GRINDING FEEDS AND SPEEDS Table 2. Grindability Overview Machinery's Handbook, 31st Edition
1271
V w
Roughing Depth a r = 0.025
ECT 3 10 − 5
Finishing Depth a r = 0.0025
Material Group
V
SMRR 10
10
1 Unhardened 2 Stainless 3 Cast Iron 4 Tool Steel 5 Tool Steel 6 Tool Steel 7Tool Steel
33 33 33 33 33 33 33 33
3827 1080 4000 3190 2870 2580 1080 1045
1263 360 1320 1050
50 15 53 42 38 35 15 14
500 150 530 420 380 350 150 140
950 850 360 345
8 Heat resistant 9 Carbide with 10 Ceramics with Diamond Wheel Diamond Wheel
SMRR 600 = 50 SMRR 600 = 21
2
20
5 5
600 = 1200
V
V 84 Procedure to Determine Data.— The following wheel-life recommendations are de- signed for 4 values of ECT = 0.00017, 0.00033, 0.00050 and 0.00075 mm (shown as 17, 33, 50 and 75 in the tables). Lower values of ECT than 0.00010 mm (0.000004 in.) are not recommended as these may lie to the left of the H -curve. 600 = 411 0.84 The user selects any one of the ECT values, or interpolates between these, and selects the wheel speed for 10 or 100 minutes life, denoted by V 10 and V 100 , respectively. For other desired wheel lives the wheel speed can be calculated from the tabulated Taylor constants C and n = 0.26 as follows: (V 3 T (desired) ) 0 . 26 = C, the value of which is tabulated for each ECT value. C is the value of cutting speed V at T = 1 minute, hence is the same as for the speed V 1 . V 1 × 1 0.26 = C, thus V 1 = C V 1 = C 1 0.26 = C V 10 = C ÷ 10 0.26 = C ÷ 1.82 V 100 = C ÷ 100 0.26 = C ÷ 3.31. Example 6: A tool steel in material group 6 with ECT = 0.00033, has constant C= 4690, V 10 = 2578 m/min, and V 100 = 1417 m/min. From this information, find the wheel speed for desired wheel-life of T = 15 minutes and T = 45 minutes. For T = 15 minutes we get V 15 = 4690 ÷ 15 0.26 = 2319 m/min (7730 fpm) and for T = 45 minutes V 45 = 4690 ÷ 45 0.26 = 1743 m/min (5810 fpm). The Tables are arranged in 3 sections: 1. Speeds V 10 and V 1 = Constant CST(standard) for 4 ECT values 0.00017, 0.00033, 0.00050 and 0.00075 mm. Values C U and V 10U refer to user calibration of the standard values in each material group, explained in the following. 2. Speeds V 100 (first row of 3), V 10 and V 1 (last in row) corresponding to wheel lives 100, 10 and 1 minutes, for 4 ECT values 0.00017, 0.00033, 0.00050 and 0.00075 mm. 3. Specific metal removal rates SMRR 100 , SMRR 10 and SMRR 1 corresponding to wheel lives 100, 10 and 1 minutes, for the 4 ECT values 0.00017, 0.00033, 0.00050, and 0.00075 mm. The 2 Graphs show: wheel life versus wheel speed in double logarithmic coordinates (Taylor lines); and, SMRR versus wheel speed in double logarithmic coordinates for 4 ECT values: 0.00017, 0.00033, 0.00050 and 0.00075 mm.
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