Machinery's Handbook, 31st Edition
1310
DIAMOND WHEELS Table 5. General Diamond Wheel Recommendations for Wheel Type and Abrasive Specification Typical Applications or Operation Basic Wheel Type Abrasive Specification
Table 5. (Continued) General Diamond Wheel Recommendations for Wheel Type
Cylindrical or Centertype Grinding
D1A1 D1A1
MD120-P100-B 1 ∕ 8 MD150-N100-B 1 ∕ 8 MD150-R100-B 1 ∕ 4 MD400-L50-B 1 ∕ 16
Internal Grinding Slotting and Cutoff
D1A1R
Lapping
Disc
MD220-B 1 ∕ 16
Rough: Finish:
Hand Honing
DH1, DH2
MD320-B 1 ∕ 6 General recommendations for the dry grinding, with resin bond diamond wheels, of most grades of cemented carbides of average surface to ordinary finishes at normal rates of metal removal with average size wheels, as published by Cincinnati Milacron, are listed in Table 5. A further set of variables are the dimensions of the wheel, which must be adapted to the available grinding machine and, in some cases, to the configuration of the work. The general abrasive specifications in Table 5 may be modified to suit operating condi tions by the following suggestions: Use softer wheel grades for harder grades of carbides, for grinding larger areas or larger or wider wheel faces. Use harder wheel grades for softer grades of carbides, for grinding smaller areas, for using smaller and narrower face wheels and for light cuts. Use fine grit sizes for harder grades of carbides and to obtain better finishes. Use coarser grit sizes for softer grades of carbides and for roughing cuts. Use higher diamond concentration for harder grades of carbides, for larger diameter or wider face wheels, for heavier cuts, and for obtaining better finish. Guidelines for the Handling and Operation of Diamond Wheels.— Grinding ma- chines used for grinding with diamond wheels should be of the precision type, in good service condition, with true running spindles and smooth slide movements. Mounting of Diamond Wheels: Wheel mounts should be used which permit the precise centering of the wheel, resulting in a runout of less than 0.001 inch (0.0254 mm) axially and 0.0005 inch (0.0127 mm) radially. These conditions should be checked with a 0.0001-inch (0.001 mm) type dial indicator. Once mounted and centered, the diamond wheel should be retained on its mount and stored in that condition when temporarily removed from the machine. Truing and Dressing: Resinoid bonded diamond wheels seldom require dressing, but when necessary a soft silicon carbide stick may be hand-held against the wheel. Peripheral and cup type wheels may be sharpened by grinding the cutting face with a 60 to 80 grit silicon carbide wheel. This can be done with the diamond wheel mounted on the spindle of the machine, and with the silicon carbide wheel driven at a relatively slow speed by a specially designed table-mounted grinder or by a small table-mounted tool post grinder. The diamond wheel can be mounted on a special arbor and ground on a lathe with a tool post grinder; peripheral wheels can be ground on a cylindrical grinder or with a special brake-controlled truing device with the wheel mounted on the machine on which it is used. Cup and face type wheels are often lapped on a cast iron or glass plate using a 100 grit silicon carbide abrasive. Care must be used to lap the face parallel to the back, otherwise they must be ground to restore parallelism. Peripheral diamond wheels can be trued and dressed by grinding a silicon carbide block or a special diamond impregnated bronze block in a manner similar to surface grinding. Conventional diamonds must not be used for truing and dressing diamond wheels. Speeds and Feeds in Diamond Grinding.— General recommendations are as follows: Wheel Speeds: The generally recommended wheel speeds for diamond grinding are in the range of 5000 to 6000 surface feet per minute (1525–1830 m/min), with this upper limit as a maximum to avoid harmful “overspeeding.” Exceptions from that general rule are diamond wheels with coarse grains and high concentration (100 percent) where the wheel wear in dry surface grinding can be reduced by lowering the speed to 2500– 3000 sfpm (760–915 m/min). However, this lower speed range can cause rapid wheel breakdown in finer grit wheels or in those with reduced diamond concentration.
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