Tools & Materials Required
Safety Notes
- Support the shaft adequately before attempting alignment -- a dropped shaft can cause serious injury
- Never tighten one side of a housing fully before the other -- alternate sides to prevent cocking
- Use calibrated torque values for foundation bolts as per housing manufacturer's specification
1. Base Plate Preparation
A bearing housing is only as good as the surface it sits on. Before placing the housing, the mounting surface must be clean, flat, and level.
2. Soft Foot Check & Correction
Soft foot occurs when one or more housing feet do not sit flat on the base. Tightening the bolts forces the housing to distort, transmitting stress to the bearing and causing premature failure.
Do not torque -- just enough to prevent movement.
Zero the indicator.
If the housing lifts more than 0.05 mm, soft foot is present at that location.
Shim thickness = indicator reading. Re-tighten and re-check until movement is below 0.05 mm at all four feet.
3. Shaft Alignment with Dial Indicators
For two-bearing shafts (e.g., conveyor pulley, fan), the housings must be aligned so the shaft centerline is straight and level. Misalignment causes uneven bearing loading and drastically reduces life.
Reverse Indicator Method
- Mount dial indicators on each shaft coupling half (or on temporary brackets clamped to the shaft at each bearing position).
- Rotate both shafts together in 90-degree increments (0, 90, 180, 270 degrees).
- Record vertical and horizontal offset and angularity at each position.
- Calculate shim corrections for each housing foot: the vertical offset tells you how much to raise/lower, the angularity tells you the difference between front and back feet.
4. Final Torque & Run-In Test
Tighten in 3 stages (30%, 60%, 100% of final torque) in a diagonal sequence to distribute clamping force evenly.
Tightening bolts can shift the housing. Always re-verify alignment readings after final torque and adjust if needed.
Start at no load for 10 minutes, monitoring bearing temperature. Gradually increase to 50% load for 30 minutes, then full load. Temperature should stabilize within 20 C above ambient.
Pro Tips
- 1Use stainless steel shims, not mild steel -- mild steel corrodes and compresses over time, causing alignment drift
- 2Mark the housing and base with a scribed witness line after alignment -- this helps detect housing movement during operation
- 3For long shafts (>2 meters), check for shaft sag using a precision level and compensate in your alignment calculations
Important Warnings
- Never use more than 4 shims per foot -- the stack becomes unstable. If you need more, machine the base surface
- Do not use gasket material as a shim substitute -- it compresses under load and alignment degrades over weeks
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