Side-Lock Modular Drill With Spring Bump-Off Tip Retention
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Solution Overview
Problem
Conventional drills with replaceable cutting tips face deformation and failure due to stress concentration in the retaining and drive structure, limiting their service life.
Innovation Solution
A rotary cutting tool design featuring a shank with a pocket that receives an interchangeable cutting tip via an interference fit, where the centering walls are oriented at a non-zero angle, and a spring assembly that displaces the cutting tip between clamped and bump-off positions, reducing stress and improving torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional retaining and drive structure is used in drills with replaceable cutting tips, then the drill can be manufactured and operated, but stress concentration occurs during service leading to deformation and failure
Solution Approach 1:
The cutting head is segmented into a cutting tip and a shank with separate retaining structures. The cutting tip includes a body with cutting edges and a shank with a retaining structure, allowing the cutting tip to be replaced independently while distributing stress away from the main drill body.
Solution Approach 2:
The retaining structure utilizes angular orientation of side walls relative to the longitudinal axis, creating a multi-dimensional stress distribution. The side walls are oriented at angles between 10-45 degrees to the longitudinal axis, transforming axial stress into radial and tangential components that are better distributed throughout the structure.
2Power
If the cutting tip is firmly retained in the shank, then torque transmission is improved, but stress concentration increases leading to earlier failure
Solution Approach 1:
The retaining structure provides localized frictional engagement through specifically oriented side walls that contact the cutting tip. This localized frictional retention transmits torque effectively while concentrating the retaining force in specific angular zones rather than distributing it uniformly, reducing overall stress concentration.
Solution Approach 2:
The spring element pre-compresses the cutting tip against the retaining structure before torque is applied during drilling. This preliminary compressive force establishes optimal frictional contact and stress distribution in advance, allowing the structure to better withstand subsequent torque loads without exceeding strength limits.
3Power
If the cutting tip is retained with high friction, then torque transmission improves, but removal and replacement of the cutting tip becomes difficult
Solution Approach 1:
The retaining structure transitions from a static high-friction engagement to a dynamic system with adjustable retention. The spring element provides continuous compressive force for torque transmission during drilling, but allows controlled release when axial bump-off force is applied, enabling easy removal and replacement of the cutting tip.
Solution Approach 2:
The bump-off mechanism allows the cutting tip to be quickly removed by applying a sudden axial force that overcomes the spring compression and frictional retention in a single rapid motion. This skipping action bypasses the need for gradual unscrewing or prying, making replacement fast and simple.
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
This design enhances the service life of the drill by reducing stress concentrations and maintaining face-to-face contact between the cutting insert and shank, thereby improving torque transmission and stability.
Implementation Method 1
a spring assembly which displaces the interchangeable cutting tip between the clamped position and the bump-off position
Implementation Method 2
the shank comprising a pocket which receives the interchangeable cutting tip via an interference fit
Data Source
AI summary
A rotary cutting tool with a shank and an interchangeable cutting tip, wherein the shank includes a pocket which receives the interchangeable cutting tip via an interference fit. The pocket includes two centering wall portions which, when viewed along a central longitudinal axis, are oriented at a first angle with respect to one another, the first angle being greater than zero. The interchangeable cutting tip is axially displaceable between: an initial position, assumed upon being received in the pocket of the shank; a clamped position, wherein the interchangeable cutting tip is fixedly held with respect to the shank; and a bump-off position, wherein the interchangeable cutting tip is not fixedly held. A holding element holds the interchangeable cutting tip in the clamped position, and a spring assembly which displaces the interchangeable cutting tip between the clamped position and the bump-off position. Other variants and embodiments are broadly contemplated herein.