Machinery's Handbook, 31st Edition
726 Surface Plates of specialized applications, and have engineering staffs that will design a surface plate to meet those needs. However, most applications and manufacturers’ products fall under the design guidelines of the tables in the GGG-P-463c Federal Specification. Table 2a. Standard Sizes for Rectangular Granite Surface Plates GGG-P-463c Inch Metric
Width (inch)
Length (inch)
Calculated Diagonal (inch)
Area (ft 2 ) 1.5 2.25 1
Width (mm)
Length (mm)
Calculated Diagonal (mm)
Area (m 2 ) 0.090 0.135 0.202 0.270 0.360 0.540 0.720 0.810 1.080 1.350 1.620 1.440 1.800 2.160 2.880 3.600 4.500 4.320
12 18 18 24 24 36 48 36 48 60 72 48 60 72 96
17.0 21.6 25.5 30.0 33.9 43.3 53.7 50.9 60.0 70.0 80.5 67.9
300 350 450 600
424 541 636 750
12
300
18
450
3 4 6 8 9
600 900 1200 900 1200 1500 1800 1200 1500 1800 2400 3000 300 2400 3600
849 1082 1342 1273 1500 1749 2012 1697 1921 2163 2683 3231 3304 3000 4025
24
600
12 15 18 16 20 24 32 40 50 48 72
36
900
76.9 86.5 107.3 129.2 134.2 120.0 161.0
48
1200
120 120 96 144
60 72
1500 1800
6.480 Table 2b. Standard Sizes for Round Granite Surface Plates GGG-P-463c Inch Millimeter Diameter (inch) Area (ft 2 ) Diameter (mm) Area (m 2 ) 12 0.8 300 0.071 18 1.8 450 0.159 24 3.1 600 0.283 36 7.1 900 0.636 48 48 1200 1.131 Thickness : For rectangular and round surface plates, specify thickness only if essential; see Appendix 30 and inch and metric versions of Tables XI and XII of GGG-P-463c. Surface plate grades are established in the Federal Specifications and are the guidelines by which the plates are calibrated. The flatness tolerances in microinches for standard inch-dimension plates, listed in Table 3a ., are obtained through the standard formula: D 40 25 Total flatness tolerance for inch dimension grade AA plates in. 2 µ − = + where D = diagonal or diameter of the plate in inches. The calculated flatness tolerance for grade AA is rounded to the nearest 25 µ in. For metric plate sizes, the total flatness tolerance of grade AA plates in micrometers is: . D 1 162 10 Total flatnesstolerance for metric grade AA plates m 2 6 µ = + – where D = diagonal or diameter of the plate in millimeters. For both the inch and metric plates, the tolerances of the A and B grades are 2 and 4 times, respectively, those for grade AA. Table 3a and Table 3b , adapted from Federal Specification GGG-P-463c, contain the calculated tolerances for the standard size and grades of rectangular and round surface plates.
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