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

Component Specifications

Definition

A spline is a precision-engineered mechanical element featuring a series of parallel ridges (teeth) machined along the length of a shaft or bore. These teeth engage with corresponding grooves in a mating hub or sleeve to create a positive, non-slip connection for transmitting rotational torque. Unlike keyways, splines provide a multi-tooth contact surface, distributing the load more evenly, which allows for higher torque capacity, reduced stress concentration, and the ability to accommodate axial movement (sliding) between the connected parts. They are critical in applications requiring precise angular alignment and reliable power transfer under dynamic conditions.

Working Principle

Splines operate on the principle of positive mechanical engagement. The external teeth of the shaft interlock with the internal teeth of the mating component. This interlocking creates a form-fit connection that prevents relative rotation, thereby transmitting torque from the driving to the driven element. The multiple teeth in contact distribute the transmitted force across a larger surface area compared to a single key, reducing shear stress and wear. The design often allows for axial sliding motion along the engaged length, enabling functions like gear shifting in transmissions or adjustable positioning in couplings.

Materials

Typically manufactured from high-strength alloy steels (e.g., AISI 4140, 4340, 8620) for durability and fatigue resistance. Surface treatments like carburizing, nitriding, or induction hardening are commonly applied to enhance surface hardness and wear resistance while maintaining a tough core. Corrosion-resistant steels (e.g., stainless grades like 17-4PH) or non-ferrous metals (e.g., aluminum alloys) may be used in specialized, lightweight, or corrosive environments.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Type	Involute, Straight-sided, Serrated
Fit Class	Class 4 (Close), Class 5 (Medium), Class 6 (Free)
Module/Pitch	Defines tooth size (e.g., Module 1, 1.5, 2)
Pressure Angle	30°, 37.5°, 45°
Number Of Teeth	6, 10, 24, 32, etc.
Surface Hardness	58-62 HRC typical for hardened teeth
Tensile Strength	≥ 1000 MPa for alloy steels

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

Parent Products

This component is used in the following industrial products

Torque Transmission Shaft

A mechanical shaft designed to transmit rotational torque between components within a brake/drive unit.

View Product Details

Engineering Analysis

Risks & Mitigation

Tooth wear and fatigue failure due to cyclic loading
Misalignment causing uneven load distribution and premature failure
Insufficient lubrication leading to galling or seizing
Corrosion in harsh environments degrading tooth profile
Improper fit causing backlash, vibration, or fretting

FMEA Triads

Trigger: Inadequate lubrication or contamination
Failure: Accelerated wear, scoring, or galling of tooth surfaces
Mitigation: Implement regular lubrication schedules with appropriate grease/oil; use seals or shields to prevent contaminant ingress; specify surface treatments for wear resistance.

Trigger: Over-torque or shock loading beyond design limits
Failure: Tooth shear, bending fatigue, or permanent deformation
Mitigation: Design with adequate safety factor; use torque limiters or overload protection devices; select materials with high yield and fatigue strength.

Trigger: Misalignment during assembly or operation
Failure: Edge loading, uneven wear, and premature fatigue cracking
Mitigation: Ensure precise machining and alignment during installation; use self-aligning couplings or flexible spline designs; perform regular alignment checks.

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Governed by standards like ISO 4156 and DIN 5480, specifying tolerances for tooth size, profile, and spacing. Typical tooth-to-tooth composite error tolerance ranges from 0.025mm to 0.1mm depending on class.

Test Method

Testing includes dimensional inspection using spline gauges or CMMs, hardness testing (Rockwell C), surface finish measurement, and functional testing under load to verify torque capacity and wear characteristics. Non-destructive testing (e.g., magnetic particle inspection) may check for cracks.

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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CNFX does not score or rank suppliers. Buyers must verify all claims and documents with the legal manufacturer before ordering.

Manufacturers of Spline

Manufacturer profiles associated with Spline.

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Frequently Asked Questions

What is the difference between a spline and a keyway?

A keyway uses a single key in a slot to transmit torque, creating high stress concentration. A spline uses multiple teeth around the circumference, distributing load evenly, allowing higher torque capacity, better alignment, and often permitting axial sliding movement.

What are the main types of splines?

The three primary types are: 1) Involute Splines: Most common, with curved tooth profiles for smooth engagement and high strength. 2) Straight-sided Splines: Simpler profile, easier to manufacture. 3) Serrated Splines: Triangular teeth, often used for lighter loads or indexing.

How is the fit class for a spline determined?

Fit class (e.g., Class 4, 5, 6 per ISO/DIN standards) defines the tolerance between mating teeth. It is selected based on application requirements: closer fits (Class 4) for precise alignment and minimal backlash; looser fits (Class 6) for easier assembly and accommodation of axial movement.

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.

Spline