Pilot Diameter: Diameter Tolerance h6/h7 (ISO)

Component Specifications

Definition

The pilot diameter is a precisely machined cylindrical surface on a coupling hub that serves as a locating feature for proper alignment with mating components. It ensures concentricity between the hub and connected shafts or other coupling elements, minimizing radial runout and vibration while facilitating assembly. This critical dimension maintains the geometric relationship between rotating elements in power transmission systems.

Working Principle

The pilot diameter functions as a mechanical datum surface that establishes precise radial positioning between mating components. During assembly, it guides the hub onto shafts or other coupling elements, ensuring concentric alignment before final fastening. This eliminates eccentricity that could cause imbalance, vibration, or premature wear in rotating machinery.

Materials

Typically manufactured from alloy steels (AISI 4140, 4340), stainless steels (304, 316), or high-strength aluminum alloys (6061-T6, 7075-T6) with hardness ranging from 28-45 HRC depending on application requirements.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Length Ratio	0.5-1.0 x Diameter
Concentricity	0.02-0.05 mm TIR
Surface Finish	Ra 0.8-1.6 μm
Diameter Tolerance	h6/h7 (ISO)

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 286-2, DIN 7150, ANSI B4.1

Parent Products

This component is used in the following industrial products

Coupling Hub

The central connecting element of a shaft coupling that mounts directly onto the shaft ends to transmit torque between rotating components.

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Engineering Analysis

Risks & Mitigation

Misalignment causing vibration
Concentricity errors leading to premature bearing failure
Improper fit resulting in fretting corrosion

FMEA Triads

Trigger: Incorrect machining tolerance
Failure: Poor concentricity and imbalance
Mitigation: Implement statistical process control (SPC) for diameter measurements

Trigger: Material fatigue from cyclic loading
Failure: Cracking or deformation of pilot surface
Mitigation: Use fatigue-resistant materials and proper heat treatment

Trigger: Corrosion in harsh environments
Failure: Diameter enlargement and loss of precision fit
Mitigation: Apply protective coatings or use corrosion-resistant materials

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

ISO 286-2:2010 Geometrical product specifications (GPS)

Test Method

Coordinate measuring machine (CMM) verification per ISO 10360-2

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

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Inspection readiness

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Supplier transparency

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Manufacturers of Pilot Diameter

Manufacturer profiles associated with Pilot Diameter.

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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 primary function of a pilot diameter in coupling hubs?

The pilot diameter ensures precise radial alignment and concentricity between mating components, reducing vibration and wear in rotating machinery.

How does pilot diameter tolerance affect coupling performance?

Tighter tolerances (h6/h7) provide better concentricity and balance, while looser tolerances may cause vibration and reduced service life.

Can pilot diameters be repaired if damaged?

Minor damage can be repaired through precision machining or metal spraying, but severe damage typically requires component replacement.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records. See the editorial policy.

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.

Pilot Diameter