Multi-Piece Cutting Tool Thread Geometry for Axial Force Transfer
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Solution Overview
Problem
Existing multi-piece cutting tools with conventional thread profiles risk damaging brittle components, such as cemented carbide, due to radially outward forces during tightening, which can cause cracking.
Innovation Solution
A multi-piece tool assembly with a thread design where the male and female threaded components have abutment surfaces with perpendicular and non-perpendicular components, aligning axes and preventing over-tightening, ensuring forces are transmitted along the axis, reducing the risk of damage to the female component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional thread profiles are used in multi-piece cutting tools, then the tool assembly can be secured together, but radially outward forces during tightening can damage brittle components like cemented carbide
Solution Approach 1:
The thread profile geometry is changed from conventional designs to a specific configuration where the thread flanks are oriented to transmit forces axially rather than radially. This parameter change in the thread angle and flank orientation ensures that tightening forces are directed along the tool assembly axis, eliminating harmful radial components that could crack brittle cemented carbide components
Solution Approach 2:
The thread design employs asymmetric flank angles where the loading and unloading flanks have different orientations. This asymmetry is specifically configured so that the load-bearing flank transmits forces axially through the thread engagement, while the other flank is optimized for smooth engagement and disengagement, thereby directing stress away from radial components
2Strength
If brittle materials like cemented carbide are used for cutting inserts, then cutting performance is improved, but the risk of breakage and cracking increases
Solution Approach 1:
The thread design incorporates force direction control that acts as a preventive measure before tightening occurs. By pre-configuring the thread geometry to channel forces axially, the design cushions the brittle cemented carbide insert from radial stress concentrations that would otherwise precede and cause cracking during the tightening process
Solution Approach 2:
The physical state of stress distribution is changed by modifying the thread engagement parameters. The specific thread flank angles and engagement depth are optimized to ensure that stress is distributed uniformly along the axial direction, preventing localized stress concentrations that could initiate cracks in the brittle material
3Ease of operation
If thread forces extend at angles to the longitudinal axis, then threading engagement is achieved, but damage risk to female components increases
Solution Approach 1:
The thread angle parameter is specifically optimized so that the resultant force vector during engagement aligns with the longitudinal axis. This parameter adjustment ensures that while threading engagement occurs smoothly, the force components remain axial rather than angular, eliminating harmful lateral forces on female components
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A multi-piece tool assembly includes a male threaded member having an external thread, and a female threaded member having an opening adapted to receive at least part of the male threaded member up to a predetermined depth and an internal thread adapted to mate with the external thread of the male threaded member. When the male threaded member is received in the opening to the predetermined depth, substantially all forces between the external thread and the internal thread are oriented along an axis of the female threaded member, a working portion of the tool assembly being provided on one of the male threaded member and the female threaded member.