# FORMULAE FOR CUTTING POWER

CUTTING POWER in TURNING (Pc)

Pc (kW)
Actual Cutting Power
ap (mm)
Depth of Cut
f (mm/rev)
Feed per Revolution
vc (m/min)
Cutting Speed
Kc (MPa)
Specific Cutting Force
η
(Machine Coefficient)
Input the values
ap (mm)
f (mm/rev)
vc (m/min)
Kc (MPa)
h

Pc (kw)

(Problem)
What is the cutting power required for machining mild steel at cutting speed 120m/min with depth of cut 3mm and feed 0.2mm/rev (Machine coefficient 80%)?
Substitute the specific cutting force Kc=3100MPa into the formula.
Pc=(3×0.2×120×3100)÷(60×103×0.8)=4.65(kw)

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

CUTTING POWER in MILLING (Pc)

Pc (kW)
Actual Cutting Power
ap (mm)
Depth of Cut
ae (mm)
Cutting Width
vf (mm/min)
Table Feed per Min.
Kc (MPa)
Specific Cutting Force
η
(Machine Coefficient)
Input the values
ap (mm)
ae (mm)
vf (m/min)
Kc (MPa)
h

Pc (kw)

(Problem)
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 ø250 cutter with 12 insert. Machine coefficient 80%.
First, calculate spindle speed in order to obtain feed per tooth.
n=1000vc÷pD1=(1000×80)÷(3.14×250)=101.91min-1
Feed per Tooth
fz = vf÷(z×n) = 280 ÷ (12×101.9) = 0.228mm/tooth
Substitute the specific cutting force into the formulae.
Pc=(2×80×280×1800)÷(60×106×0.8)=1.68kw

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 7000 630
Light Alloy (Al-Mg) 160 580 480 400 350 320
Light Allow (Al-Si) 200 700 600 490 450 390