INDUSTRY COMPONENT

Central Bore

Central bore is the precision-machined axial opening in a hollow spindle that enables tool passage, coolant flow, and workpiece support in machining operations.

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Component Specifications

Definition
The central bore is a critical cylindrical aperture running concentrically along the longitudinal axis of a hollow spindle. It serves as the primary conduit for tool shanks (in live tooling applications), coolant/lubricant delivery systems, and bar stock/material feeding mechanisms. Engineered with precise dimensional tolerances and surface finishes, it maintains rotational balance, minimizes vibration transmission, and ensures alignment with machine tool axes. In CNC lathes and machining centers, it directly influences maximum bar capacity, tool clearance, and chip evacuation efficiency.
Working Principle
The central bore operates on rotational kinematics principles where its concentric alignment with spindle bearings ensures minimal radial runout during high-speed rotation. It functions as a pressure boundary for hydraulic/pneumatic systems in power chuck applications and as a waveguide for cutting fluids. The bore's diameter-to-length ratio affects torsional stiffness, while its internal geometry (straight, tapered, or threaded) determines tool interface compatibility and clamping force distribution.
Materials
Typically manufactured from case-hardened alloy steels (AISI 4140/4340), bearing steels (SAE 52100), or through-hardened tool steels with 58-62 HRC surface hardness. For corrosive environments, stainless steels (17-4PH) or ceramic-coated variants are used. Internal surfaces often receive nitriding or TiN coatings for wear resistance.
Technical Parameters
  • Max RPM Dependent on diameter (e.g., 6000 RPM for 50mm bore)
  • Straightness <0.02 mm/m
  • Bore Diameter 20-200 mm (standard range)
  • Concentricity <0.01 mm TIR
  • Surface Finish Ra 0.4-1.6 μm
  • Tolerance Class IT6-IT7
Standards
ISO 1940-1, DIN 55026, ISO 13041-6, DIN 69893

Industry Taxonomies & Aliases

Commonly used trade names and technical identifiers for Central Bore.

hollow spindle bore center bore machining spindle through-hole CNC lathe bore tool passage diameter bore tolerance standards spindle alignment bar feeder compatibility Central Bore Central Bore in Machinery and Equipment Manufacturing

Parent Products

This component is used in the following industrial products

Hollow Spindle

A hollow cylindrical shaft that transmits rotational motion while allowing passage of fluids, wires, or other components through its center.

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Hub/Centerbody

The central structural component of a swirler that anchors and positions the swirling vanes or passages.

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Engineering Analysis

Risks & Mitigation
  • Concentricity loss causing vibration
  • Internal corrosion from coolants
  • Thermal expansion mismatches
  • Fatigue cracking at bore edges
  • Contamination-induced scoring
FMEA Triads
Trigger: Abrasive particle accumulation
Failure: Progressive diameter enlargement and surface scoring
Mitigation: Install multi-stage filtration systems, implement magnetic chip separators
Trigger: Improper tool holder insertion
Failure: Impact damage to bore entrance chamfers
Mitigation: Use guided tool changers, implement insertion force monitoring
Trigger: Thermal gradients during operation
Failure: Bore distortion affecting concentricity
Mitigation: Integrate spindle cooling systems, implement warm-up cycles

Industrial Ecosystem

Compatible With

Interchangeable Parts

Compliance & Inspection

Tolerance
Geometric tolerances per ISO 1101:2017, diameter tolerances per ISO 286-2:2010
Test Method
CMM verification per ISO 10360-2, air gauge bore measurement, laser alignment testing per VDI 2617

Procurement Evaluation Criteria

Not customer reviews or live demand data. These dimensions support RFQ preparation and supplier evaluation.

Technical documentation
4/5
Manufacturing capability
4/5
Inspection readiness
5/5
Supplier transparency
3/5

These scores are example evaluation dimensions, not real customer ratings, country-specific buyer feedback, or live inquiry activity.

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Frequently Asked Questions

How does central bore diameter affect machining capabilities?

Bore diameter determines maximum bar stock size for turning operations and tool shank clearance for live tooling. Larger diameters reduce spindle stiffness but enable bigger workpiece handling.

What maintenance prevents central bore degradation?

Regular cleaning with non-abrasive tools, inspection for scoring/ovalization, monitoring coolant contamination, and verifying concentricity during preventive maintenance cycles.

Can central bores be repaired if worn?

Limited honing/grinding is possible within tolerance limits, but excessive wear typically requires spindle replacement or specialist boring/coating restoration.

Can I contact factories directly?

Yes, each factory profile provides direct contact information.

Data Basis

CNFX manufacturer profiles, technical classification, publicly available product information, and ongoing plausibility checks.

Preliminary Technical Classification
This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

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