MACHINING Copyright Goodheart-Willcox Co., Inc. Chapter 26 Milling Machines 455 Material Type of cutter Aluminum Brass Cast iron Free cutting steel Alloy steel End mill 0.009 (0.22) 0.022 (0.55) 0.007 (0.18) 0.015 (0.38) 0.004 (0.10) 0.009 (0.22) 0.005 (0.13) 0.010 (0.25) 0.003 (0.08) 0.007 (0.18) Face mill 0.016 (0.40) 0.040 (1.02) 0.012 (0.30) 0.030 (0.75) 0.007 (0.18) 0.018 (0.45) 0.008 (0.20) 0.020 (0.50) 0.005 (0.13) 0.012 (0.30) Shell end mill 0.012 (0.30) 0.030 (0.75) 0.010 (0.25) 0.022 (0.55) 0.005 (0.13) 0.013 (0.33) 0.007 (0.18) 0.015 (0.38) 0.004 (0.10) 0.009 (0.22) Slab mill 0.008 (0.20) 0.017 (0.43) 0.006 (0.15) 0.012 (0.30) 0.003 (0.08) 0.007 (0.18) 0.004 (0.10) 0.008 (0.20) 0.001 (0.03) 0.004 (0.10) Side cutter 0.010 (0.25) 0.020 (0.50) 0.008 (0.20) 0.016 (0.40) 0.004 (0.10) 0.010 (0.25) 0.005 (0.13) 0.011 (0.28) 0.003 (0.08) 0.007 (0.18) Saw 0.006 (0.15) 0.010 (0.25) 0.004 (0.10) 0.007 (0.18) 0.001 (0.03) 0.003 (0.08) 0.003 (0.08) 0.005 (0.13) 0.001 (0.03) 0.003 (0.08) US Customary value expressed in inches per tooth. Metric value (shown in parentheses) expressed in millimeters per tooth. Increase or decrease feed until the desired surface finish is obtained. Feeds may be increased 100 percent or more depending upon the rigidity of the machine and the power available, if carbide-tipped cutters are used. Goodheart-Willcox Publisher Figure 26-30. Recommended feed rates in inches per tooth and millimeters per tooth for high-speed steel (HSS) milling cutters. Rules for determining speed and feed Having Rule Formula To find Speed of cutter in feet per minute (fpm) Diameter of cutter and revolutions per minute Diameter of cutter (in inches) multiplied by 3.1416 (π) multiplied by revolutions per minute, divided by 12 fpm = πD × rpm 12 Speed of cutter in meters per minute Diameter of cutter and revolutions per minute Diameter of cutter multiplied by 3.1416 (π) multiplied by revolutions per minute, divided by 1000 mpm = D(mm) × π × rpm 1000 Revolutions per minute (rpm) Feet per minute and diameter of cutter Feet per minute, multiplied by 12, divided by circumference of cutter (πD) rpm = fpm × 12 πD Revolutions per minute (rpm) Meters per minute and diameter of cutter in millimeters (mm) Meters per minute multiplied by 1000, divided by the circumference of cutter (πD) rpm = mpm × 1000 πD Feed per revolution (FR) Feed per minute and revolutions per minute Feed per minute, divided by revolutions per minute FR = F rpm Feed per tooth per revolution (ftr) Feed per minute and number of teeth in cutter Feed per minute (in inches or millimeters) divided by number of teeth in cutter × revolutions per minute ftr = F T × rpm Feed per minute (F) Feed per tooth per revolution, number of teeth in cutter, and rpm Feed per tooth per revolution multiplied by number of teeth in cutter, multiplied by revolutions per minute F = ftr × T × rpm Feed per minute (F) Feed per revolution and revolutions per minute Feed per revolution multiplied by revolutions per minute F = FR × rpm Number of teeth per minute (TM) Number of teeth in cutter and revolutions per minute Number of teeth in cutter multiplied by revolutions per minute TM = T × rpm rpm = Revolutions per minute T = Teeth in cutter D = Diameter of cutter π = 3.1416 (pi) π fpm = Speed of cutter in feet per minute TM = Teeth per minute F = Feed per minute FR = Feed per revolution ftr = Feed per tooth per revolution mpm = Speed of cutter in meters per minute Goodheart-Willcox Publisher Figure 26-31. Rules for determining cutting speed and feed.