BIZOMAT MAKEOS · Maintenance
Shaft Alignment Plan (Rim and Face Corrections with Thermal Growth)
From my rim and face readings, how many shims do I add or remove at each foot so the shafts line up when the machines are hot, and is the running alignment within tolerance as it stands?
Alignment plan for a movable machine coupled to a stationary one: offset and slope at the coupling and the corrections at the front and back feet from rim and face dial readings (as the rim and face alignment tool), the vertical thermal growth of each machine from its foot-to-centreline height and support temperature rise and the cold offset to allow (as the thermal growth for hot alignment tool), the cold shim corrections that give true alignment when hot, and the running offset and angularity if nothing is changed, against your tolerances.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Dial readings (movable machine) | ||
| Rim reading at 6 o’clock (zeroed at 12) | mm | Rim dial reading at the bottom, with the dial zeroed at the top (as the rim and face tool). |
| Face reading at 6 o’clock (zeroed at 12) | mm | Face dial reading at the bottom, zeroed at the top. |
| Diameter of the face reading circle | mm | Diameter of the circle the face indicator travels on. |
| Coupling to front foot of movable machine | mm | Distance from the coupling to the front feet of the movable machine. |
| Coupling to back foot of movable machine | mm | Distance from the coupling to the back feet. |
| Thermal growth | ||
| Stationary machine: foot to shaft centreline | mm | Height from the stationary machine’s feet to its shaft centreline. |
| Stationary machine: expansion coefficient | µm/(m·K) | Expansion coefficient of the stationary machine’s supports. |
| Stationary machine: support temperature rise | K | Rise in temperature of the stationary machine’s supports from cold to running. |
| Movable machine: foot to shaft centreline | mm | Height from the movable machine’s feet to its shaft centreline. |
| Movable machine: expansion coefficient | µm/(m·K) | Expansion coefficient of the movable machine’s supports. |
| Movable machine: support temperature rise | K | Rise in temperature of the movable machine’s supports. |
| Tolerances | ||
| Offset tolerance at the coupling | mm | Largest running offset you accept at the coupling. |
| Angularity tolerance | mm/100 mm | Largest running angularity you accept. |
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.
Dial readings (movable machine)
What this means: Rim reading at 6 o’clock (zeroed at 12)
- What it is
- The rim (radial) dial indicator reading taken on the movable machine’s side of the coupling with the dial at the bottom, after zeroing it at the top. Half of it is the vertical offset between the shafts.
- Units and format
- Enter a number in mm: millimetres. The form accepts -100 mm to 100 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.24 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The offset is half the rim reading, and it shifts the correction at both feet by the same amount.
- Get it right
- Keep the sign exactly as the dial shows it; a positive or negative reading decides whether shims are added or removed. Correct for bracket sag first if you know it.
What this means: Face reading at 6 o’clock (zeroed at 12)
- What it is
- The face (axial) dial indicator reading at the bottom of the coupling face, with the dial zeroed at the top. Divided by the face reading circle diameter, it gives the slope (angularity) between the shafts.
- Units and format
- Enter a number in mm: millimetres. The form accepts -100 mm to 100 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.05 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A larger face reading increases the slope, which adds more correction at the back feet than at the front.
- Get it right
- Read the face and rim with the same rotation and sign convention; push the shafts against the same end float stop for each reading.
What this means: Diameter of the face reading circle
- What it is
- The diameter of the circle the face indicator tip travels on as the shafts turn, measured across the coupling face through the shaft centre.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 10000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 120 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Slope is the face reading divided by this diameter, so a larger diameter means a smaller computed angle.
- Get it right
- Measure where the tip actually touches, not the coupling outside diameter; a larger circle gives larger face readings for the same angle.
What this means: Coupling to front foot of movable machine
- What it is
- The horizontal distance along the shaft from the coupling (the face reading plane) to the centre of the movable machine’s front feet, the pair nearer the coupling.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 100000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 250 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The front correction is offset plus slope times this distance.
- Get it right
- Measure to the centre of the foot bolts, along the shaft axis.
What this means: Coupling to back foot of movable machine
- What it is
- The horizontal distance along the shaft from the coupling to the centre of the movable machine’s back feet, the pair furthest from the coupling.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 100000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 650 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The back correction is offset plus slope times this distance, so the slope matters more here.
- Get it right
- Measure from the same coupling plane as the front distance; it must be the total distance, not the distance between the feet.
Thermal growth
What this means: Stationary machine: foot to shaft centreline
- What it is
- The vertical height from the underside of the stationary machine’s feet (the shim plane) to its shaft centreline. This height of support grows when the machine warms up.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 100000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 300 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Growth of the stationary machine is proportional to this height.
- Get it right
- Measure from the bottom of the feet, not from the floor or baseplate below the shims.
