# Face Milling Formulas

This page introduces formulas for calculating basic parameters necessary for face milling. The figures obtained from the calculation are for reference only. The conditions for machining depend on the machine tool you are using. Use the optimal conditions according to your actual machining circumstances.

## Cutting Speed (vc)

• π (3.14): Circular constant
• DC (mm): Cutter diameter
• n (min-1): Spindle speed
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This formula is used to calculate the cutting speed from the spindle speed and the outer diameter of the cutter.
Example:
Cutter diameter (DC) = 100 mm
Spindle speed (n) = 400 min-1
In this case, the cutting speed (vc) is approximately 125.6 m/min.

## Feed per Tooth (f)

• vf (mm/min): Table feed per minute
• z: Number of teeth
• n (min-1): Spindle speed (Feed rate fr = zxfz)
memo

This formula is used to calculate the feed per tooth from the table feed per minute (feed rate), the number of teeth, and the spindle speed.
Example:
Table feed per minute (vf) = 450 mm/min
Number of teeth (z) = 10
Spindle speed (n) = 600 min-1
In this case, the feed per tooth (f) is 0.075 mm/t.

## Table Feed (Vf)

• fz (mm/tooth): Feed per tooth
• z: Number of teeth
• n (min-1): Spindle speed (Feed rate fr = zxfz)
memo

This formula is used to calculate the table feed per minute (feed rate) from the feed per tooth, the number of teeth, and the spindle speed.
Example:
Feed per tooth (fz) = 0.2 mm/tooth
Number of teeth (z) = 8
Spindle speed (n) = 600 min-1
In this case, the table feed rate is 960 mm/min.

## Machining Time (Tc)

• L (mm): Total table feed length (Length of material (l) + Face mill diameter (DC))
• vf (mm/min): Table feed per minute
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This formula is used to calculate the machining time from the total table feed length and the table feed per minute (feed rate).
Example of finishing a block of FC200 cast iron to have a flat surface of:
Width = 150 m
Length = 250 mm
Face milling conditions used:
Feed per tooth (fz) = 0.35 mm
Number of teeth (z) = 12
Spindle speed (n) = 200 min-1
Cutting speed (vc) = 120 m/min
Face mill diameter (D1) = 220 mm
In this case,
the table feed per minute (vf) and the total table feed length (L) are:
vf = 0.35 × 12 × 200 = 840 mm/min
L = 350 + 220 = 570 mm
Substitute these values into the formula:
Tc = L ÷ vf
= 570 ÷ 1120
= 0.679 (min) × 60
= 40.74 (sec)
The machining time (Tc) is approximately 40.74 seconds.

## Net Power (Pc)

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This formula is used to calculate the net power required for face milling based on the depth and width of cut, the table feed per minute, the specific cutting force, and the machine efficiency. Example of calculating the net power required to cut tool steel with:
Depth of cut (ap) = 5 mm
Width of cut (ae) = 70 mm
Table feed per minute (vf) = 300 mm/min
Other conditions:
Specific cutting force (Kc) = 1800 MPa
Machine efficiency (η) = 80% (0.8)
Cutting speed (vc) = 80 m/min
Cutter diameter (DC) = 250 mm
Number of teeth (z) = 16
In this case, first you calculate the spindle speed (n) and then the feed per tooth of the cutter (fz).
Spindle speed (n) = 1000・vc ÷ π・D
= (1000 × 80) ÷ (3.14 × 250)
= 101.91 min-1
Feed per tooth (fz) = vf ÷ (Z × n)
= 300 ÷ (16 × 101.91)
= 0.184 mm/tooth
Substitute the above into the formula:
Pc = (5 × 70 × 300 × 1800) ÷ (60 × 106× 0.8)
= 3.937 kw
The net power required for face milling (Pc) is approximately 3.94 kW.

## Kc Values

Workpiece material Tensile strength (MPa) and stiffness Specific cutting force Kc (MPa) for each feed
0.1 (mm/tooth) 0.2 (mm/tooth) 0.3 (mm/tooth) 0.4 (mm/tooth) 0.6 (mm/tooth)
Mild steel (SS400, S10C, etc.) 520 2200 1950 1820 1700 1580
Medium steel (S45C, S50C, etc.) 620 1980 1800 1730 1600 1570
Hard steel (S55C, S58C, etc.) 720 2520 2200 2040 1850 1740
Tool steel (Carbon tool steel (SK), etc.) 670 1980 1800 1730 1700 1600
Tool steel (Alloy tool steel (SKS), etc.) 770 2030 1800 1750 1700 1580
Chrome-manganese steel (Manganese carbide (MnC), etc.) 770 2300 2000 1880 1750 1660
Chrome-manganese steel (Manganese carbide (MnC), etc.) 630 2750 2300 2060 1800 1780
Chrome molybdenum steel (SCM grades, etc.) 730 2540 2250 2140 2000 1800
Chrome molybdenum steel (SCM grades, etc.) 600 2180 2000 1860 1800 1670
Nickel chrome molybdenum steel (SNCM415, etc.) 940 2000 1800 1680 1600 1500
Nickel chrome molybdenum steel (SNCM439, etc.) 352HB 2100 1900 1760 1700 1530
Austenitic stainless steel (SUS304, etc.) 155HB 2030 1970 1900 1770 1710
Cast steel (SCC, etc.) 520 2800 2500 2320 2200 2040
Hard cast iron 46HRC 3000 2700 2500 2400 2200
Meehanite cast iron (FC350, etc.) 360 2180 2000 1750 1600 1470
Gray cast iron (FC250, etc.) 200HB 1750 1400 1240 1050 970
Brass (C3710, etc.) 500 1150 950 800 700 630
Light alloy (Al-Mg, A5005, etc.) 160 580 480 400 350 320
Light alloy (Al-Si, A4032, etc.) 200 700 600 490 450 390
Light alloy (Al-Zn-Mg-Cu, A7075, etc.) 570 880 840 840 810 720

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