ISO material selection
How to use the calculator
Click on the ISO group of your material (P, M, K, N, S or H), select a subgroup from the list and enter the hardness in HB units. The calculator will instantly display the starting cutting speed Vc (m/min) for carbide tools and the specific cutting force kc1.1 (N/mm²). If HB is unknown, the values are basic for the subgroup.
What do ISO groups mean?
P - Steels. The widest group: carbon, alloy, tool. Long chips, moderate kc. Vc varies from 90 to 350 m/min depending on hardness.
M - Stainless steels. Austenitic (304, 316L), martensitic (420), duplex (2205) and PH steels (17-4PH). Tendency to hardening and sticking - require a sharp edge and continuous feeding.
K - Cast iron. Gray, high strength (HF), bleached, malleable and ADI. Dust/short chips, flank abrasive wear. High strength varieties require CBN.
N - Non-ferrous metals. Wrought and cast aluminum, copper, brass, bronze, magnesium alloys. High speeds, risk of build-up is a key factor in the choice of coating and geometry.
S - Heat resistant and titanium.Ti-6Al-4V, Inconel 718, cobalt alloys. The most severe cutting conditions: low thermal conductivity, hardening, sticking. Minimum Vc, high coolant pressure.
H - Hardened > 44 HRC. Instead of grinding - hard turning CBN/PCBN. Small cutting depths, rigid clamping, no shock loads.
How does HB correction work?
Model: Vc = Vc_base × (HB_ref / HB)^0.6—classical power-law dependence (Taylor-like). The harder the material, the lower the permissible speed. The HB factor is displayed in the third cell of the results: a value < 1 means a decrease in Vc, > 1 means an increase is acceptable.
Kc (specific cutting force) is adjusted linearly based on the deviation of HB from the subgroup reference value.
Frequently Asked Questions
Why is Vc a starting value? The actual speed depends on the diameter, grade of alloy, coating, feed, cooling and rigidity of the machine. Use as a starting point, then optimize for durability.
What is kc1.1? Specific cutting force at 1 mm chip thickness, exponent 1 (ISO 3685). Used to calculate spindle power and tool load.
To select a specific alloy grade and geometry for your material, consult our technologists.