Formulae for Face Milling
Cutting Speed(vc)

*Divide by 1000 to change to m from mm.
DC(mm);Cutter Diameter
π(3.14):Pi
n(min-1):Main Axis Spindle Speed
vc(m/min):Cutting Speed
(Problem)
What is the cutting speed when main axis spindle speed is 350min-1 and the cutter diameter is ø125 ?
(Answer)
Substitute π=3.14, DC=125, n=350 into the formula.
vc=(π•DC•n)÷1000=(3.14×125×350)÷1000
=137.4m/min
The cutting speed is 137.4m/min.
Feed Per Tooth(fz)
vf(mm/min):
Table Feed per Min.
z:Insert Number
n(min-1):
Main Axis Spindle Speed (Feed per Revolution f=zxfz)
fz(mm/t.):Feed per Tooth
(Problem)
What is the feed per tooth when the main axis spindle speed is 500min-1, number of insert is 10, and table feed is 500mm/min?
(Answer)
Substitute the above figures into the formula.
fz=Vf÷(z×n)=500÷(10×500)=0.1mm/t.
The answer is 0.1mm/t.
Table Feed(vf)
vf(mm/min):
Table Feed per Min.
z:Insert Number
n(min-1):
Main Axis Spindle Speed
fz(mm/t.):Feed per Tooth
(Problem)
What is the table feed when feed per tooth is 0.1mm/t., number of insert is 10, and main axis spindle speed is 500min-1?
(Answer)
Substitute the above figures into the formula.
vf=fz×z×n=0.1×10×500=500mm/min
The table feed is 500mm/min.
Cutting Time(Tc)
L(mm):Total Table Feed Length (Workpiece Length: (l)+Cutter Diameter:DC))
vf(mm/min):Table Feed per Min.
Tc(min):Cutting Time
(Problem)
What is the cutting time required for finishing 100mm width and 300mm length surface of a cast iron (JIS FC200) block when the cutter diameter is ø200mm, the number of inserts is 16, the cutting speed is
125m/min, and feed per tooth is 0.25mm. (spindle speed is 200min-1)
(Answer)
Calculate table feed per min
vf=0.25×16×200=800mm/min
Calculate total table feed length.
L=300+200=500mm
Substitute the above answers into the formula.
Tc=500÷800=0.625(min)
0.625×60=37.5(sec). The answer is 37.5 sec.