The Foundation of Stable Precision：Key Insights into Concentric Grinding and Control

In high-precision machining, controlling only the dimensions within specified tolerances may still result in poor fits, wobbling, or unwanted noise. These issues often stem from neglecting concentricity, rather than simple dimensional errors.

Why Concentricity Matters

Concentricity is a geometric characteristic that defines whether circular features share the same axis. For rotating components, mating parts, or dynamically balanced parts, axis misalignment can cause：

• Uneven friction, noise, or vibration
• Assembly misfit or binding
• Reduced product lifespan and inconsistent performance

Machining Strategies for Concentricity Control

1. Single-setup machining for critical surfaces

Perform all circular feature operations under the same reference to minimize accumulated errors.

2. Process optimization and minimizing re-clamping

Every repositioning or flipping of the part can introduce reference drift. For ±0.002 mm tolerances, carefully plan the sequence and design of fixtures.

3. Post-heat-treatment finishing

For materials like SUS420, rough machine before heat treatment, then apply grinding or coordinate-based finishing to achieve precise holes and mating surfaces while compensating for thermal distortion.

4. Employ concentricity measurement equipment

Use roundness testers, profilometers, or 3D CMMs to inspect concentricity instead of relying solely on visual checks or basic measurement tools.

Practical Case Study

In a high-precision rotating component project, we controlled the concentricity between the inner bore and outer diameter within 0.003 mm by implementing：

• Rough machining with reserved allowance for heat treatment

• Post-heat-treatment precision grinding and coordinate-based machining
• Verification of dynamic balance and assembly tests
• Successful mass production with consistently stable precision

Engineering Recommendations & Key Reminders

• Dimension control alone is insufficient; geometric relationships must also be addressed
• Process design must integrate heat treatment, fixture design, and measurement methods
• Concentricity control is an engineering mindset as important as tool operation

Precision comes from every decision made, not just every tool used.