after this change. If the heating is further continued, the ferrite or cementite present will be grad...

. The different methods of identifying ferrous metals and alloys . state how non ferrous metals and alloys are identified A fitter has to handle different types of metals in his  work. A knowledge about how to recognise and differentiate the commonly used metals will help him in many ways. Ferrous metals and alloys can be identified by Their appearance (colour, texture etc,) Their weight (light or heavy ) The sound Cold hammering The spark test (grinding ) Apart from the above tests steel bars are also identified by the code colours painted on them. Different colours are marked, based on the different composition of materials and grade. Colours charts are available to determine the different metals. Most non ferrous metals and alloys can be identified by their colour. copper colour is distinctive red colour Aluminum colour is  dull  white Lead colour is bluish grey colour Tin colour is silvery white, with a slightly yellowish tinge Brass colour is distinctive yellow colou...

The principle of the L. D converter Name the raw materials used for the charge in L.D process👍 L. D. Process The name L.D. is derived from the initials of two towns,LINZ & DONAWITZ in Austria where this process was first used. The L. D. is converter or the basic oxygen converter is designed to produce high quality steel in a relatively shorter time. The basic raw material used in the process are the molten pig iron from the blast furnace and the steel strap. Fluxing agents are used for reacting with impurities and form a slag on the top of the molten metal. In this process of 👍producing steel, a jet of pure oxygen is blown through a lance which is water cooled.The lance is brought near the molten metal and oxygen is blown at high pressure on the molten metal bath. This leads to the oxidation of carbon and other impurities causing violent agitation which allows all the molten metal to come in contact with the oxygen stream. When the blowing is over,the converter is tipped to remov...

.The different manufacturing processes of steel . manufacturing process of steel by the bessemer process . distinguish between acid process and basic process Manufacturing processes The different manufacturing processes of steel -Bessemer process -L. D process -Electric process -Open hearth process Bessemer process Sir Henry Bessemer, a British engineer invented this process of converting molten pig-iron to steel  using a large pear shaped container. This is called the Bessemer converter. It is a method of producing steel by blasting compressed air through molten iron and burning out the excess carbon and other impurities. This does not use any source of heat other than obtained from the oxidising process used to remove carbon and other impurities. The three stages of this process are -the preliminary stage (The slag formation ) -the boil stage (The brilliant flame blowing period) -the finishing stage (The reddish smoke period ) The molten pig iare from the blast furnace is poured ...

  Colouring of metals . methods of colouring by heat .different methods of colouring metals . method of blackening /black oil finishing of metal surfaces Machined or filled ferrous metal  surfaces can be colored by the following methods. Heating and cooling Application of chemicals Colouring by heating Attractive colours can be given to metals by  heating. In this process, the metal surface to be treated is thoroughly polished. The metal is then placed in a heat treatment oven or flame heated. During the heating of the metal, watch the colours as they appear. When the desired colour is seen, remove and quench suddenly in water or oil. Rub gently with steel wool. Black oil finish For blackening the surface of a ferrous metal, first clean the surface thoroughly, and apply a coating of thick lubricating oil. Then heat the metal to 150° to 175° c for about 5 to 8 minutes. This will give a black and rust preventing coating on ferrous metal surfaces. Chemical colouring Polished...

. different angles formed at the cutting edge of tools . the important of clearance and rake angles in metal cutting Metal cutting Knowledge about the principal for metal cutting relating to the various tool angles will assist in carrying out of metal cutting work efficiently. Workpiece are shaped and brought to the required dimension by the use of cutting tools. While cutting materials the following four important elements interact. Cutting tool Tools holding or grinding device Work holding devices, and work Although the metal cutting process involves the combination of the above four elements, everything begins with a cutting tool and its impact at the time of contacting the workpiece. The common metal cutting processes are carried out either by the  use of a single point or multi point cutting tools. Cutting edge are taken as the factors for determining the tool life, surface finish, and the force required for cutting. The important angles of the cutting edge are Clearance angle...

