Understanding the Difference between Internal and External Spline Broaching


Manufacturing-wise, broaching is a highly efficient machining process used to form intricate shapes on workpieces. When working with splines, spline broaching is often employed – an approach typically divided into two main categories – internal spline broaching and external spline broaching. We will explore both strategies in depth while discussing their applications and advantages.

Internal Spline Broaching

Internal spline broaching involves the systematic removal of material from an inner surface of a workpiece to form the desired spline shape. This is typically accomplished using a broach explicitly designed to create internal spline profiles, gradually feeding this tool into the workpiece until reaching desired geometry is achieved. An internal spline broaching tool is a specialized cutting instrument designed to remove material from the internal surface of a workpiece, creating detailed spline profiles.

Applications of Internal Spline Broaching

Gear Manufacturing

Internal spline broaching is often employed when fabricating gears compatible with other gears or shafts, exceptionally where mating shafts must also be available.

Power transmission components

Internal splines are frequently employed in power transmission systems to connect shafts, couplings, and other rotating components.

Automotive industry

For instance, many automotive parts requiring internal splines – transmission components and steering system elements – rely heavily on internal splines.

Advantages of Internal Spline Broaching

  • Internal spline broaching ensures accurate and repeatable results, providing precise fit between mating components. With faster production rates than other machining techniques, broaching provides higher precision at reduced production rates than ever.
  • Eliminating multiple tooling setups helps lower production costs in high-volume manufacturing operations, thus saving production costs and increasing productivity.

External Spline Broaching

External spline broaching involves extracting material from the exterior surface of a workpiece using a broach equipped with cutting teeth tailored specifically for external spline profiles, then pulling through to produce desired external spline shapes.

Applications of External Spline Broaching

Shaft Manufacturing

External spline broaching is widely utilized for producing shafts, especially when they must interface with gears, pulleys, or other rotating components.

Hydraulic and pneumatic systems

External spline broaching is often employed in fluid power systems to connect components, including pump and motor shafts. 

Aerospace industry

External spline broaching finds numerous uses within aircraft engine components, landing gear systems, and other aerospace mechanisms.

External Spline Broaching Benefits

  • External spline broaching provides the precise tooth profile necessary for smooth engagement and optimal performance in power transmission systems.
  • External spline broaching offers rapid material removal rates, leading to efficient production processes.
  • Outer spline broaching streamlines manufacturing and reduces production downtime by eliminating multiple tool changes or setups.


Internal and external spline broaching are two distinct methods for machining splines, each offering its benefits and applications. Internal spline broaching is most frequently employed in gear manufacturing and power transmission systems, while external spline broaching is widely utilized in shaft production and fluid power systems. 

Both techniques offer high precision, efficiency, and cost-effectiveness, making them valuable in various industries. Understanding the differences between internal and external spline broaching will assist manufacturers in selecting the optimal method for their production processes for optimized production processes that produce top-quality components.

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