What this means: Stationary machine: expansion coefficient
- What it is
- The coefficient of linear thermal expansion of the stationary machine’s casing and supports between the feet and the shaft centreline, from the material data for the casing.
- Units and format
- Enter a number in µm/(m·K): micrometres per metre per kelvin. The form accepts 0.000001 µm/(m·K) to 100 µm/(m·K). Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 11 µm/(m·K) as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Growth of the stationary machine is proportional to this coefficient.
- Get it right
- The unit is micrometres per metre per kelvin, the same as ×10⁻⁶ per K; do not type it as a decimal fraction.
What this means: Stationary machine: support temperature rise
- What it is
- How much the stationary machine’s supports warm up from the cold state when you align to normal running, as the average rise through the height from feet to centreline.
- Units and format
- Enter a number in K: kelvin (a difference of 1 K equals 1 °C). The form accepts -200 K to 1000 K. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20 K as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Growth of the stationary machine is proportional to this rise.
- Get it right
- Use the temperature of the supports, not of the process fluid or bearing oil; measure it on a running machine if you can.
What this means: Movable machine: foot to shaft centreline
- What it is
- The vertical height from the underside of the movable machine’s feet (the shim plane) to its shaft centreline, the support height that grows when it warms up.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 100000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 250 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Growth of the movable machine is proportional to this height and raises the cold offset to allow.
- Get it right
- Measure from the bottom of the feet where the shims sit.
What this means: Movable machine: expansion coefficient
- What it is
- The coefficient of linear thermal expansion of the movable machine’s casing and supports, from the material data for that casing.
- Units and format
- Enter a number in µm/(m·K): micrometres per metre per kelvin. The form accepts 0.000001 µm/(m·K) to 100 µm/(m·K). Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 11 µm/(m·K) as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Growth of the movable machine is proportional to this coefficient.
- Get it right
- Cast iron, steel and aluminium casings differ; use the material of the movable machine, not the stationary one.
What this means: Movable machine: support temperature rise
- What it is
- How much the movable machine’s supports warm up from cold to normal running, as the average rise between its feet and shaft centreline.
- Units and format
- Enter a number in K: kelvin (a difference of 1 K equals 1 °C). The form accepts -200 K to 1000 K. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 60 K as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Growth of the movable machine is proportional to this rise.
- Get it right
- Motors often run warmer at the frame than at the feet; take an average over the support height.
Tolerances
What this means: Offset tolerance at the coupling
- What it is
- The largest running offset between the shaft centrelines at the coupling that you accept, from the coupling maker, the machine maker or your site alignment standard.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0 mm to 10 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.05 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- The check compares it with half the rim reading after thermal growth, which is the true centreline offset, not the dial reading.
What this means: Angularity tolerance
- What it is
- The largest angularity between the shafts you accept, expressed as the gap change over each 100 mm of diameter, from the coupling maker or your site alignment standard.
- Units and format
- Enter a number in mm/100 mm: mm/100 mm. The form accepts 0 mm/100 mm to 10 mm/100 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.05 mm/100 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Some standards give angularity per 100 mm, others per coupling diameter or as an angle; convert to millimetres per 100 mm first.
Method and formulas
- Offset = rim ÷ 2; slope = face ÷ face diameter; correction at a foot = offset + slope × distance, positive meaning add shims (as the rim and face alignment tool).
- Growth = α H ΔT for each machine; the movable machine rises by g₂ − g₁ more than the stationary one when hot (as the thermal growth tool).
- Cold correction = correction − (g₂ − g₁) at both feet; running offset if unchanged = offset − (g₂ − g₁); angularity = slope × 100.
- Example: add 0.12517 mm at the front feet and add 0.29183 mm at the back; the movable machine grows 0.099 mm more than the stationary one.
Limitations
- Vertical plane only; repeat for the horizontal plane with side readings (no thermal term unless the supports grow sideways).
- Rigid feet with no soft foot; check soft foot before shimming.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Plan shims for a pump or fan alignment
- Allow for thermal growth when aligning cold
- Decide whether a machine needs realigning
Who it is for
- Millwrights
- Maintenance fitters
- Reliability engineers
What you get
- Offset, slope and foot corrections from the readings
- Thermal growth and cold offset
- Cold shim corrections and running misalignment
Interpreting the result
- A machine that runs hotter must be set low when cold so it grows into line.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2645–2650, 375–376. Topic reference; no source tables or recommended settings 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
Making the moves
In Shaft Alignment by the Numbers
What it covers: How to combine readings and thermal growth into cold shim corrections, choose shims, make the vertical then horizontal moves against indicators, and confirm the running result.
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Open the Shaft Alignment Plan (Rim and Face Corrections with Thermal Growth) calculator