Small-Diameter Drill Cutting Edge Curvature and Core Thickness
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Solution Overview
Problem
Small-diameter drills with increased core thickness face challenges in chip processing due to shallow flute depth and low feed rate, leading to reduced strength and machining accuracy, especially when dealing with materials like stainless steel, and conventional designs compromise strength for sharpness.
Innovation Solution
A small-diameter drill with a diameter of 3 mm or less, featuring a flute portion cutting edge curved concave against the rotational direction, with a specific degree of concavity and thinning portion to flute portion length ratio, and a radial rake angle between -5 to -15°, along with core thickness and flute width ratios optimized to maintain strength and sharpness without return machining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the flute portion cutting edge is curved in concave to achieve a positive radial rake angle, then sharpness of the cutting edge is improved, but strength of the outer circumferential portion of the cutting edge is reduced
Solution Approach 1:
The patent applies local quality by differentiating the curvature radius of the flute surface into two zones: a larger curvature radius R1 for the flute surface along the cutting edge (providing sharpness) and a smaller curvature radius R2 for the heel-side flute surface (maintaining strength). This localized differentiation allows each region to optimize its function without compromising the other.
2Strength
If core thickness is increased to ensure strength, then strength is improved, but chip processing becomes difficult due to shallow flute depth and small flute area
Solution Approach 1:
The patent changes the geometric parameters of the flute surface by implementing a dual curvature radius system. The heel-side flute surface has a smaller curvature radius R2 compared to R1 along the cutting edge, which optimizes chip flow characteristics and evacuation efficiency while maintaining the increased core thickness for strength.
3Stability of the object's composition
If feed rate is reduced for rigidity reasons, then rigidity is improved, but chip processing becomes more difficult
Solution Approach 1:
The patent applies local quality by creating different surface characteristics in different flute regions. The heel-side flute surface with smaller curvature radius R2 is specifically optimized to facilitate chip evacuation and processing, compensating for the lower feed rates used to maintain rigidity during small-diameter drilling operations.
Data Source
AI summary
A small-diameter drill having a diameter of φ3 mm or less and an end that has undergone cross thinning is provided such that in a front view, a flute portion cutting edge is curved in concave with a degree of concavity with respect to an imaginary straight line in a range of 0.5 to 2% of a drill diameter, the imaginary straight line connecting the radially outer end of the flute portion cutting edge and the radially outer end of thinning portion cutting edge, the ratio of length of the thinning portion cutting edge to length of the flute portion cutting edge is set to 0.6 to 0.9:1, and in an axially perpendicular cross-sectional view, curvature radius of a heel-side flute surface of the flute is set to be smaller than curvature radius of a flute surface along the flute portion cutting edge.