Answers to common questions about CNC feed and speed calculations, units, formulas, materials and calculator limitations.
Using the calculators
The calculators are designed to make the arithmetic visible. Enter the values you know, confirm the unit system and read the result with its unit. If the result looks surprising, check the units before changing the machining condition.
A calculator cannot inspect your tool, machine or workholding. The output is therefore a starting calculation, not a guarantee.
Units and conversions
Metric and imperial formulas use different conversion factors. Do not mix metres per minute with inches or SFM with millimetres. Convert first or use the calculator mode that matches the data in your tooling reference.
Materials and tooling
Material family alone does not determine a safe feed or speed. Grade, hardness, cutter geometry, coating, engagement and machine rigidity all matter. Use the actual toolmaker recommendation wherever available.
Frequently asked questions
Are results guaranteed?
No. They are mathematical starting calculations.
Why can two charts give different values?
They may assume different tools, materials, coatings, engagement or machine conditions.
Should I use the automatic calculator for production?
Use it as a starting estimate and verify it against the actual toolmaker and machine data.