There is no single correct cutting speed for “steel” or “aluminium”. Vc belongs to a specific combination of work material, tool and process conditions.
Start with the tool maker
The first source should be the cutter, drill or insert maker's catalogue or selection tool. The value must match material group and hardness, carbide or HSS grade, geometry, coating and operation. A generic internet table does not know those details.
What changes the recommended Vc
- material grade, hardness and surface condition,
- cutting material, geometry and coating,
- continuous or interrupted milling, drilling or turning,
- coolant strategy and delivery,
- overhang, runout, workholding and holder rigidity,
- radial engagement ae and axial depth ap.
Choose a controlled starting point
If the maker gives a range, begin toward its conservative side for a new setup or long overhang. Then inspect wear, temperature, chip shape, sound and finish. Change one factor at a time so that the source of an improvement remains visible.
Vc and fz are not interchangeable. Cutting speed strongly affects temperature and wear; chip load changes mechanical edge loading.
Only then convert Vc into RPM
Metric
n = Vc × 1000 / (π × D)If the machine limits RPM, calculate the cutting speed that will actually run. Record that value with the trial result.