Different types of cutting saws Advantages of a horizontal band saw Different types of cutting saws Metal cutting saws of different types are used in industries. The most commonly used are the Power saw Horizontal band saw circular saw Contour saw Power saw This is the most commonly used metal cutting saw. Horizontal band saw This has a saw frame on which a motor is  fitted. There are two pulley wheeels on which an endless band saw passes. Speed variation is obtained through the stepped pulleys on the motor. The roller guide brackets provides the rigidity for the blade in the cutting area and also prevent wandering of the blade while cutting. The blade tension is maintained by using the adjusting handle, provided for this purpose. A vice is provided for holding the metal stocks. The vice is adjustable for angular cutting. The machine has the advantage of continuous cutting ability, and is much faster than a power saw. It may be noted that a power saw cuts only in every alternate st...

Features of power hacksaw features of a power hacksaw . correct blade of different types . features of power hacksaw blade Cut-off saws are used to cut metal stock roughly to the required length. 🤺 commonly used to cut off saw in small scale industries is a POWER SAW. Power hacksaw Features The power saw works like a handsaw, and has an arrangement for cutting during the movement in one direction and releasing pressure on the non-cutting stroke. The rotary motion of the motor is converted into linear motion by a crank mechanism. The required cutting pressure is obtained hydraulically or by an adjustable weight. During the non-cutting motion the blade will be lifted away from the work. A clamping device /vice holds the work firmly. Power hacksaw blades The saw blades are selected, depending on the machine and the type of work on hand. The blades are made of H. S. Steel and are fully hardened. For different materials, blades of different pitches are used (number of teeth per 25mm length...

. parts of a telescopic gauge . constructional features of telescopic gauges . parts of a small hole gauge Telescopic gauges are popular for fine work as they are very rigid and have a better 'feel'. Uses Used for measuring the sizes of holes, slots and recesses. Construction Telescopic gauges are 'T' shaped. They consist of a pair of telescopic legs or plungers connected to a handle. The plungers are spring loaded to force them apart. After inserting the gauge in a hole or slot, it can be locked in position by turning the knurled handle. It may then be withdraw from the hole and measured with a micrometer. Telescopic gauges are available in a set of 5 nos, to measure holes from 12.7mm to 152.4mm. No.1 12.7mm to 19mm No.2 19.0mm to 31.7mm No.3 31.7mm to 53.9mm No.4 53.9mm to 88.9mm No.5 88.9mm to 152.4mm Small hole gauges Telescopic gauges are not suitable for measuring holes below 12.7mm. For measuring smaller holes and slots, small hole gauges are used. Construction A...

Wrought iron manufacturing process of wrought iron . properties and uses of wrought iron Wrought iron is the purest form of iron. The analysis of wrought iron shows as much as 99.9% of iron. When heated, wrought iron does not melt, but only becomes pasty and in this form it can be forged to any shape. Modern methods used to produce wrought iron in large quantities are the -pudding process -aston or byers process Pudding process Wrought iron is manufactured by refining pig-iron. By refining pig-iron silicon is removed completely, a greater amount of phosphorus is removed, and graphite is converted to combined carbon. The above process is carried out in a pudding furnace. Pudding furnace This furnace is a coal-fired reverberatory furnace. The term reverberatory is applied because the charge is not in actual contact with the fire, but receives its heat by reflection from the dome shaped furnace roof. The product obtained is taken out from the furnace in the form of balls (or blooms) havin...

