ISO 21940-11 Balance Tolerance Calculator
Permissible residual unbalance from the balance quality grade, rotor mass and service speed, divided across the correction planes.
Calculators & Tools
Free engineering calculators for balancing work. Each one runs in your browser and explains the math behind the result.
Unbalance Plane Translator
Move a two-plane unbalance reading to new correction planes while keeping the static and couple unbalance the same.
Vector Calculator
Add or subtract two unbalance vectors, with the result in polar and rectangular form.
Vector Expression Calculator
Evaluate expressions across any number of unbalance vectors, including trial-weight corrections and influence coefficients.
Process Capability (Cpk) Calculator
Process capability against an unbalance tolerance, from the mean and standard deviation of residual unbalance readings.
Engineering Unit Conversion Calculator
Convert unbalance, length, weight, velocity, acceleration, density and other units used in balancing and measurement.
Technical Library
Technical papers written by BTI engineers on the theory and practice of balancing: what unbalance is, how to specify it, and what happens when the geometry is unhelpful.
Basics of Balancing: Static, Couple and Dynamic Unbalance
The four foundational terms, the three types of unbalance with their formulas, units, and why force rises with the square of speed.
Balancing Theory: Inertia, Centrifugal Force and Unbalance Types
Mass moment of inertia, couples and bearing reactions, metric versus imperial formulations, and the four unbalance types including quasi-static.
Specifying Unbalance and Where to Put the Tolerance Planes
Why tolerance planes belong at the bearings, and what the same number permits when they are moved inboard.
Balancing with an Offset Mass Center
Three cases of bearing reaction, including when single-plane correction leaves the assembly worse than before.
Axle Balancing: Guidelines and Fundamental Considerations
Where axle unbalance originates, three ways to write the specification, single-plane correction strategy, end weight and clutched assemblies.
The Benefits of Automated Armature Balancing
Angular error arithmetic, correction by feel, and why tightening armature tolerances outrun a manual process.
Unbalance Tolerance in Vector Space
Unbalance has direction as well as magnitude, so its tolerance is an area. Four specification styles and the zone each describes.
Gaging Symbols
GD&T Symbols: The 14 Geometric Tolerancing Controls
All fourteen controls by category, and how datum errors become unbalance on a balancing machine.
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