Is a 2.126 Diameter A2 Tool Steel Shaft Sufficient for 2,500 ft/lbs of Torque?

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    Calculation Torque
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Discussion Overview

The discussion revolves around the adequacy of a 2.126" diameter A2 tool steel shaft, hardened to Rc 48-52, for withstanding a maximum peak torque loading of 2,500 ft/lbs. Participants explore calculations related to torque, stress, and potential fatigue considerations in the context of mechanical design.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant seeks guidance on whether the specified shaft is satisfactory for the given torque loading.
  • Another participant suggests a calculation method involving torque, polar moment of inertia, and allowable shear stress, noting the need to look up specific values for tool steel.
  • A different participant questions the initial method proposed, indicating it may only account for static loading and emphasizes the importance of considering fatigue loading through a comprehensive shaft design process.
  • A participant provides a link to a video resource that may assist in understanding the design considerations better.

Areas of Agreement / Disagreement

Participants express differing views on the adequacy of the proposed calculation method, with some emphasizing the need for a more thorough analysis that includes fatigue considerations. The discussion remains unresolved regarding the sufficiency of the shaft for the specified torque.

Contextual Notes

There are limitations regarding the assumptions made in the calculations, particularly concerning static versus dynamic loading, and the specific values for allowable shear stress that need to be referenced. The discussion does not resolve these aspects.

Who May Find This Useful

Individuals involved in mechanical design, particularly those working with shaft design and torque calculations, may find this discussion relevant.

Indiana Dave
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Good folks, I need some guidance.

I have a shaft in a machine, hardened A2 tool steel- Rc 48-52 that is 2.126" dia., 3" long.

This shaft will see a maximum peak torque loading of 2,500 ft/lbs.

I am hopelessly mired in calculations I do not trust. Can someone weigh in? Is this shaft section satisfactory?

Thanks!
 
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Try this approach:

Torque = J * allowable stress / radius

J = polar moment of inertia = 1/2 * PI * radius^4

allowable shear stress for tool steel - you will need to look up, but probably somewhere between 12 ksi to 20 ksi. If your tool steel is HRC, the yield may be much higher. See if you have MTR for the steel.
 
Last edited:
Hi I'm new here. i just came across this post.

edgepflow,no offence but won't that method account for only static loading?
You might have to go through the whole shaft design process (Free Body Force diagrams-->BM and shear force diagrams-->stress calculation using endurance limit etc.) for fatigue loading(cyclic stress) since it will be mounted in a machine. I'd refer to Shigley's Mechanical Engineering Design book ISBN: 0−390−76487−6. To be honest i experienced MANY problems myself, when i designed my first shaft alone, so i know how it feels.
 

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