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Involute Splines: Types, Design Considerations, Materials, and Applications

January 22, 2020

Splines are driven shafts that work by interlocking the grooves of one piece with the teeth of a mating bushing. They are used to facilitate the transmission of rotary motion between two shafts and maintain the alignment of two mated components. Depending on the design requirements and configuration of the system, industry professionals employ a variety of different splines, such as involute splines.

What Are Involute Splines?

Involute splines feature short and equally spaced teeth that allow for greater strength with more centered stress distribution. They are one of the most commonly used types of spline shaft due to their tendency to self-center, enhanced structural strength, and ease with which they can be adjusted to a variety of dimensions. Types available include:

  • Major diameter involute splines
  • Fillet root involute splines
  • Flat root involute splines

Design Considerations for Involute Splines

When designing and selecting an involute spline for an application, there are several factors that designers and engineers should keep in mind to ensure optimal performance. These factors include:

  • Thickness and the height of the teeth. The height and thickness of the teeth on a spline are calculated based on the root strength of the spline and the expected torque requirements of the application.
  • Pressure angle of the application. Splines are generally available in pressure angles of 30, 37.5, and 45 degrees. Size and pressure angle are determined based on the desired tooth engagement and spline fit.
  • Coupling configuration. Splines can be constructed in either side-fit or major diameter couplings. Major diameter couplings have a more precise fit requirement than side-fit splines and are less capable of self-alignment. Additionally, they are less forgiving of size deviations for internal and external spline components, while side-fit splines can work within greater size tolerances. Ideally, the teeth and grooves of mated parts should mesh precisely with little or no space between them.

Construction Materials for Involute Splines

Involute splines require materials that offer both strength and durability. Due to these requirements, they are generally composed of either carbon steel or stainless steel.

At Grob, Inc., our standard splines are cold formed from 1117 mild steel, but, depending on the needs of the customer, other materials are available. By employing our proprietary Grob Rolling Process, we enhance both the torsional strength and surface finish of our products.

Advantages of Involute Splines vs. Straight-Sided Splines

Compared to straight-sided (i.e., parallel) splines, involutes splines offer several advantages, including:

  • Simpler design, which allows for easier—and thereby cheaper—manufacturing operations
  • Greater contact area along the tooth profile, resulting in smoother operation
  • Higher tolerance for misalignment

Applications of Involute Splines

They are used in applications across a wide range of industries, including but not limited to:

  • Aerospace
  • Automotive
  • Energy generation
  • Manufacturing equipment
  • Military
  • Mining
  • Oil and gas
  • Robotics

Standard and Custom Splines Shafts From Grob

For over five decades, Grob, Inc. has been a pioneer of cold forming technology. Our experience in manufacturing allows us to produce high-quality bar stock—including involute spline shafts— for a wide range of industrial applications. For more information on our standard or custom cold forming capabilities or to receive a quote, contact us today.