ISO 21940 Balance Grade Calculator
Permissible residual unbalance for a rotor from its G-grade, mass and service speed.
G-grades are speed-referenced: G2.5 means the mass-center orbits at 2.5 mm/s at service speed regardless of rotor size. A 20 kg toolholder assembly at 12,000 rpm gets only ~40 gยทmm โ about a paint fleck at the rim.
Formula
Note: Condition-monitoring guidance, not a substitute for the machine maker's limits or a qualified vibration analyst on safety-critical equipment.
Permissible residual unbalance for a rotor from its G-grade, mass and service speed. A free cnc machining: speeds, feeds & tool wear tool โ no sign-up, no upload, instant results in your browser.
About ISO 21940 Balance Grade Calculator
ISO 21940 Balance Grade Calculator computes the governing relationship e_per = G/ฯ (mm) ยท U_per = e_per ร rotor mass live as you type. G-grades are speed-referenced: G2.5 means the mass-center orbits at 2.5 mm/s at service speed regardless of rotor size. A 20 kg toolholder assembly at 12,000 rpm gets only ~40 gยทmm โ about a paint fleck at the rim. Defaults are pre-filled with realistic values for this exact scenario, and the worked example substitutes your numbers step by step so the math is never a black box.
How to use ISO 21940 Balance Grade Calculator
- 1Enter your values โ Balance grade G, Rotor mass, Max service speed (sensible defaults are pre-filled).
- 2Read the live results: Permissible unbalance, Specific unbalance e.
- 3Check the "with your numbers" line to see e_per = G/ฯ (mm) ยท U_per = e_per ร rotor mass substituted step by step.
- 4Adjust inputs until the scenario matches yours, then copy or share the result.
Why use ISO 21940 Balance Grade Calculator?
- โInstant, free and private โ every calculation runs client-side in your browser; nothing is uploaded
- โBuilt on the stated formula e_per = G/ฯ (mm) ยท U_per = e_per ร rotor mass with authoritative sources cited on the page (ISO 20816-1 (ex 10816) โ Mechanical vibration evaluation; ISO 21940-11 โ Rotor balancing; ISO 3685 โ Tool-life testing with single-point turning tools)
- โG-grades are speed-referenced: G2.5 means the mass-center orbits at 2.5 mm/s at service speed regardless of rotor size.
- โSI โ Imperial toggle converts your inputs in place, so you can work in the units your drawings use
Frequently asked questions
What formula does the iso 21940 balance grade calculator use?+
It evaluates e_per = G/ฯ (mm) ยท U_per = e_per ร rotor mass, exactly as published. Sources: ISO 20816-1 (ex 10816) โ Mechanical vibration evaluation; ISO 21940-11 โ Rotor balancing; ISO 3685 โ Tool-life testing with single-point turning tools. The substituted worked example on the page lets you verify every step against the textbook.
How should I read the result โ and how far can I trust it?+
G-grades are speed-referenced: G2.5 means the mass-center orbits at 2.5 mm/s at service speed regardless of rotor size. Condition-monitoring guidance, not a substitute for the machine maker's limits or a qualified vibration analyst on safety-critical equipment.
When is this calculator the right tool for the job?+
Permissible residual unbalance for a rotor from its G-grade, mass and service speed. A free cnc machining: speeds, feeds & tool wear tool. A 20 kg toolholder assembly at 12,000 rpm gets only ~40 gยทmm โ about a paint fleck at the rim. For neighbouring scenarios, the related tools below cover the same engine with different presets.
Does it support both metric and imperial units?+
Yes โ the SI โ Imperial toggle converts the values already in the fields, preserving the physical quantity, so you can flip mid-calculation without re-entering anything.
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