. different types of cast iron . properties of each type cast iron Cast iron is an alloy of iron, carbon and silicon. The carbon content ranges from 2 to 4%. Types of cast iron The following are the types of cast iron. -Grey cast iron -White cast iron -Malleable cast iron -Nodular cast iron Grey cast iron This is widely used for the casting of machinery parts and can be machined easily. Machine bases, tables, slideways are made of cast iron because it is dimensionally stable after a period of  aging. Because of its graphite content, cast iron provides an excellent bearing and sliding surface. The melting point is lower than that of steel and as grey cast iron possessses good fluidity intricate casting can be made. Grey cast iron is widely used for machine tools because of its ability to reduce vibration and minimize tool chatter. Grey cast iron, when not alloyed, is quite brittle and has relatively low tensile strength. Due to this reason it is  not used for making components ...

. commonly used ferrous metals . main raw materials used for the smelting of pig-pron and their uses . constructional features of  a blast furnace . properties and uses of pig iron Metals which contain iron as a major content are called ferrous metals. Ferrous metals of different properties are used for various purposes. The ferrous metals and alloys used commonly are -pig iron -cast iron -wrought iron -steel and alloy steels Different processes are used to produce  iron and steel. Pig-iron obtained by the chemical reduction of iron ore. This process of reduction of the iron ore to pig-iron is known as SMELTING. The main raw accoutrements needed for producing gormandizer-iron are  -iron ore -coke -flux IRON ORE The cheif iron ores used are -magnetite -hematite -limonite -carbonite These ores contain iron in different proportions and are 'naturally ' available. COKE Coke is the fuel used to give the necessary heat to carry on the reducing action. The carbon from the coke i...

Plastics . types of plastics . differentiate between thermoplastics and thermosetting plastics The dictionary meaning of plastic is 'capable of being easily formed or moulded'. There are a number of synthetic materials available under the name of plastics. Plastics have their origin in the chemical synthesis of materials from different sources like -agriculture -agriculture and petroleum -petroleum and coal -petroleum and mineral -minerals Of these, coal and petroleum are mostly used in making plastics Plastics are divided into three major categories -thermoplastic -thermo-setting plastics -elastomers Thermoplastics These are formed into shape by the application of heat and pressure. They soften when heated, and become solid agian when cooled. There is no chemical change in the moulding operation. Thermoplastics are -nylon -polythene -polypropylene -polystyrene -poly vinyl chloride -acrylic resin -cellulose Nylon(polymide) It is strong, tough and of light weight. It has a good ...

  Lathe accessories -4 jaw and 3 jaw chuck . corridor of a 4 jaw chuck and 3 jaw chuck .features of a 4 jaw chuck and 3 jaw chuck   4 jaw chuck The four jaw chuck is also called as independent chuck, since each jaw can be acclimated singly; work can be trued to within0.001"or0.02 mm delicacy using this chuck.   This type of chuck is much more heavily constructed than the tone- centering chuck, and has much lesser than holding power. Each jaw is moved singly by a square thread screw. The jaws are reversible for holding large periphery jobs. The independent 4 jaw chuck has four jaws, each working singly of the others in its own niche in the chuck body and actuated by its own separate square threaded screw. By suitable adaptation of the jaws, a workpiece can be set to run either true or eccentric as needed.   To set the job for the alternate time, it can be trued with the help of a dial test index.   The check on the workpiece should be carried out n...

  Feed mechanism of lathe . the parts of the feeding mechanism . functional features of the feeding mechanism Feed mechanism The feed mechanism of a lathe enables automatic feeding for the tool longitudinally and transversely as needed. By automatic feeding the finish on the work will be better, the feeding of the tool will be at a uniform by continuous rate and it takes less time to finish the operation while manual labour is avoided. The feed mechanism comprises Spindle gear Tumbler gear unit Fixed stud gear Change gear unit Quick change gear box Feed shaft/lead screw Apron mechanism The proportionate tool movement for each revolution of work is achieved through all the above units of the feed mechanism. Spindle gear The spindle gear is fitted to the main spindle, and it is outside the headstock casting. It revolves along with the main spindle. Tumber gear unit The tumbler gear unit itself is of three gears, having the same number of teeth and  it contacts the  spindle ...