Crankpin/Eccentric Journal: Diameter Tolerance h6/h7 (ISO)

Component Specifications

Definition

The crankpin or eccentric journal is a precisely machined cylindrical surface offset from the main rotational axis of an eccentric shaft or crankshaft. This offset creates an eccentricity that transforms continuous rotary input into controlled linear or oscillating output motion through connecting rods or linkages. In industrial applications, it serves as the critical interface between rotating shafts and reciprocating components in engines, pumps, compressors, and various mechanical systems.

Working Principle

Operates on the eccentric motion principle where the offset distance (eccentricity) between the journal center and shaft rotational axis creates a crank mechanism. As the shaft rotates, the journal follows a circular path, converting rotational energy into linear displacement through attached linkages. The mechanical advantage depends on the eccentricity radius and angular position.

Materials

Typically forged or machined from alloy steels (AISI 4140, 4340, EN19) with surface hardening (case hardening, induction hardening, nitriding). High-wear applications may use hardened tool steels or incorporate wear-resistant coatings (chrome plating, thermal spray coatings). Corrosion-resistant applications utilize stainless steels (17-4PH, 316L).

Technical Parameters

Parameter	Typical range	Notes & selection driver
Hardness	55-62 HRC (surface)
Roundness	0.005 mm max
Cylindricity	0.008 mm max
Eccentricity	±0.02 mm
Surface Finish	Ra 0.4-0.8 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 748, ISO 1101, DIN 7190

Parent Products

This component is used in the following industrial products

Eccentric Shaft / Crank

A mechanical component that converts rotary motion into oscillating or reciprocating motion through its offset axis of rotation.

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Engineering Analysis

Risks & Mitigation

Fatigue failure from cyclic loading
Wear and clearance increase
Lubrication failure leading to seizure
Imbalance causing vibration
Corrosion in harsh environments

FMEA Triads

Trigger: Insufficient lubrication or contaminated lubricant
Failure: Increased friction, overheating, and eventual seizure
Mitigation: Implement scheduled lubrication maintenance, use filtration systems, monitor oil temperature and pressure

Trigger: Cyclic loading exceeding fatigue strength
Failure: Crack initiation and propagation leading to fracture
Mitigation: Proper material selection, surface treatments, regular non-destructive testing (ultrasonic, magnetic particle)

Trigger: Misalignment during assembly or operation
Failure: Uneven wear, increased vibration, reduced efficiency
Mitigation: Precision alignment procedures, use of alignment tools, regular vibration monitoring

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Geometric tolerances per ISO 1101, dimensional tolerances per ISO 286-2, surface finish requirements per ISO 1302

Test Method

Dimensional verification with CMM, hardness testing (Rockwell/Vickers), surface roughness measurement, non-destructive testing (ultrasonic, dye penetrant), dynamic balancing

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

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Supplier transparency

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Manufacturers of Crankpin/Eccentric Journal

Manufacturer profiles associated with Crankpin/Eccentric Journal.

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Frequently Asked Questions

What is the difference between a crankpin and eccentric journal?

While functionally similar, crankpins typically refer to components in multi-cylinder engines where they connect rods to crankshafts, while eccentric journals are single-offset features on shafts for creating reciprocating motion in various industrial machines.

How is eccentricity measured and controlled?

Eccentricity is measured as the radial distance between the journal center and shaft rotational axis using coordinate measuring machines (CMM) or dial indicators. Control is maintained through precision machining, balancing, and strict tolerance adherence.

What maintenance do crankpins require?

Regular lubrication, wear inspection, clearance checks, and balancing verification. High-cycle applications may require periodic re-machining or replacement due to fatigue and wear.

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.

Crankpin/Eccentric Journal