Keyways/Splines: Pressure Angle 30°, 37.5°, 45°

Component Specifications

Definition

Keyways are longitudinal slots cut into shafts and mating components that accommodate rectangular keys to transmit torque. Splines are a series of axial ridges or teeth on a shaft that mesh with grooves in a mating hub, providing a more uniform torque distribution and allowing axial movement while maintaining rotational synchronization. Both are critical for connecting rotating elements like gears, pulleys, and couplings to shafts in mechanical systems.

Working Principle

Keyways work by inserting a key into matching slots on both shaft and hub, creating a positive mechanical lock that transfers torque through shear forces. Splines operate through multiple interlocking teeth that distribute torque evenly across the circumference, reducing stress concentrations. The geometric engagement prevents slippage while maintaining precise alignment between connected components.

Materials

Typically manufactured from alloy steels (AISI 4140, 4340), carbon steels (1045, 1144), or stainless steels (304, 316). Surface treatments include carburizing, nitriding, or induction hardening to achieve surface hardness of 45-60 HRC with core toughness.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Fit Class	ANSI B92.1, DIN 5480, ISO 4156
Keyway Types	Rectangular, Square, Woodruff, Taper
Module/Pitch	0.5-10 mm
Spline Types	Involute, Straight-sided, Serrated
Pressure Angle	30°, 37.5°, 45°
Surface Finish	Ra 0.8-3.2 μm
Tolerance Grade	IT6-IT8

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 4156, DIN 5480, ANSI B92.1, JIS B 1601

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.

View Product Details

Engineering Analysis

Risks & Mitigation

Stress concentration at keyway corners
Improper fit causing fretting wear
Misalignment leading to uneven load distribution
Fatigue failure from cyclic loading
Corrosion in harsh environments

FMEA Triads

Trigger: Insufficient interference fit
Failure: Relative movement between shaft and hub
Mitigation: Precise tolerance control per ISO standards, proper press fit calculations

Trigger: Sharp corners in keyway design
Failure: Stress concentration and crack initiation
Mitigation: Radius corners (typically 0.010-0.020 inches), fillet design optimization

Trigger: Material mismatch in hardness
Failure: Premature wear or galling
Mitigation: Maintain proper hardness ratio (shaft slightly harder than key), surface treatments

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Keyways: ±0.002 inches width tolerance, Splines: IT7 grade for major/minor diameters

Test Method

Coordinate Measuring Machine (CMM) verification, optical comparator inspection, functional gaging per ANSI B4.2, surface roughness testing per ISO 4287

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

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Manufacturers of Keyways/Splines

Manufacturer profiles associated with Keyways/Splines.

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Frequently Asked Questions

What is the difference between keyways and splines?

Keyways use a single rectangular key in slots for torque transmission, while splines use multiple interlocking teeth around the entire circumference for more uniform load distribution and potential axial movement.

When should I use splines instead of keyways?

Use splines for higher torque applications, when axial movement is required during operation, or when precise angular positioning is critical. Keyways are suitable for moderate torque applications where cost is a primary concern.

What are the common failure modes of keyways?

Common failures include key shearing, keyway deformation (broaching), fretting corrosion, and stress concentration cracks at keyway corners due to improper fit or overload.

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.

Keyways/Splines