Mechanical Guru's

CENTERLESS GRINDING MACHINE Centerless Grinding  is a machining process that uses abrasive cutting to remove material from a work piece. Centerless grinding differs from centered grinding operations in that no spindle or fixture is used to locate and secure the work piece; the work piece is secured between two rotary grinding wheels and the speed of their rotation relative to each other determines the rate at which material is removed from the work piece. Centerless grinding is typically used in preference to other grinding processes for operations where many parts must be processed in a short time. Process: In Centerless grinding, the work piece is held between two grinding wheels, rotating in the same direction at different speeds, and a work holding platform. One wheel, known as the grinding wheel (stationary wheel in the diagram), is on a fixed axis and rotates such that the force applied to the work piece is directed downward, against the work holding platform. This

ABRASIVES An  abrasive  is a material, often a mineral that is used to shape or finish a work piece through rubbing which leads to part of the work piece being worn away. While finishing a material often means polishing it to gain a smooth, reflective surface which can also involve roughening as in satin, matte or beaded finishes. Abrasives are extremely commonplace and are used very extensively in a wide variety of industrial, domestic, and technological applications. This gives rise to a large variation in the physical and chemical composition of abrasives as well as the shape of the abrasive. Common uses for abrasives include grinding, polishing, buffing, honing, cutting, drilling, sharpening, lapping, and sanding.  1.      Grit or grain : It indicates the size of the abrasive grains used in making a wheel. ·         Coarse wheels are used for fast removal of materials and for soft and ductile materials. ·         Fine grain wheels are used to grind hard and materia

PRINCIPLE OF DRILLING MACHINE  DRILLING DRILLING MACHINE IS ONE OF THE MOST IMPORTANT MACHINE TOOLS IN A WORKSHOP. IT WAS DESIGNED TO PRODUCE A CYLINDRICAL HOLE OF REQUIRED DIAMETER AND DEPTH ON METAL WORK PIECES.  THOUGH HOLES CAN BE MADE BY DIFFERENT MACHINE TOOLS IN A SHOP, DRILLING MACHINE IS DESIGNED SPECIFICALLY TO PERFORM THE OPERATION OF DRILLING AND SIMILAR OPERATIONS. DRILLING CAN BE DONE EASILY AT A LOW COST IN A SHORTER PERIOD OF TIME IN A DRILLING MACHINE. DRILLING CAN BE CALLED AS THE OPERATION OF PRODUCING A CYLINDRICAL HOLE OF REQUIRED DIAMETER AND DEPTH BY REMOVING METAL BY THE ROTATING EDGES OF A DRILL. THE CUTTING TOOL KNOWN AS DRILL IS FITTED INTO THE SPINDLE OF THE DRILLING MACHINE. A MARK OF INDENTATION IS MADE AT THE REQUIRED LOCATION WITH A CENTER PUNCH. THE ROTATING DRILL IS PRESSED AT THE LOCATION AND IS FED INTO THE WORK. THE HOLE CAN BE MADE UP TO A REQUIRED DEPTH.  GROOVING GROOVING IS THE PROCESS OF CUTTING A NARROW GROOVE ON THE CYLINDRICAL

CAVITATION ITS EFFECTS AND PRECAUTION Cavitation: Cavitation is defined the phenomenon of formation of vapour bubbles of a flowing liquid in a region where the pressure of the liquid falls below its vapour pressure and sudden collapsing of these vapour bubbles in a region of higher pressure . When the vapour bubbles collapse, a very high pressure is created. The metallic surfaces, above which these vapour bubbles collapse, is subjected to these high pressures, which cause pitting action on the surface. Thus cavities are formed on the metallic surface and also considerable noise and vibrations are produced. Effects:-      1.       The metallic surfaces are damaged and cavities are formed on the surfaces.      2.       Due to sudden collapse of vapour bubble, considerable noise and vibrations are produced.      3.       The efficiency of a turbine decreases due to cavitation. Precaution:-     1.   The pressure of the flowing liquid in any part of the hydraulic sys

