Keyway or Spline: Pressure Angle 30°, 37.5°, 45°

Component Specifications

Definition

A keyway is a longitudinal slot machined into a shaft or hub to accommodate a key, which prevents relative rotation between the shaft and mounted component. A spline consists of multiple longitudinal ridges (teeth) on a shaft that mesh with grooves in a mating hub, providing higher torque capacity and better alignment than a single keyway. Both are critical for torque transmission in spindle assemblies.

Working Principle

Keyways work by inserting a rectangular key into matching slots on both shaft and hub, creating a positive mechanical lock against rotation. Splines operate through multiple interlocking teeth that distribute torque evenly across the shaft circumference, allowing for both torque transmission and limited axial movement while maintaining precise angular alignment.

Materials

Typically manufactured from alloy steels (AISI 4140, 4340), carbon steels (1045, 1144), or stainless steels (303, 316) with hardness ranging from 28-45 HRC. Surface treatments include nitriding, induction hardening, or chrome plating for wear resistance.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Keyway Types	Rectangular, Square, Woodruff, Gib-head
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 Class	ANSI B92.1, DIN 5480, ISO 4156

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

Spindle

A rotating shaft that transmits torque and motion within a rotary capping head assembly.

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Engineering Analysis

Risks & Mitigation

Shear failure under overload
Wear and fretting corrosion
Stress concentration at keyway corners
Improper fit causing backlash
Fatigue failure from cyclic loading

FMEA Triads

Trigger: Insufficient interference fit
Failure: Backlash and vibration
Mitigation: Precise machining to specified tolerances, proper assembly procedures

Trigger: Over-torque conditions
Failure: Shear failure of key or spline teeth
Mitigation: Torque limiters, proper sizing calculations, regular maintenance inspections

Trigger: Inadequate lubrication
Failure: Accelerated wear and fretting corrosion
Mitigation: Regular lubrication schedule, use of anti-wear additives, proper sealing

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

IT6-IT8 for shafts, H7/h6 fit for keyways, DIN 5480 tolerance classes for splines

Test Method

Coordinate measuring machine (CMM) inspection, gear measurement systems for splines, surface roughness testing, hardness testing

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 Keyway or Spline

Manufacturer profiles associated with Keyway or Spline.

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Frequently Asked Questions

What is the difference between keyway and spline?

Keyways use a single rectangular key for torque transmission, while splines use multiple interlocking teeth that provide higher torque capacity, better alignment, and allow for axial movement.

When should I choose splines over keyways?

Choose splines for high-torque applications, when precise angular alignment is critical, or when axial movement between components is required during operation.

What are common failure modes for keyways and splines?

Common failures include wear, fretting corrosion, shear failure of keys, tooth deformation in splines, and stress concentration at sharp corners.

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.

Keyway or Spline