Drilling Basics: RPM and Feed in CNC Machining

Correct spindle speed and feed rate are essential for good hole quality and tool life when drilling.

1. Cutting speed and drill diameter

Most drill data is given as cutting speed V_c in m/min. The spindle speed depends on drill diameter:

rpm = (1000 × Vc) / (π × D)
    

where V_c is cutting speed in m/min and D is drill diameter in mm. You can automate this using the CNC Drill RPM & Feed Calculator.

2. Feed per revolution

Drill feed is often specified as feed per revolution f_n (mm/rev). The linear feed rate is then:

feed (mm/min) = rpm × fₙ
    

Example: 1000 rpm with f_n = 0.2 mm/rev → 200 mm/min.

3. Practical tips

• Use lower cutting speeds in tough materials and stainless steel
• Reduce feed near breakthrough to avoid burrs and chipping
• Check toolmaker catalogs for recommended V_c and f_n
• Use peck cycles for deep holes to improve chip evacuation

Use the drilling calculator to quickly test different speeds and feeds and then fine-tune at the machine.