CONSTRUCTION OF PELTON TURBINE  Introduction The Pelton wheel turbine is a pure impulse turbine in which a jet of fluid leaving the nozzle strikes the buckets fixed to the periphery of a rotating wheel. The energy available at the inlet of the turbine is only kinetic energy. The pressure at the inlet and outlet of the turbine is atmospheric. The turbine is used for high heads ranging from (150-2000) m. The turbine is named after L. A. Pelton, an American engineer. Parts of the Pelton turbine:- Nozzle and flow control arrangement: The water from the reservoir flows through the penstocks at the outlet of which a nozzle is fitted. The nozzle converts the total head at the inlet of the nozzle into kinetic energy. The amount of water striking the curved buckets of the runner is controlled by providing a spear in the nozzle. The spear is a conical needle which is operated either by a hand wheel or automatically in an axial direction depending upon the size of the unit. Pi

DIFFERENTIATE BETWEEN CAPSTAN AND TURRET LATHE TURRET LATHE CAPSTAN LATHE 1. Turret tool head is directly fitted on the saddle and both of them appear like one unit. 1. Turret head is mounted on a slide called ram which is mounted on the saddle 2. Saddle is moved to provide feed to the tool. 2. To provide feed to the tool, saddle is locked at a particular point and the ram is moved. 3. It is difficult to move the saddle for feed. 3. It is easy to move the ram for feed. 4. As the saddle can be moved along the entire length of the bed, it is suitable for longer workpieces. 4. As the movement of the ram is limited, it is suitable for machining shorter workpieces only. 5. To index the turret tool head, a clamping lever is released and the turret is rotated manually. 5. When the handwheel for the ram is reversed, the turret tool head is indexed automatically. 6. Limit dogs are

APRON MECHANISM IN LATHE Apron Mechanism: Apron is attached to the carriage and hangs over the front side of the lathe bed. It is useful in providing power and hand feed to both carriage and cross-slide. It is also used to provide power feed to the carriage during thread cutting through two half nuts. The construction of apron is shown in Fig. Fig - Apron Mechanism Construction Power is transmitted from the spindle to the lead screw and feed rod through the spindle gear and tumbler gear arrangement. A worm is mounted on the feed rod by a sliding key. The worm meshes with a worm gear on whose axis another gear G1 is attached. Gear G1 is attached to a small gear G2 by a bracket as shown in the diagram. Gear G4 is positioned to be in mesh with the rack gear always. Another gear G3 is mounted on the same axis of gear G4. The carriage hand wheel meant for longitudinal feed is attached to the gear G5 on the same axis. The gears G3 and G5 are always in mesh. The gear G

WHITWORTH QUICK RETURN MECHANISM FOR SHAPER MACHINE Click here for the picture The above diagram shows the mechanism as used on the apparatus. Link 1 on the top diagram is extended to point A. Attached to point A is another link with a pivot. The other end of this link terminates in a slider. In a machine tool where this mechanism is used the cutting tool is attached to this slider. The link POA rotates about O. The mechanism is driven by crank PC which rotates about C with constant velocity. The slider at P slides along POA as the crank is turned. Its path is shown by the dashed circle, centered on C and through P. Clearly when P is at P1 the slider S is at the outer extremity of its travel. When P is at P2 the slider S is at the inner extremity of its travel. Now as PC rotates with constant velocity the time taken to go from P1 to P2 is less than that taken to go from P2 to P1. However during both those time intervals the slider S is moving the same distance. Ther

BLOCK DIAGRAM OF A HORIZONTAL MILLING MACHINE AND ITS VARIOUS PARTS PARTS OF HORIZONTAL MILLING MACHINE :- 1. Base : It gives support and rigidity to the machine and also acts as a reservoir for the cutting fluids. Picture - Horizontal Milling machine 2. Column : The column is the main supporting frame mounted vertically on the base. The column is box shaped, heavily ribbed inside and houses all the driving mechanisms for the spindle and table feed. 3. Knee : The knee is a rigid casting mounted on the front face of the column. The knee moves vertically along the guide ways and this movement enables to adjust the distance between the cutter and the job mounted on the table. The adjustment is obtained manually or automatically by operating the elevating screw provided below the knee. 4. Saddle : The saddle rests on the knee and constitutes the intermediate part between the knee and the table. The saddle moves transversely, i.e., crosswise (in or out) o