UNITS (SI)

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BOLTS AND NUTS

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A bolt is fastening element comprising of the head at one end a threaded portion over a cylindrical shank at the other end. The parts to be fastened temporarily by bolts and nuts admit hexagonal head   and Square head  are very common. although the square shape provides a better spanner grip than the hexagon, but needs one fourth of a turn to bring it into the same position for inserting the spanner again whereas a hexagon need only one sixth of a turn and hence preferred. the bolts through the holes in them having suitable clearance. The projected threaded end of the bolt in turn now admits the washer and nut an internally threaded member, which after sufficient turn offers necessary clamping grip. Bolts and nuts of various shapes are used fir different purposes but the        Empirical Proportions of Hexagonal Head Bolt and Nut All Dimensions in mm                            ...
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RIVETS AND RIVETED JOINTS

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Riveted joints: In riveted joints were classified as one of the types of permanent fastenings. They are generally used to fasten metal plates and steel section in structural works such as bridge and roof trusses and in the construction of pressure vessels such as storage tanks boilers. The field of application of riveted joints has been considerably reduced by the welded joints because of the simplified process of making the welded joint comparative strength and economy. However riveted joints are very effective in designs subjected to pronounced vibration loads where welded joints are less reliable. Riveted joints may also be employed to connect metals which are difficult to weld together and in the joints which permit no heating welded due to possible tempering or warping of the finished machine parts. Rivet: A rivet is a round rod of either mild steel or nonferrous materials such as copper aluminum with a head of any one of the shapes formed at one end during its ma...
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KEYS

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A machine derives the energy or power for its working from a prime mover. The power in the form of rotary motion is transmitted from the prime mover to the machine either by connecting the prime mover shaft directly to the machine shaft by a coupling or using intermediate machine elements such as gears or pulleys and belts or sprockets and chains. in all these cases the shaft is secured firmly to the flanges or gears or pulleys or sprockets which are mounted on it to prevent the relative rotation between the two a tight fit of the shaft in the bore will be usually insufficient to secure the shaft to the machine element which is mounted on it. Types of keys: Keys are classified into two main types (1) taper keys (2) parallel or feather keys. A tapered key is of rectangular or square section with uniform width and tapering thickness. It transmits the turning moment between the shaft and the part mounted on it without any rotational and axial motion between them a parallel key i...
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