Modular Drill Shank Stress Reduction via Inclined Drive Surfaces
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Solution Overview
Problem
Drills with replaceable cutting tips suffer from premature deformation and failure due to stress concentration in the shank, limiting their service life.
Innovation Solution
Modifications include creating a gap between the frustoconical dovetail of the cutting head and the shank, altering the angle of drive surfaces from radial to inclined, and lengthening the pocket walls to redistribute forces, thereby reducing distortion and increasing the shank's resistance to deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the cutting head directly contacts the shank at all surfaces, then the connection is simple and manufacturing is easy, but stress concentration occurs leading to deformation and failure
Solution Approach 1:
The patent segments the contact interface between the cutting head and shank by introducing gaps at specific locations (forward and rearward areas). This divides the continuous contact surface into discrete contact zones, concentrating stresses in controlled areas rather than distributing them across the entire interface, thereby preventing deformation while maintaining manufacturing simplicity
Solution Approach 2:
The patent applies local quality by creating non-uniform contact characteristics along the interface. Specific regions (forward and rearward areas) have gaps to reduce stress concentration, while other regions maintain contact for force transmission. This localized modification of contact quality prevents failure without compromising overall connection integrity
2Device complexity
If the drive surfaces are oriented radially, then the structure is simple, but stresses are concentrated on the pocket walls causing distortion
Solution Approach 1:
The patent changes the geometric parameter of the drive surface orientation from radial to inclined relative to the radial direction. This parameter modification alters the stress distribution pattern on the pocket walls, redirecting forces to reduce concentration at critical locations and prevent distortion, while maintaining reasonable structural complexity
3Ease of manufacture
If the pocket walls are short with sharp corners, then manufacturing is easier, but stress concentration occurs at corners leading to premature failure
Solution Approach 1:
The patent applies curvature by replacing sharp corners with rounded transitions in the pocket geometry. This curvilinear modification eliminates stress concentration at corner locations by distributing stresses smoothly across curved surfaces, thereby preventing premature failure while maintaining ease of manufacture through standard machining operations
Data Source
AI summary
A drill having a replaceable cutting head, modified to eliminate forces which would distort the pocket of the drill shank and otherwise concentrate stresses which would cause failure of the drill. The cutting head has a frustoconical depending connecting member received in a receptacle formed in the shank. In different embodiments, contact between the pocket formed in the shank and the cutting head connecting member is limited. In one embodiment, angle of drive surfaces is modified from prior art practice. In another embodiment, transition of at curved joints between vertical and horizontal surfaces is made more gradual. The drill preferably has flutes formed collectively by the shank and cutting head when assembled.