Drilling machine cutting speed calculations
 
A lathe operator must be able to calculate the rpm of the lathe spindle according to the material to be cut and the diameter of the material or drill. Below is a table with recommended cutting speed in m/min for different materials,

To calculate the cutting speed we will use the following formula:

V = π x D x N

Were

  • V = cutting speed

  • π = 3.141

  • D = diameter of work or drill

  • N = rotational frequency of spindle in revolutions per minute (RPM)

Turning and boring cutting speed table

Example 1

An aluminium workpiece has to be drilled with a 30 mm drill bit. The cutting speed for aluminium is 50 m/min. Calculate the spindle speed (N) in revolutions per minute

Answer

V = π x D x N

N = V/π x D

N = 50/ π.03

N = 530.51 RPM

 

The spindle will be set to the speed closes to the speed above
 

Example 2

Calculate the spindle speed in revolutions per minute for drilling an 8mm diameter hole on an Aluminium plate.
 

The cutting speed for Aluminium is 50m/min.

Answer

V = π x D x N

N = V/π x D

N = 50/ π.008

N = 1989,43 RPM