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Rim & Face Shaft Alignment Calculator

Enter dial indicator readings to calculate misalignment and foot corrections for pump-to-motor alignment.

Fire Pump & Generator Spares

Rim & Face Shaft Alignment Report

Printed: 03 Jun 2026 19:00

Settings
Which machine moves?
Shim and foot corrections are calculated for the moveable machine only. In most pump installations the motor/engine is bolted down first and the pump is shimmed to suit — but sometimes it's the other way around.
Coupling type
Sets the pass/fail tolerance. Flexible jaw couplings are most forgiving; rigid couplings require the tightest alignment. If unsure, use Flexible jaw as a safe starting point.
Rim Readings (parallel offset)
Rim readings — parallel offset
The gauge bracket is mounted on one shaft and the plunger bears on the rim (outside diameter) of the other coupling half. As you rotate the shaft, the reading changes if the shafts are not on the same centreline — this is called parallel (or radial) offset.

Zero the gauge at 12 o'clock (top). Record the reading at each 90° position, including sign. Bottom is usually negative when the shaft dips.

Mount gauge on fixed machine shaft, bear on rim of moveable coupling half. Zero at top (12 o'clock). Record readings with sign at each position.

Top (0°)
Left (270°)
Right (90°)
Bottom (180°)

ⓘ Rim sum check: Top + Bottom and Left + Right should each equal zero (±10% acceptable for sag).

Face Readings (angularity)
Face readings — angularity
Move the gauge plunger to bear on the face (end) of the coupling half. Rotating the shaft now shows if the shaft centrelines meet at an angle rather than running parallel — this is angular misalignment.

Zero at top. The sweep radius (distance from shaft centre to gauge contact point) is needed to convert face readings into an angle — measure it and enter it in Machine Dimensions below.

Move gauge plunger to bear on the coupling face. Zero at top. Record readings with sign at each position.

Top (0°)
Left (270°)
Right (90°)
Bottom (180°)
Machine Dimensions (for shim calc)

Enter distances on the moveable machine. Leave blank to skip shim calculation.

Coupling to front feet (dimension A)
Measure along the shaft centreline from the coupling face (where the gauge is mounted) to the nearest set of hold-down bolts/feet on the moveable machine.

This distance determines how much the angular misalignment affects the front foot correction.
Front to rear feet (dimension B)
Measure between the front and rear sets of hold-down bolts on the moveable machine (not the total machine length).

A longer wheelbase means angular misalignment has less effect per foot — the shim amounts spread out over a greater distance.
Face gauge sweep radius
The distance from the shaft centreline to the point where the gauge plunger touches the coupling face.

Measure it on the coupling half — it is typically half the coupling outside diameter. A larger radius gives a more sensitive (and more accurate) angular reading for the same misalignment angle.
Enter readings on the left to see results
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