Calculation formula of turning
 
◆.Power required（Ne）
Power required Cutting force Cutting speed
Feed per revolution Cutting depth (Machine tool efficiency coefficient)
(Example) Machine soft steel under cutting condition that cutting depth of 3mm, cutting speed of 120m/min, feed of 0.2mm/rev, calculate the required power.(Coefficient of machine tool efficiency is 80%)(Answer) According to the table below, integrate the cutting force of cutting soft steel Ks=3100N/mm2 in the formula, to get
 
●. Ks value
Material of work-piece Tensile strength or hardness Specific cutting force of various feed
0.1(mm/rev) 0.2(mm/rev)
 0.3(mm/rev)
 0.4(mm/rev)
 0.5(mm/rev)

Soft steel		 520 3610 3100 2720 2500 2280
中硬钢 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
Cr-Mn steel 770 3830 3250 2900 2650 2400
Cr-Mn steel 630 4510 3900 3240 2900 2630
Cr-Mo steel 730 4500 3900 3400 3150 2850
Cr-Mo steel 600 3610 3200 2880 2700 2500
Cr-Ni-Mo steel 900 3070 2650 2350 2200 1980
Cr-Ni-Mo steel HB352 3310 2900 2580 2400 2200
Cr-Ni-Mo steel HRC46 3190 2800 2600 2450 2270
Inoculated castiron 360 2300 1930 1730 1600 1450
Gray cast iron HB200 2110 1800 1600 1400 1330
◆. Cutting speed（VC） ◆. Feed（f）
Cutting speed
Circumference ratioRotation speed of spindle
(Example) Rotation speed of spindle is 700min-1, diameter of work-piece isφ50. Calculate cutting speed. (Answer) Integrate π=3.14, Dm=50, n=700 in the formula,

From this, we get cutting speed is 110m/min.
Feed per revolutionCutting length per minute
Rotation speed of spindle
(Example) Rotation speed of spindle is 500 min-1, cutting length per minute is 120mm/min, calculate feed per revolution.
(Answer) Integrate n=500, I=120 in the formula,

From this, we get feed per revolution is 0.24mm/rev. .
◆. Cutting time（Tc）
◆.Theoretical surface finish（h）
Cutting time
Work-piece length
Cutting length per minute
(Example) a work piece of 100 mm long, the rotation speed of spindle is 1000 min-1, feed is 0.2mm/rev, calculate cutting time. First, calculate cutting speed per minute according to feed and rotation speed of spindle. (Answer) Integrate in the formula：

surface finish
Feed per rotation
Arc radius of cutter point
(Example) arc radius of cutter point is 0.8 mm，feed is 0.2mm/rev,calculate
theoretical surface roughness.
(Answer) integrate f=0.2mm/rev,R＝0.8 in the formula,

Theoretical surface roughness is 6μm.