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Monday, 25 November 2013

Internal Grinders

Internal Grinders Points : Internal Grinders, Chucking Internal Grinders, Planetary-Spindle grinder, Center-less ‘Internal’ Grinder, External Center-less Grinders, These machines are used chiefly for finishing round holes. On most makes, the work revolves, and hole of any size (within the limits of the machine), straight or tapered, may be finished in such parts as gears, bushings, cutters, gauges, etc. in general, small wheels are used. Diameters of 25.4 or 50.8 mm (1 or 2 in.) are common; although on rare occasions pencil wheels as small as 3.18 or 1.59 mm (1/8 in. or 1/16 in.) in diameter may be used. Frequent truing is customary for maintaining the accuracy of ordinary wheels; in fact, many internal grinders have automatic mechanisms that true the with mechanism comes into action just before the final finishing strokes of the wheel an internal grinder. There are three general types of internal grinders: 1. Chucking Internal Grinders In this machine the work to be ground is held in a chuck or fixture mounted the face plate or end of the work head spindle. Motions of wheel and work in internal grinding. 2. Planetary-Spindle grinder In which the wheel spindle not only rotates but revolves about an axis and thus maintains contact between the wheel and work. 3. Center-less ‘Internal’ Grinder This type of internal grinding eliminates the use of chucks for holding the work. Their operation requires that a preliminary operation of grinding the outside diameter be performed before the internal grinding. This outer diameter rotates on rolls and is driven, by a pressure roll. Naturally the roundness of the internal grind depends entirely on the roundness of the outer diameter. 4. External Center-less Grinders The center-less grinder, as its name implies, does not make use of center points in this, type of grinding, there is no need for locating and drilling center holes in the work piece. In other words it is not necessary to support the work between centers in center-less grinding as it is rotated against the grinding wheel. Instead, the workpiece is positioned on a work-rest blade and is fed automatically between a regulating or feed wheel which causes it to rotate, and the grinding wheel which does the cutting. The machine elements of centerless grinding machine are the grinding wheel, regulating or feed wheel, and work-rest blade. All three of these are necessary to support the work-piece in the grinding position.

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