BIZOMAT MAKEOS · Maintenance
Shaft Angular Offset
What angular misalignment does this offset across a known span represent?
Convert a relative offset change measured across a known axial span into an angular misalignment.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Relative offset change across the span | mm | Actual change in relative offset between the two measurement planes. For a rim reading, use half the total indicator reading. |
| Axial span between measurement planes | mm | Axial distance between the two measurement planes. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Relative offset change across the span
- What it is
- How much the relative offset between the two shaft centrelines changes from one measurement plane to the other, for example the change in alignment-tool readings across a coupling.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0 mm to 1000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.15 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Angular misalignment rises in proportion to the offset change for small angles.
- Get it right
- For a rim dial indicator, the real offset is half the total indicator reading; entering the full reading doubles the angle.
What this means: Axial span between measurement planes
- What it is
- The axial distance along the shaft between the two planes where the offsets were measured.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.1 mm to 100000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 100 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A longer span for the same offset change means a smaller angle.
- Get it right
- Measure between the actual indicator or sensor positions, not the coupling hub length or the bearing centres.
Method and formulas
- Angle = arctan(offset change / span).
- Slope (mm per 100 mm) = 100 × offset change / span.
- Example: 0.15 mm across 100 mm gives 0.15 mm per 100 mm, 1.499999 mrad or 0.085944°.
Limitations
- Offset (parallel) misalignment, soft foot and thermal growth between cold and running conditions are not included.
- Acceptable misalignment comes from the coupling and machine manufacturers; none is applied here.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Express alignment readings as an angle or slope
- Compare readings with a coupling maker’s tolerance
- Check a shim calculation
Who it is for
- Maintenance engineers
- Design engineers
What you get
- Angular misalignment (degrees and mrad)
- Slope (mm per 100 mm)
Interpreting the result
- Alignment tolerances are often given as a slope (mm per 100 mm) for angularity and a distance for offset.
References
- Piotrowski J., Shaft Alignment Handbook, 3rd edition (CRC Press, 2006). Topic reference; no source tables or tolerances are reproduced.
Learn the Concepts Behind This Tool
These BIZOMAT Library readings explain the method this tool uses, with worked examples.
Method explained here · BIZOMAT original book
What misalignment is and what it costs
In Shaft Alignment by the Numbers
What it covers: How to describe shaft misalignment as offset and angularity in two planes, convert between the units in use, and understand what misalignment does to couplings, bearings and seals.
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