Table 15d. Face Milling Speed Adjustment Factors for Feed, Depth of Cut, and Lead Angle Cutting Speed V = V opt 3 F f 3 F d 3 F ar
Ratio of the two cutting speeds ( average / optimum ) given in the tables V avg / V opt
Depth of Cut, inch (mm), and Lead Angle
Ratio of Radial Depth of Cut/Cutter Diameter, ar / D
Ratio of
1 in
0.4 in
0.2 in
0.1 in
0.04 in (1.0 mm)
Chosen Feed to Optimum Feed
(25.4 mm)
(10.2 mm) 15 ° 45 °
(5.1 mm)
(2.4 mm) 15 ° 45 °
1.00 1.10 1.25 1.35 1.50 1.75 2.00 15 ° 45 °
15 °
45 °
15 °
45 °
1.00 0.75 0.50 0.40 0.30 0.20 0.10
Feed Factor, F f
Depth of Cut Factor, F d
Radial Depth of Cut Factor, F ar
1.00 1.0 1.0 1.0 1.0 1.0 1.0 1.0 0.78 1.11 0.94 1.16 0.90 1.10 1.00 1.29 1.47 1.66 0.72 1.00 1.53 1.89 2.43 3.32 5.09 0.90 1.00 1.02 1.05 1.07 1.09 1.10 1.12 0.78 1.10 0.94 1.16 0.90 1.09 1.00 1.27 1.45 1.58 0.73 1.00 1.50 1.84 2.24 3.16 4.69 0.80 1.00 1.03 1.09 1.10 1.15 1.20 1.25 0.80 1.10 0.94 1.14 0.91 1.08 1.00 1.25 1.40 1.52 0.75 1.00 1.45 1.73 2.15 2.79 3.89 0.70 1.00 1.05 1.13 1.22 1.22 1.32 1.43 0.81 1.09 0.95 1.14 0.91 1.08 1.00 1.24 1.39 1.50 0.75 1.00 1.44 1.72 2.12 2.73 3.77 0.60 1.00 1.08 1.20 1.25 1.35 1.50 1.66 0.81 1.09 0.95 1.13 0.92 1.08 1.00 1.23 1.38 1.48 0.76 1.00 1.42 1.68 2.05 2.61 3.52 0.50 1.00 1.10 1.25 1.35 1.50 1.75 2.00 0.81 1.09 0.95 1.13 0.92 1.08 1.00 1.23 1.37 1.47 0.76 1.00 1.41 1.66 2.02 2.54 3.39 0.40 1.00 1.09 1.28 1.44 1.66 2.03 2.43 0.82 1.08 0.95 1.12 0.92 1.07 1.00 1.21 1.34 1.43 0.78 1.00 1.37 1.60 1.90 2.34 2.99 0.30 1.00 1.06 1.32 1.52 1.85 2.42 3.05 0.84 1.07 0.96 1.11 0.93 1.06 1.00 1.18 1.30 1.37 0.80 1.00 1.32 1.51 1.76 2.10 2.52 0.20 1.00 1.00 1.34 1.60 2.07 2.96 4.03 0.86 1.06 0.96 1.09 0.94 1.05 1.00 1.15 1.24 1.29 0.82 1.00 1.26 1.40 1.58 1.79 1.98 0.10 1.00 0.80 1.20 1.55 2.24 3.74 5.84 0.90 1.04 0.97 1.06 0.96 1.04 1.00 1.10 1.15 1.18 0.87 1.00 1.16 1.24 1.31 1.37 1.32 For HSS (high-speed steel) tool speeds in the first speed column, use Table 15a to determine appropriate feeds and depths of cut. Tabular speeds and feeds data for face milling in Table 11 through Table 14 are based on a 10-tooth, 8-inch diameter face mill, operating with a 15-degree lead angle, 3 ∕ 64 -inch cutter insert nose radius, axial depth of cut = 0.1 inch, and radial depth (width) of cut = 6 inches (i.e., width of cut to cutter diameter ratio = 3 ∕ 4 ). For other depths of cut (radial or axial), lead angles, or feed, calculate the ratio of desired (new) feed to optimum feed (largest of the two feeds given in the speed table), and the ratio of the two cutting speeds ( V avg / V opt ). Use these ratios to find the feed factor F f at the intersection of the feed ratio row and the speed ratio column in the left third of the table. The depth of cut factor F d is found in the same row as the feed factor, in the center third of the table, in the column corresponding to the depth of cut and lead angle. The radial depth of cut factor F ar is found in the same row as the feed factor, in the right third of the table, in the column corresponding to the radial depth of cut to cutter diameter ratio ar / D . The adjusted cutting speed can be calculated from V = V opt 3 F f 3 F d 3 F ar , where V opt is the smaller ( optimum ) of the two speeds from the speed table (from the left side of the column containing the two feed/speed pairs). The cutting speeds as calculated above are valid if the cutter axis is centered above or close to the center line of the workpiece (eccentricity is small). For larger eccentricity (i.e., the cutter axis is offset from the center line of the workpiece by about one-half the cutter diameter or more), use the adjustment factors from Table 15b and Table 15c (end and side milling) instead of the factors from this table. Use Table 15e to adjust end and face milling speeds for increased tool life up to 180 minutes. Slit and Slot Milling: Tabular speeds are valid for all tool diameters and widths. Adjustments to the given speeds for other feeds and depths of cut depend on the circumstances of the cut. Case 1: If the cutter is fed directly into the workpiece, i.e., the feed is perpendicular to the surface of the workpiece, as in cutting off, then this table (face milling) is used to adjust speeds for other feeds. The depth of cut factor is not used for slit milling ( F d = 1.0), so the adjusted cutting speed V = V opt 3 F f 3 F ar . For determining the factor F ar , the radial depth of cut ar is the length of cut created by the portion of the cutter engaged in the work. Case 2: If the cutter is fed parallel to the surface of the workpiece, as in slotting, then Table 15b and Table 15c are used to adjust the given speeds for other feeds. See Fig. 5.
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