Center Bore: Component Specs, Materials & Applications

Q: What is the difference between a clearance fit and an interference fit for a center bore?

A clearance fit (e.g., H7/g6) allows easy assembly and disassembly, suitable for applications requiring frequent maintenance. An interference fit (e.g., H7/s6) creates a tight bond through shaft expansion or bore contraction, providing superior torque transmission and eliminating the need for additional fasteners, but requires precise thermal or hydraulic assembly methods.

Q: How does center bore quality affect rotor balance?

Poor concentricity or surface imperfections in the center bore can cause the rotor's mass center to deviate from its geometric center, leading to dynamic imbalance. This imbalance increases vibration, bearing wear, noise, and reduces operational efficiency and lifespan. Precision machining and verification are critical.

Component Specifications

Definition

The center bore is a critical cylindrical feature machined into the geometric center of a rotor disk. Its primary function is to provide an accurate mounting interface with the drive shaft, ensuring concentricity, minimizing radial runout, and transmitting torque efficiently. It is typically characterized by tight dimensional tolerances, specific surface finishes, and may include keyways, splines, or interference fit specifications to secure the disk to the shaft.

Working Principle

The center bore operates on the principle of precise geometric interfacing. It aligns the rotor disk concentrically with the rotational axis of the shaft. This alignment minimizes dynamic imbalance, reduces vibration, and ensures efficient power transmission. The fit between the bore and shaft (e.g., clearance, transition, or interference) determines the method of torque transmission and axial location.

Materials

Typically matches the rotor disk base material. Common specifications include: AISI 4140 alloy steel (hardened and tempered), ASTM A36 steel, aluminum alloys (e.g., 6061-T6, 7075), or titanium alloys (e.g., Ti-6Al-4V). Material selection depends on required strength, weight, corrosion resistance, and operating temperature.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Bore Diameter	Tolerance: Typically H7 or tighter (e.g., ±0.013 mm)
Concentricity	< 0.025 mm TIR relative to rotor OD
Surface Finish	Ra 1.6 μm or better for precision fits
Perpendicularity	< 0.05 mm relative to mounting face
Keyway Dimensions	If applicable, per ANSI B17.1 or ISO 773

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

ISO 286-1, ISO 1101, DIN 7184, ANSI B4.1

Parent Products

This component is used in the following industrial products

Rotor Disk

A rotating disk that holds turbine blades and transmits mechanical energy in turbines and expanders.

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Engineering Analysis

Risks & Mitigation

Misalignment leading to excessive vibration
Improper fit causing slippage or fatigue failure
Concentricity error inducing dynamic imbalance
Corrosion at the bore-shaft interface

FMEA Triads

Trigger: Inaccurate machining or tool wear during bore drilling/reaming.
Failure: Excessive bore diameter or poor surface finish resulting in loose fit, slippage, and loss of torque transmission.
Mitigation: Implement statistical process control (SPC) for machining, use certified tooling, and perform 100% inspection of critical bore dimensions with air gauges or CMMs.

Trigger: Thermal expansion mismatch between rotor and shaft materials.
Failure: Seizure (if interference fit becomes excessive) or loss of fit (if clearance becomes too large) during operation, leading to catastrophic failure.
Mitigation: Calculate and specify fits based on operational temperature ranges and material coefficients of thermal expansion. Consider material pairing and operational environment.

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Geometric tolerances per ISO 1101:2017. Dimensional tolerances per ISO 286-1:2010 for fits. Balance grades per ISO 1940-1.

Test Method

Dimensional: Coordinate Measuring Machine (CMM) or precision bore gauges. Concentricity: Dial indicators or laser alignment tools. Surface Finish: Profilometer. Fit Verification: Go/No-Go gauges or functional test with shaft.

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

Verify equipment lists, process limits, capacity, and representative production evidence.

Inspection readiness

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

Check the legal entity, factory address, ownership, certifications, and direct contacts.

CNFX does not score or rank suppliers. Buyers must verify all claims and documents with the legal manufacturer before ordering.

Manufacturers of Center Bore

1 company lists this product among what they make. Company figures are quoted from each company's own website; every card states where the relationship came from.

Tengzhou Borui CNC Machine Co., Ltd.

Tengzhou, Shandong, CN

Founded 2015

Also makes: CNC Lathe, Precision CNC Machining Center, Gantry Machining Center and 5 more

Listed on the company's own website · profile compiled by CNFX from public sources

Listed there as: “drilling machining center bore”
View source page ↗ boruimc.com · checked 2026-08-26

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Manufacturer listings support early research and capability understanding. They are not certification, ranking, or transaction guarantees.

Compiled and source-reviewed by the CNFX editorial team. Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review

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Frequently Asked Questions

What is the difference between a clearance fit and an interference fit for a center bore?