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INDUSTRY COMPONENT

Internal Bore

Internal bore is a precision-machined cylindrical cavity within the Kelly Bar that facilitates fluid transfer and structural integrity in drilling operations.

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Component Specifications

Definition

The internal bore is a critical cylindrical passage machined through the length of the Kelly Bar, designed to allow the flow of drilling fluid (mud) from the surface to the drill bit. It maintains precise dimensional tolerances to ensure efficient fluid dynamics, structural support under torsional and axial loads, and compatibility with mating components in rotary drilling systems.

Working Principle

The internal bore operates by providing a sealed conduit for high-pressure drilling fluid transmission, which cools the drill bit, removes cuttings, and stabilizes the borehole. Its smooth, concentric geometry minimizes fluid friction and pressure loss while maintaining the bar's torsional rigidity during rotation.

Materials

High-strength alloy steel (e.g., AISI 4140 or 4340), heat-treated to 28-32 HRC, with optional internal coatings (hard chrome plating or tungsten carbide) for wear and corrosion resistance.

Technical Parameters

Diameter 50-200 mm (standard range)
Tolerance H7/h6 (ISO)
Straightness ≤ 0.1 mm/m
Surface Finish Ra ≤ 1.6 μm
Pressure Rating Up to 35 MPa

Standards

ISO 286-2, DIN 7154, API RP 7G

Industry Taxonomies & Aliases

Commonly used trade names and technical identifiers for Internal Bore.

Parent Products

This component is used in the following industrial products

Kelly Bar

A hollow, square or hexagonal steel bar that transmits torque and vertical force from the drilling rig's rotary table to the drill string in foundation drilling operations.

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Engineering Analysis

Risks & Mitigation

Bore wall erosion from abrasive fluids
Misalignment causing seal failure
Fatigue cracking under cyclic loads

FMEA Triads

Trigger: Abrasive particle accumulation in drilling fluid
Failure: Progressive bore wall erosion leading to leaks
Mitigation: Implement fluid filtration systems and use wear-resistant coatings

Trigger: Improper machining tolerances
Failure: Seal incompatibility and fluid leakage
Mitigation: Adhere to ISO H7/h6 tolerance standards and conduct dimensional inspections

Industrial Ecosystem

Compatible With

Interchangeable Parts

Compliance & Inspection

Tolerance

Geometric tolerances per ISO 1101, diameter tolerance H7/h6

Test Method

Ultrasonic testing for wall thickness, pressure testing per API RP 7G

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

What is the primary function of the internal bore in a Kelly Bar?

It transmits drilling fluid to the drill bit while providing structural integrity under operational loads.

How does bore diameter affect drilling performance?

Larger diameters reduce fluid pressure loss but may compromise torsional strength; optimal sizing balances flow efficiency with mechanical requirements.

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.