Keyed Shaft Design & Strength Analysis (ANSI B17.1)

This calculator's main function is to quickly and intuitively choose the proper machine key for a given shaft, and to obtain all the dimensions needed for design. It also calculates the required length of the key to carry a given load, and gives exact limit dimensions of what the initial shaft keyway must be to achieve a certain post-grind dimension. This specific calculator is based on ANSI B17.1 for Inch shafts.

A key is a common machine element used to connect a shaft to a hub or mating rotating component like a pulley or gear. The key provides the torque transmission between the shafl and hub.

The key sizing and design process involves:

• Determining the torque to be transmitted by the shaft-hub connection based on the power transmission requirements.
• Calculating the equivalent twisting moment acting on the key by dividing the torque by the shaft radius.
• Estimating the preliminary key dimensions - width, height and length based on the shaft diameter as per standards like ANSI B17.1.
• Finding the key material allowable shear stress for the selected key material.
• Calculating the actual shear stress induced in the key using the twisting moment and key dimensions.
• Comparing the actual shear stress to the allowable stress to ensure adequate strength. The factor of safety should be appropriate.
• Analyzing the key for other failure modes - crushing, fracture, etc. based on distortion energy theory.
• Optimizing the key dimensions to satisfy strength requirements while minimizing size and cost. Finish dimensions are finalized.
• Detailing the key-shaft interface for appropriate fit and position tolerances as per standards.

The final key design should transmit the required torque safely while minimizing stress concentrations on the shaft.