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# FORMULAE FOR DRILLING

CUTTING SPEED (vc) *Unit transformation (from "mm" to "m")
vc (m/min)
Cutting Speed
D1 (mm)
Drill Diameter
π (3.14)
Pi
n (min-1)
Rotational Speed of the Main Spindle
Input the values
n (min-1)
D1(mm)
vc (m/min) (Problem)
What is the cutting speed when main axis spindle speed is 1350min-1 and drill diameter is 12mm ?
(Answer)
Substitute π =3.14, D1=12,n=1350 into the formulae
vc =(π ×D1×n)÷1000 =(3.14×12×1350)÷1000=50.9m/min
The cutting speed is 50.9m/min.

FEED OF THE MAIN SPINDLE (vf) vf(mm/min)
Feed Speed of the Main Spindle(Z axis)
f (mm/rev)
Feed per Revolution
n (min-1)
Rotational Speed of the Main Spindle
Input the values
f (mm/rev)
n(min-1)
vf (mm/min) (Problem)
What is the spindle feed (vf) when feed per revolution is 0.2mm/rev and main axis spindle speed is 1350min-1?
(Answer)
Substitute f=0.2, n=1350 into the formulae
vf = f×n = 0.2×1350 = 270mm/min
The spindle feed is 270mm/min

DRILLING TIME (Tc) Tc (min)
Drilling Time
n (min-1)
Spindle Speed
ld (mm)
Hole Depth
f (mm/rev)
Feed per Revolution
i
Number of Holes
Input the values
ld (mm)
i
n (min-1)
fr (mm/rev)

Tc (min)
second (s) (Problem)
What is the drilling time required for drilling a 30mm length hole in alloy steel at a cutting speed of 50m/min and feed 0.15mm/rev ?
(Answer)
Spindle Speed
n=(50×1000)÷(15×3.14)=1061.57min-1
Tc=(30×1)÷(1061.57×0.15)=0.188
=0.188×60=11.3sec. TOP BACK