Gears are designed to transmit torque from one shaft in a motor to another. In comparison, spline shafts are designed to fix gears or other mechanical components over the shaft. They facilitate the axial movement of such components over the shaft, and mate with a female-splined gears, bores, or bearings. Spline shafts function as a linear guide if paired with internally-splined bushing and they transmit rotary motion in rotary drive applications.

Spline shafts are employed in a range of diameters and lengths, types of grooves or teeth, and materials.

A spline shaft is chamfered so the ends of the splines are cut at an angle and beveled to avoid stress. As to the diameter of a shaft, it should never be reduced more than what is needed to allow easy mating with components. Typically, spline shafts are made to standardized lengths but they can be cut according to customer specifications.

Spline shafts also have different types of grooves used to transfer torque in different applications. These include parallel key splines (with square profile), involute splines (with tapered ridges), helical splines (with either a parallel or involute teeth, forming a helix pattern), serration splines (with non-involute teeth of an included angle), and crowned splines (with modified teeth for angular misalignment). Splined shafts are usually made with different metals according to the localized stresses between grooves. The most common materials used are:

• Stainless steel - highly resistant alloy, containing chromium or nickel additions.

• Carbon steel - commonly employed for its malleability and lower carbon content of up to 1.7%.

• Alloy steels - these ferrous alloys contain elements including iron, carbon, chromium, nickel, and molybdenum. they include high-strength low-alloy steels, managing steels, hardenable high-alloy steels, and other special alloy steels.

• Aluminium alloys - these have less than half the density of steel but provide good corrosion resistance and toughness at moderate strengths.

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