Mechanical tools

Specify rivets The common types of rivets and state their uses Rivets are cylindercal rods having heads of various shapes. Theys are used for assembling the parts of a workpiece together. Specification of a rivet The rivet is specified by the shape of the head diameter, and the length. Shape of head The shape of the rivet head is to be selected according to the intended use of the workpiece to be riveted. Diameter The diameter is to be selected depending on the required strength Length Length is to be selected depending upon the thickness of the components to be riveted Types and uses Snap head It is the most commonly used form, and it gives a very strong joint. Pan head It is used where strength is the only consideration such as heavy structural work . Conical head It is generally used in light assembly where riveting is done by hand hammering. Countersunk head It is used where projection of the rivet head is to be avoided. Bifurcated rivet The shape of the head is shown in the figure...

The different bending tools The uses of twisting and scroll bending The prevention of defects in bending Bending✌👰 Bending is a method of chipless shaping by which the external grain structure is lengthened 👉while the internal grain structure is shortened. Types of bending Bending to curve Bending to an angle BENDING TOOLS Vice or anvil edge An angle bend may be hammering in a vice or over the edge of an anvil. Bending block Bending blocks with lever and pegs are very convenient to use in a smithy. These are massive blocks pierced with holes in which pegs can be inserted. The work to be bent is placed between a series of pegs, already inserted in the holes, and the work is bent with a lever. Tool inserted in a hardle hole Some of the bending tools, like ring, mandrel are inserted in the hole of the anvil for bending the workpieces Beak of the anvil Curving of the workpieces can also be carried out on the beak of the anvil Bending links Bending links with top fullers are used for smal...

  The types of metals used in sheet metsl work The uses of the different types of metals In sheet metal work, different types of metals sheets are used. The sheets are specified by standard gauge munbers. It is very essential to know the different uses and applications of these metal sheets. Black iron The cheapest sheet metal is black iron, which is rolled to the desired thickness. It has a bluish black appearance, and is often referred to as  uncoated sheet. Since it is uncoated, it corrodes rapidly. The use of this metal is limited to articles that are to be painted or enamelled such as tanks, pans, stoves, pipes etc Galvanised iron Zinc -coated iron is known as galvanised iron. This soft iron sheet is popularly known as GI sheet. The zinc coating resists rust, improves the appearance of the metal and permits it to be soldered with greater ease. Because it is coated with zinc, galvanised sheet iron withstands contact with water and exposure of weather. Articles such as pans...

.Name the fuels used in hand forging . qualities of a good forge fire . the correct method of placing stock in fire For heating metals to be forged, different types of fuels are used. Fuels are combustible materials capable of generating heat energy. Forge furnaces are fired with petroleum gas, producer gas, oil, coal and charcoal. For hand forging, the hearths are heated with soild fuels like coal or charcoal with low sulphur content. For heating tools steels charcoal is preferred as the fire burns more evenly when charcoal is used. Heating and metal stock For efficient heating, the way in which the fire is maintained is important. Thr fire which is maintained on the top surface will be thin and not suitable for heating the metal to carry out forging. The fire should come from deep in the hearth. The forge fire should be maintained clean i.e, free from ash, clinkers and dust. Clinkers is formed as the coke burns. This settles down at the bottom of the hearth and solidifies. Accumulati...

. function of a forge . the parts of a forge and state their functions . identify the forge tools and state their uses The forge supplies heat for raising the temparature of the metal to be forged. Parts of a forge and their uses Hearth The hearth is the main part where the heating of the metal takes place. It is prepared with refractory (fire) bricks and clay. Tuyers The forced air is sent through the tuyers to burn the fuel. The tuyer covered with refractory materials to avoid melting. The air also passes through a cooling tank. Cooling tank To keep the tuyer cool always, the cooling tank is filled with cold water. Air valve The air valve is used to regulate the supply of air to the hearth Blower The blower supplies air to the forge for burning the  coal or coke. The blowers are operated manually or by electric Power. The blower is fixed independently to each forge or it supplies ait to a number of forges which are controlled by independent air valves. Hood and chimney Smoke and...

  The necessary of preheating high speed steel The hardening process of high speed steel High speed steels get their name from the fact that they may be operated as cutting tools at much higher speeds than is possible with plain carbon tool steels. Since the maximum hardness of high speed steels is  obtained on tempering at high temparatures, they can be operated as cutting tools in the same temparature range without loss of hardness. That is the rise in temaprature due to friction will not reduce the temper of the tool pointas it cuts into the steel. Tool steels are often annealed for softening before machining or forming, and also for obtaining grain refinement. An nealing Soak at 900° C for about four hours. Then cool slowly at not more than 20°C per hour to 600°C. It may then be cooled to room temparature in still air. Hardening Pre -heat to 850°C slowly to prevent cracking. Then heat rapidly to approximately 1250°C depending upon the alloy used. This rapid heating reduces...