Standard Involute Spline Specifications

Engineering Standards

• The curving profile of an involute spline is similar to a gear tooth except rounded for a smoother mating during rotation. Each spline width is about half the depth of a spline. According to "Machine Design" by U. C. Jindal, "the standard, involute spline-tooth forms have a 20-degree pressure angle. Standard splines can have six to 50 teeth." The tip of the involute spline is rounded instead of a point found in a spur gear or flat face as is found on a helical rack gear.

Standard Design

• "Mechanical Design of Machine Elements and Machines" by Jack Collins, Henry Busby and George Staab states "for standard involute splines in torsion, the value of K (stress) seems to be about 2.8." This is lower than the stress generated when angular gear teeth meet. As pressure angle decreases, the depth of the gear tooth increases.

American Design Standards

• Involute spline requirements are defined by American National Standards Institute standards B92.1 and B92.M. ANSI B92.1 defines how to inspect involute splines for wear and tear. This standard is shared by the Society of Automotive Engineers. Gear requirements are defined by American Society of Mechanical Engineers standard Y14.7. It defines the standards for spur, helical and rack gear drawings. ASME Y14.7.2 defines how to draw spline gears as well as bevel and hypoid gears. ASME standards require at least six teeth on the gear. ASME standards recommend a pressure angle of 30 degrees and a short, cut tooth.

International Design Standards

• Deutsches Institut für Normung, based in Germany, issues standards that become a European standard. Standard DIN 5480-15 gives formulas on how to create, guide and inspect involute splines. Unlike American standards, the DIN standard is metric. The International Standards Organization has issued standard ISO 10230. It defines the mating dimensions for splined hub and sprocket gears, including involute splines. These mating dimensions define how involute spline gear teeth will touch or mate.