Accessory Tool Shank Geometry for Torsional Stress Relief
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Solution Overview
Problem
Conventional accessory tools often break at specific points along the shank due to localized stress and discontinuities, leading to reduced durability and operational lifetime.
Innovation Solution
Incorporating a reduced diameter portion between the tool engagement portion and the effector end of the shank, which extends 10% to 45% of the shank's length, to reduce stress concentrations and increase flexibility, along with optional induction tempering to disperse stress risers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the shank has a uniform diameter throughout its length, then the manufacturing process is simple, but the tool breaks at specific points due to localized stress and discontinuities
Solution Approach 1:
The shank is designed with non-uniform diameter, featuring a reduced diameter portion (136) at specific locations between the tool engagement portion and effector end. This local variation in geometry redistributes stress concentrations, preventing breakage at critical points while maintaining overall structural integrity. The reduced diameter section acts as a stress-relief zone that enhances the tool's durability without requiring complete redesign of the entire shank structure.
2Reliability
If the reduced diameter portion is made very long, then stress concentrations are better reduced, but the tool becomes less rigid and may deflect under load
Solution Approach 1:
The reduced diameter portion is optimized with specific dimensional parameters: its length is defined as 10% to 45% of the total shank length, and its diameter is 60% to 90% of the maximum shank diameter. These parameter ranges balance the competing requirements of stress distribution (requiring longer reduced sections) and torsional strength (requiring shorter reduced sections). The specific ratio ranges provide an optimal compromise that enhances impact resistance while maintaining sufficient rigidity for cutting operations.
3Reliability
If material is removed to create the reduced diameter portion, then stress risers are reduced and durability increases, but manufacturing time and material waste increase
Solution Approach 1:
The reduced diameter portion is incorporated into the initial tool form creation process from the stock metal, rather than being added as a separate post-manufacturing step. By planning the material removal pattern in advance during the forming operation, the manufacturing process efficiently creates the stress-relief geometry in one operation sequence, minimizing both material waste and production time while achieving the durability benefits.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The reduced diameter portion enhances the durability and impact resistance of the accessory tool, allowing the effector end to elastically deform and extend the operational lifetime by reducing torsional stress and stress concentrations.
Implementation Method 1
allowing the effector end to elastically deform and extend the operational lifetime by reducing torsional stress and stress concentrations
Implementation Method 2
along with optional induction tempering to disperse stress risers
Data Source
AI summary
An accessory tool includes an adapter end, and a shank coupled to the adapter end and including a first length. The shank includes a tool engagement portion, and a first reduced portion disposed between the tool engagement portion and the adapter end. The first reduced portion has a second length. The shank additionally includes a second reduced portion formed in the tool engagement portion between the first reduced portion and an end of the shank. The second length is 2.5% to 15% of a total length of the accessory tool.