FORMULAS FOR MILLING
CUTTING SPEED (vc)
- vc (SFM)
- :Cutting Speed
- D1 (inch)
- :Cutter Diameter
- π (3.14)
- :Pi
- n (min-1)
- :Main Axis Spindle Speed
(Problem) :
What is the cutting speed when main axis spindle speed is 350min-1 and cutter diameter is Ø5" ?
(Answer):
Substitute π3.14, D=5", n=350 into the formulae.
vc =π×D×n÷12=3.14×5"×350÷12= 457.9SFM
The cutting speed is 457.9SFM.
FEED PER TOOTH (fz)
- fz (IPT)
- :Feed per Tooth
- z
- :Insert Number
- vf(inch/min)
- :Table Feed per Min.
- n (min-1)
- :Main Axis Spindle Speed (Feed per Revolution fr=z x fz)
(Problem) :
What is the feed per tooth when the main axis spindle speed is 500min-1, insert number is 10, and table feed is 20inch/min ?
(Answer):
Substitute the above figures into the formulae.
fz =Vf÷(z×n)=20÷(10×500) = .004IPT
The answer is .004IPT.
TABLE FEED (vf)
- vf(inch/min)
- :Table Feed per Min.
- fz (IPT)
- :Feed per Tooth
- n (min-1)
- :Main Axis Spindle Speed
- z
- :Insert Number
(Problem) :
What is the table feed when feed per tooth is .004IPT, insert number is 10, and main axis spindle speed is 500min-1?
(Answer):
Substitute the above figures into the formulae.
vf = fz×z×n = .004IPT×10×500 = 20inch/min
The table feed is 20inch/min.
CUTTING TIME (Tc)
- Tc (min)
- :Cutting Time
- vf(inch/min)
- :Table Feed per Min.
- L (inch)
- :Total Table Feed Length (Workpiece Length(l)+Cutter Diameter(D1)
(Problem) :
What is the cutting time required for finishing 4" width and 12" length surface of a cast iron (GG20) block when cutter diameter is Ø4", the number of inserts is 16, the cutting speed is 410SFM , and feed per tooth is .01. (spindle speed is 200min-1)
(Answer):
Calculate table feed per min vf=.01×16×200=32inch/min
Calculate total table feed length. L=12+4=16inch
Substitute the above answers into the formulae.
Tc =16÷32= 0.5(min)
The answer is 30 sec.
CUTTING SPEED (vc)
* Divide by 1,000 to change to m from mm.
- vc (m/min)
- Cutting Speed
- D1 (mm)
- Cutter Diameter
- π (3.14)
- Pi
- n(min-1)
- Main Axis Spindle Speed
(Problem)
What is the cutting speed when main axis spindle speed is 350min
-1 and cutter diameter isø125? (Answer)
Substitute π=3.14, D
1=125, n=350 into the formulae.
vc=(π×D1×n)÷1000=(3.14×125×350)÷1000 =137.4(m/min)
The cutting speed is 137.4 m/min.
FEED PER TOOTH (fz)
- fz (mm/tooth)
- Feed perTtooth
- z
- Insert Number
- vf (mm/min)
- Table Feed per Min.
- n (min-1)
- Main Axis Spindle Speed (Feed per Revolution f = z x fz)
(Problem)
What is the feed per tooth when the main axis spindle speed is 500min
-1, insert number is 10, and table feed is 500mm/min?
(Answer)
Substitute the above figures into the formulae.
fz=vf÷(z×n)=500÷(10×500)=0.1mm/tooth
The answer is 0.1mm/tooth.
TABLE FEED (vf)
- vf (mm/min)
- Table Feed per Min.
- z
- Insert Number
- fz (mm/tooth)
- Feed per Tooth
- n (min-1)
- Main Axis Spindle Speed
(Problem)
What is the table feed when feed per tooth is 0.1mm/tooth, insert number is 10, and main axis spindle speed is 500min
-1?
(Answer)
Substitute the above figures into the formulae.
vf=fz×z×n=0.1×10×500=500mm/min
The table feed is 500 mm/min.
CUTTING TIME (Tc)
- Tc(min)
- Cutting Time
- vf(mm/min)
- Table Feed per Min.
- L (mm)
- Total Table Feed Length (Workpiece Length: l+Cutter Diameter: D1)
(Problem)
What is the cutting time required for finishing 100 mm width and 300 length surface of a cast iron (GG20) block when cutter diameter is ø200, the number of inserts is 16, the cutting speed is 125m/min, and feed per tooth is 0.25 mm. (spindle speed is 200 min
-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 formulae.
Tc=500÷800=0.625(min)
0.625×60=37.5(sec). The answer is 37.5 sec.