Table 15c. End, Slit, and Side Milling Speed Adjustment Factors for Radial Depth of Cut
Cutting Speed, V = V opt 3 F f 3 F d
Ratio of Radial
V avg / V opt
V avg / V opt
Maximum Feed/Tooth Factor
Minimum Feed/Tooth Factor
1.25
1.50
2.00
2.50
3.00
4.00
1.25
1.50
2.00
2.50
3.00
4.00
Depth of Cut to Diameter
Feed Factor F f at Maximum Feed per Tooth, F f 1
Feed Factor F f at Minimum Feed per Tooth, F f 2
1.00 0.75 0.60 0.50 0.40 0.30 0.20 0.10 0.05 0.02
1.00 1.00 1.00 1.00 1.10 1.35 1.50 2.05 2.90 4.50
1.00 1.15 1.23 1.25 1.25 1.20 1.14 0.92 0.68 0.38
1.00 1.24 1.40 1.50 1.55 1.57 1.56 1.39 1.12 0.71
1.00 1.46 1.73 2.00 2.17 2.28 2.57 2.68 2.50 1.93
1.00 1.54 2.04 2.50 2.83 3.05 3.78 4.46 4.66 4.19
1.00 1.66 2.34 3.00 3.51 3.86 5.19 6.77 7.75 7.90
1.00 1.87 2.89 4.00 4.94 5.62 8.56
0.70 0.70 0.70 0.70 0.77 0.88 1.05 1.44 2.00 3.10
1.18 1.24 1.24 1.20 1.25 1.23 1.40 0.92 0.68 0.38
1.30 1.48 1.56 1.58 1.55 1.57 1.56 1.29 1.12 0.70
1.50 1.93 2.23 2.44 2.55 2.64 2.68 2.50 2.08 1.38
1.69 2.38 2.95 3.42 3.72 4.06 4.43 4.66 4.36 3.37
1.85 2.81 3.71 4.51 5.08 5.76 6.37 7.76 8.00 7.01
2.15 3.68 5.32 6.96 8.30
10.00 11.80 17.40 20.80
13.10 17.30 21.50
22.20 This table is for side milling, end milling when the radial depth of cut (width of cut) is less than the tool diameter (i.e., less than full slot milling), and slit milling when the feed is parallel to the work surface (slotting). The radial depth of cut to diameter ratio is used to determine the recommended maximum and minimum values of feed/tooth, which are found by multiplying the feed/tooth factor from the appropriate column above (maximum or minimum) by feed opt from the speed tables. For example, given two feed/speed pairs 7 ∕ 15 and 4 ∕ 45 for end milling cast, medium-carbon, alloy steel, and a radial depth of cut to diameter ratio ar / D of 0.10 (a 0.05-inch width of cut for a 1 ∕ 2 -inch diameter end mill, for example), the maximum feed f max = 2.05 3 0.007 = 0.014 in/tooth and the minimum feed f min = 1.44 3 0.007 = 0.010 in/tooth. The feed selected should fall in the range between f min and f max . The feed factor F d is determined by interpolating between the feed factors F f 1 and F f 2 corresponding to the maximum and minimum feed per tooth, at the appropriate ar / D and speed ratio. In the example given, ar / D = 0.10 and V avg / V opt = 45 ∕ 15 = 3, so the feed factor F f 1 at the maximum feed per tooth is 6.77, and the feed factor F f 2 at the minimum feed per tooth is 7.76. If a working feed of 0.012 in/tooth is chosen, the feed factor F f is half way between 6.77 and 7.76 or by formula, F f = F f 2 + (feed − f min )/( f max − f min ) 3 ( F f 1 − F f 2 ) = 7.76 + (0.012 − 0.010)/ (0.014 − 0.010) 3 (6.77 − 7.76) = 7.27. The cutting speed is V = V opt 3 F f 3 F d , where F d is the depth of cut and lead angle factor from Table 15b that corresponds to the feed ratio (chosen feed)/ f max , not the ratio (chosen feed)/ optimum feed. For a feed ratio = 0.012 ∕ 0.014 = 0.86 (chosen feed/ f max ), depth of cut = 0.2 inch and lead angle = 45 ° , the depth of cut factor F d in Table 15b is between 0.72 and 0.74. Therefore, the final cutting speed for this example is V = V opt 3 F f 3 F d = 15 3 7.27 3 0.73 = 80 ft/min. Slit and Side Milling: This table only applies when feed is parallel to the work surface, as in slotting. If feed is perpendicular to the work surface, as in cutting off, obtain the required speed-correction factor from Table 15d (face milling). The minimum and maximum feeds/tooth for slit and side milling are determined in the manner described above, however, the axial depth of cut factor F d is not required. The adjusted cutting speed, valid for cutters of any thickness (width), is given by V = V opt 3 F f . Examples are given in the text.
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