Machinery's Handbook, 31st Edition
USING THE SPEEDS AND FEEDS TABLES 1093 Tool life is the most important factor in a machining system, so speeds and feeds cannot be selected as simple numbers, but must be considered with respect to the many parameters that influence tool life. The accuracy of the combined feed/speed data presented is believed to be very high. However, machining is a variable and complicated process and use of the speeds and feeds tables requires the user to follow the instructions carefully to achieve good predictability. The results achieved, therefore, may vary due to material condition, tool material, machine setup, and other factors, and cannot be guaranteed. The feed values given in the tables are valid for the standard tool geometries and fixed depths of cut that are identified in the table footnotes. If the cutting parameters and tool geometry established in the table footnotes are maintained, turning operations using either the optimum or average feed/speed data (Table 1 through Table 9) should achieve a constant tool life of approximately 15 minutes; tool life for milling, drilling, reaming, and threading data (Table 10 through Table 14 and Table 17 through Table 22) should be approximately 45 minutes. The reason for the different economic tool lives is the higher tooling cost associated with milling-drilling operations than for turning. If the cutting parameters or tool geometry are different from those established in the table footnotes, the same tool life (15 or 45 minutes) still may be maintained by applying the appropriate speed adjustment factors, or tool life may be increased or decreased using tool life adjustment factors. The use of the speed and tool life adjustment factors is described in the examples that follow. Both the optimum and average feed/speed data given are reasonable values for effective cutting. However, the optimum set with its higher feed and lower speed (always the left entry in each table cell) will usually achieve greater productivity. In Table 1, for example, the two entries for turning 1212 free-machining plain carbon steel with uncoated carbide are 17 ∕ 805 and 8 ∕ 1075. These values indicate that a feed of 0.017 in/rev and a speed of 805 ft/min, or a feed of 0.008 in/rev and a speed of 1075 ft/min can be used for this mate- rial. The tool life, in each case, will be approximately 15 minutes. If one of these speed and feed pairs is assigned an arbitrary cutting time of 1 minute, then the relative cutting time of the second pair to the first is equal to the ratio of their respective feed 3 speed products. Here, the same amount of material that can be cut in 1 minute, at the higher feed and lower speed (17 ∕ 805), will require 1.6 minutes at the lower feed and higher speed (8 ∕ 1075) be- cause 17 3 805/(8 3 1075) = 1.6 minutes. 1000
Tool Life, T (min)
100
T = 5
T = 15 T = 45 T = 120
10
0.01
0.1
1
Equivalent Chip Thickness, ECT (mm)
Cutting Speed versus Equivalent Chip Thickness with Tool Life as a Parameter
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