When installing caster bearings, how can I ensure the concentricity of the axle and bearing seat?

Caster Bearing Installation Concentricity Control Guide

 

I. Preliminary Preparation

Component Accuracy:

Axle: Diameter tolerance h6/h7, straightness ≤ 0.03mm/m (checked with a dial indicator).

Bearing seat: Inner hole tolerance H7, perpendicularity to the mounting surface ≤ 0.05mm/100mm.

Bearing: Accuracy ≥ ISO Grade 6, clearance acceptable.

Cleaning:

Remove burrs and oil from the mating surfaces of the axle and bearing seat. Ensure the gap is ≤ 0.02mm (checked with a straightedge).

When pre-installing a split bearing seat, pre-tighten the bolts to 80%, leaving room for adjustment.

 

II. Installation and Alignment

Preliminary Installation:

Fit the bearing outer ring into the seat bore (interference fit requires cold/shrunk installation). Lightly tap the axle into the inner ring (lubricant is applied for a tight fit).

Concentricity Calibration:

Dial indicator method: Measure shaft radial runout to ≤0.05mm. If out of tolerance, fine-tune the bearing seat position.

Feeler gauge method: Measure the clearance difference between the axle and the seat edge in all directions to ≤0.05mm.

Batch installation: Use concentric fixtures with a clearance of ≤0.03mm.

 

III. Accuracy Verification

Final Inspection:

Radial runout (center section) ≤0.05mm (≤0.03mm under heavy load).

Axial play ≤0.1mm.

Manual rotation should ensure no sticking or abnormal noise.

Securing Requirements:

Tighten the bolts diagonally (e.g., M8 bolts, 25-30N·m). Re-measure the runout increment to ≤0.02mm.

 

IV. Key Points

Split seat: First secure one side, then calibrate the concentricity of the other side.

Long shaft with multiple bearings: Use a spirit level/laser to calibrate the straightness of the seat at both ends.

Temperature Effects: Expansion clearance is reserved for high and low temperature environments, and concentricity is maintained at ≤0.05mm.

 

Summary
Concentricity control focuses on component accuracy, step-by-step calibration, and quantitative testing. A deviation of ≤0.05mm ensures lifespan (for heavy-duty casters, concentricity exceeding 0.1mm reduces lifespan by at least 30%).