Machinery's Handbook, 31st Edition
1316 CYLINDRICAL GRINDING Whatever method is used for holding the part on cylindrical types of grinding machines, two basic conditions must be satisfied: 1) the part should be located with respect to its cor rect axis of rotation; and 2) the work drive must cause the part to rotate, at a specific speed, around the established axis. The lengthwise location of the part, although controlled, is not too critical in traverse grinding; however, in plunge grinding, particularly when shoulder sections are also involved, it must be assured with great accuracy. Table 1 presents a listing, with brief discussions, of work-holding methods and devices that are most frequently used in cylindrical grinding. Table 1. Work-Holding Methods and Devices for Cylindrical Grinding Designation Description Discussion
Centers, nonrotating (“dead”), with drive plate
Headstock with nonrotating spindle holds the center. Around the spindle, an independently supported sleeve carries the drive plate for rotating the work. Tailstock for opposite center. Word held between two centers obtains its rotation from the concurrently applied drive by the live headstock spindle and live tailstock spindle. Two, three, or four jaws moved radially through mechanical elements, hand-, or power-operated, exert concentrically acting clamping force on the workpiece. Force applied by hand or power of a flexible diaphragm causes the attached jaws to deflect temporarily for accepting the work, which is held when force is released. Holding devices with externally or internally acting clamping force, easily adaptable to power actuation, assuring high centering accuracy. Has four independently actuated jaws, any or several of which may be used, or entirely removed, using the base plate for supporting special clamps. Flat plates, with pole distribution adapted to the work, are mounted on the spindle like chucks and may be used for work with the locating face normal to the axis. Two basic types are used: (a) the two-jaw type supporting the work from the back (back rest), leaving access by the wheel; (b) the three-jaw type (center rest). Single-purpose devices, designed for a particular workpiece, primarily for providing special locating elements.
The simplest method of holding the work between two opposite centers is also the potentially most accurate, as long as correctly prepared and located center holes are used in the work. Eliminates the drawback of the common center-type grinding with driver plate, which requires a dog attached to the workpiece. Driven spindles permit the grinding of the work up to both ends. Adaptable to workpieces of different configurations and within a generally wide capacity of the chuck. Flexible in uses that, however, do not include high-precision work. Rapid action and flexible adaptation to different work configurations by means of special jaws offer varied uses for the grinding of disk-shaped and similar parts. Limited to parts with previously machined or ground holding surfaces, because of the small range of clamping movement of the collet jaws. Used for holding bulky parts, or those of awkward shape, which are ground in small quantities not warranting special fixtures. Applicable for light cuts such as are frequent in tool making, where the rapid clamping action and easy access to both the O.D. and the exposed face are sometimes of advantage. A complementary work-holding device, used in conjunction with primary work holders, to provide additional support, particularly to long and/or slender parts. Typical workpieces requiring special fixturing are, as examples, crankshafts where the holding is combined with balancing functions; or internal gears located on the pitch circle of the teeth for O.D. grinding.
Centers, driving type
Chuck, geared, or cam-actuated
Chuck, diaphragm
Collets
Faceplate
Magnetic plate
Steady rests
Special fixtures
Selection of Grinding Wheels for Cylindrical Grinding.— For cylindrical grinding, as for grinding in general, the primary factor to be considered in wheel selection is the work material. Other factors are the amount of excess stock and its rate of removal (feeds and speeds), the desired accuracy and surface finish, the ratio of wheel and work diameter, wet or dry grinding, etc. In view of these many variables, it is not practical to set up a complete
Copyright 2020, Industrial Press, Inc.
ebooks.industrialpress.com
Made with FlippingBook - Share PDF online