Free Engineering Tool
Shim Thickness Calculator
Calculate required shim thickness at each motor foot for vertical shaft alignment correction. Uses simple geometry based on coupling gap and foot distances.
Shim Results
Shim Calculation Geometry
The shim at each foot corrects for both offset and angular misalignment:
Shimrear = Offset + (Angle × Drear / Dcoupling)
Where offset is vertical displacement at the coupling, and angle is the gap difference divided by the coupling diameter, projected to each foot distance.
Standard Shim Sizes
| Thickness (mm) | Thickness (mil/thou) | Material | Color Code |
|---|---|---|---|
| 0.05 | 2 | Stainless steel | Gold/Yellow |
| 0.10 | 4 | Stainless steel | Orange |
| 0.125 | 5 | Stainless steel | Purple |
| 0.25 | 10 | Stainless steel | Red |
| 0.50 | 20 | Stainless steel | Green |
| 0.75 | 30 | Stainless steel | Blue |
| 1.00 | 40 | Stainless steel | Silver |
| 2.00 | 80 | Stainless steel | Brown |
| 3.00 | 120 | Mild steel | — |
⚠️ Best Practice: Use no more than 3–5 shims under any one foot. Too many shims create a “spongy” base leading to soft foot. If total shim thickness exceeds 3 mm, consider machining the base or using a single precision-ground shim.
Alignment Tolerances by Speed
| RPM | Max Offset (mm) | Max Angularity (mm/100mm) |
|---|---|---|
| 600 | 0.10 | 0.10 |
| 900 | 0.07 | 0.07 |
| 1200 | 0.05 | 0.05 |
| 1500 | 0.05 | 0.05 |
| 1800 | 0.04 | 0.04 |
| 3000 | 0.03 | 0.03 |
| 3600 | 0.025 | 0.025 |
Shimming Best Practices
- Always use pre-cut stainless steel shims — never cut your own from sheet metal
- Remove any existing paint, rust, or burrs from the foot and base before shimming
- Check for soft foot before beginning alignment (tighten one bolt, measure gap at others)
- Use the minimum number of shims possible — combine to use 2–3 shims max
- Shims must be clean, flat, and the correct size for the bolt and foot
- After shimming, tighten bolts in a cross pattern to rated torque
- Re-check alignment after final tightening — shimming can shift during torquing
- Document all shim changes in the alignment report
Thermal Growth Compensation
For hot-running machines, account for thermal growth. The motor may need to be set LOW at ambient temperature so that thermal expansion brings it into alignment at operating temperature:
Δh = α × L × ΔT, where α is the coefficient of thermal expansion (~12 μm/m/°C for steel), L is the distance from base to centerline, and ΔT is the temperature rise above ambient.
The procedures described on this page were developed and field-tested by the Vibromera team using the Balanset-1A, a portable dual-channel balancer and vibration analyzer for on-site rotor balancing.
Professional shaft alignment tools and vibration analysis instruments.
Nikolai Shelkovenko
Nikolai Shelkovenko is a vibration analysis engineer and the founder and CEO of Vibromera. For more than 15 years he has balanced rotating equipment in the field rather than on a test bench: mulchers, industrial fans, crushers, centrifuges, shafts and spindles. That work is what the Balanset instruments grew out of — they were designed as a tool a specialist can carry to the machine and use alone, on site, not as laboratory equipment. Vibromera was founded in 2017 and has been based in Porto, Portugal, since 2023. Development, assembly and support of the Balanset line all happen here. The flagship instrument is the Balanset-1A, a portable analyser for single- and two-plane balancing and for vibration diagnostics. Nikolai is personally involved in customer support, in working through difficult balancing cases and in the development of the software. He works with customers worldwide, in any language.
