Drill Thinning Edge Rake Angle Gradient for Cutting Resistance
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Solution Overview
Problem
Conventional drills face challenges in reducing cutting resistance while maintaining tool life, as large rake angles improve cutting resistance but reduce tool life due to increased chipping risk, and small rake angles fail to sufficiently lower cutting resistance.
Innovation Solution
A drill design with a thinning edge where the rake angle changes along its length, being smaller near the axis and larger near the cutting edge, and a spiral groove configuration, sets the rake angle of the thinning edge within a range of one-fifth to one-half of the helix angle to balance cutting resistance and tool life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the rake angle of the thinning edge is increased to reduce cutting resistance, then the cutting resistance is reduced, but the thinning edge is likely to be chipped due to reduction of strength
Solution Approach 1:
The patent applies local quality by creating different rake angles at different locations along the thinning edge. The thinning edge has a first portion with a smaller rake angle (5-15 degrees) near the axis for strength, and a second portion with a larger rake angle (15-30 degrees) near the cutting edge for reduced cutting resistance. This spatial variation in geometric properties allows each section to optimize for its specific functional requirements.
2Productivity
If the rake angle is set large to improve biting property and reduce cutting resistance, then cutting resistance is reduced, but tool life is shortened due to increased chipping risk
Solution Approach 1:
The patent implements local quality by differentiating the rake angle along the length of the thinning edge. The first portion near the axis maintains a conservative rake angle (5-15 degrees) to ensure strength and prevent chipping, preserving tool life. The second portion near the cutting edge uses a larger rake angle (15-30 degrees) to improve biting property and reduce cutting resistance, enhancing productivity. This localized differentiation resolves the contradiction between tool life and cutting efficiency.
3Reliability
If the rake angle is set small to improve tool life, then tool life is improved, but cutting resistance cannot be sufficiently reduced
Solution Approach 1:
The patent applies local quality by creating a gradient of rake angles along the thinning edge. The first portion has a smaller rake angle (5-15 degrees) that provides sufficient strength to prevent chipping and ensures tool life. The second portion has a larger rake angle (15-30 degrees) that effectively reduces cutting resistance by improving the biting property. This spatial differentiation allows the drill to achieve both long tool life and low cutting resistance simultaneously.
Data Source
AI summary
A drill including a columnar body that is rotated about an axis, a cutting edge that is formed at the tip end of the body, and a thinning edge that is formed continuously with the cutting edge close to the axis of the body, by having a thinning at the tip end of the body. The thinning edge is formed such that a rake angle of the thinning edge relative to the axis of the body changes depending on a location of the thinning edge, where the rake angle of the thinning edge close to the cutting edge is a positive angle larger than that close to the axis of the body.