Chamfered End Mill Geometry for Fatigue-Resistant Orbital Drilling
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Solution Overview
Problem
Conventional orbital drilling using an end mill results in deteriorated fatigue strength of fastened parts, particularly in aluminum alloys, when compared to drilling with a drill and reamer, leading to reduced reliability in fastening applications.
Innovation Solution
An end mill design featuring a shank with peripheral and bottom cutting edges, including a chamfered edge on the first ridgeline between the rake face and flank of the peripheral cutting edge, and a honed edge on the peripheral cutting edge, which generates compressive residual stress and improves cutting edge strength during orbital drilling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If orbital drilling is performed using a conventional end mill, then drilling speed and hole quality are improved, but fatigue strength of the fastened part deteriorates
Solution Approach 1:
The patent applies local quality by forming a chamfered edge specifically at the ridgeline between the rake face and flank of the peripheral cutting edge. This localized geometric modification creates compressive residual stress precisely where needed (at the hole entrance and along the cutting edge) without altering the overall orbital drilling process, thereby improving fatigue strength while maintaining drilling efficiency
Solution Approach 2:
The patent changes the geometric parameters of the cutting edge by introducing a chamfered edge with specific dimensions (chamfer width W and angle β). This parameter modification transforms the stress distribution at the cutting edge, generating compressive residual stress that enhances fatigue strength while preserving the high-speed drilling capability of orbital drilling
2Productivity
If orbital drilling is performed using a conventional end mill, then processing efficiency is improved, but manufacturing precision of the hole quality deteriorates
Solution Approach 1:
The chamfered edge is introduced as a localized geometric feature at the peripheral cutting edge ridgeline. This local modification improves the overall hole quality by reducing surface defects and improving surface finish at the critical hole entrance region, without compromising the high processing efficiency of orbital drilling
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 end mill design enhances the fatigue strength of through holes by inducing higher compressive residual stress, allowing for reliable fastening and maintaining high processing accuracy, even in materials like aluminum alloys, while maintaining the speed and quality benefits of orbital drilling.
Implementation Method 1
At least a chamfered edge is formed on a first ridgeline between a first rake face and a first flank of the first cutting edge... induces higher compressive residual stress
Data Source
AI summary
According to one implementation, an end mill for orbital drilling includes: a shank; a first cutting edge formed in a peripheral portion of the shank; and a second cutting edge formed in a bottom portion of the shank. At least a chamfered edge is formed on a first ridgeline between a first rake face and a first flank of the first cutting edge.