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Formulas for Cutting Power

¨ Cutting power in turning (Pc)

Input the values ap (mm) f (mm/rev) vc (m/min) Kc (MPa) η Pc (kw) ap (mm) : Depth of cut f (mm/rev) : Feed per revolution vc (m/min) : Cutting speed Kc (MPa) : Specific cutting force η : Machine coefficient Pc (kw) : Actual cutting power

(Example) What is cutting power required for machining mild steel at cutting speed 120m/min with depth of cut 3mm and feed 0.2mm/rev (When the machine coefficient is 80%)?

(Answer) Substitute the specific cutting force Kc=3100MPa into the formula. Pc=(3×0.2×120×3100)÷(60×103×0.8)=4.65(kw)

· Values of Kc Workpiece Material Tensile strength (MPa) and hardness Specific cutting force Kc(MPa) 0.1 (mm/rev) 0.2 (mm/rev) 0.3 (mm/rev) 0.4 (mm/rev) 0.6 (mm/rev) Mild steel 520 3610 3100 2720 2500 2280 Medium steel 620 3080 2700 2570 2450 2300 Hard steel 720 4050 3600 3250 2950 2640 Tool steel 670 3040 2800 2630 2500 2400 Tool steel 770 3150 2850 2620 2450 2340 Chrome manganese steel 770 3830 3250 2900 2650 2400 Chrome manganese steel 630 4510 3900 3240 2900 2630 Chrome molybdenum steel 730 4500 3900 3400 3150 2850 Chrome molybdenum steel 600 3610 3200 2880 2700 2500 Nickel chrome molybdenum steel 900 3070 2650 2350 2200 1980 Nickel chrome molybdenum steel 352HB 3310 2900 2580 2400 2200 Hard cast iron 46HRC 3190 2800 2600 2450 2270 Meehanite cast iron   360 2300 1930 1730 1600 1450 Gray cast iron 200HB 2110 1800 1600 1400 1330

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¨ Cutting power in milling (Pc)

Input the values ap (mm) ae (mm) vf (mm/min) Kc (MPa) η Pc (kw) ap (mm) : Depth of cut ae (mm) : Cutting width vf (mm/min) : Table feed per minute Kc (MPa) : Specific cutting force η : Machine coefficient Pc (kw) : Actual cutting power

(Example) What is the cutting power required for milling tool steel at cutting speed 80m/min.With depth of cut 2mm,cutting width 80mm,and table feed 280mm/min by ø250cutter with 12 insert. Machine coefficient of 80%.

(Answer) First calculate the spindle speed in order to obtain feed per tooth. n=1000vc÷p D1=(1000×80)÷(3.14×250)=101.91min-1 Feed per tooth; fz=vf÷(z×n)=280÷(12×101.9)=0.228mm/tooth Substitute specific cutting force into the formula Pc=(2×80×280×1800)÷(60×106×0.8)=1.68kw

¨Values of Kc Workpiece material Tensile strength (MPa) and hardness Specific cutting force Kc(MPa) 0.1 (mm/tooth) 0.2 (mm/tooth) 0.3 (mm/tooth) 0.4 (mm/tooth) 0.6 (mm/tooth) Mild steel 520 2200 1950 1820 1700 1580 Medium steel 620 1980 1800 1730 1600 1570 Hard steel 720 2520 2200 2040 1850 1740 Tool steel 670 1980 1800 1730 1700 1600 Tool steel 770 2030 1800 1750 1700 1580 Chrome manganese steel 770 2300 2000 1880 1750 1660 Chrome manganese steel 630 2750 2300 2060 1800 1780 Chrome molybdenum steel 730 2540 2250 2140 2000 1800 Chrome molybdenum steel 600 2180 2000 1860 1800 1670 Nickel chrome molybdenum steel 940 2000 1800 1680 1600 1500 Nickel chrome molybdenum steel 352HB 2100 1900 1760 1700 1530 Cast iron 520 2800 2500 2320 2200 2040 Hard cast iron 46HRC 3000 2700 2500 2400 2200 Meehanite cast iron 360 2180 2000 1750 1600 1470 Gray cast iron 200HB 1750 1400 1240 1050 970 Brass 500 1150 950 800 700 630 Light alloy (Al-Mg) 160 580 480 400 350 320 Light allow (Al-Si) 200 700 600 490 450 390