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.

Calculation Preview

12 Sep 2023
Last Modified
18 Sep 2023
File Size:
252.59 Kb
File Version:
File Author:
Timothy Molitor

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Comments: 1
JohnDoyle[Admin] 8 months ago
A nice debut calculation! I have awarded a three month XLC Pro subscription by way of thanks.