Double-Margin Micro Drill Coating for Chip Clog Resistance
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Solution Overview
Problem
Small-diameter elongated drills face challenges in breakage resistance and wear resistance due to chip clogging, despite existing solutions like surface roughness optimization in chip discharge grooves.
Innovation Solution
The drill features symmetrically formed chip discharge grooves with intersecting ridgeline cutting edges, a hard coating with controlled skewness, and a manufacturing method including sputtering and polishing to enhance breakage resistance and wear stability, along with a second margin part for sliding contact during machining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the drill is elongated to increase working depth, then productivity is improved, but breakage resistance deteriorates due to chip clogging
Solution Approach 1:
The patent applies different surface properties to different regions of the drill. Specifically, the chip discharge groove is given a maximum height of 1.5S or less to prevent chip clogging, while the cutting edge is given a maximum height of 3.0S or more to maintain cutting performance. This local differentiation of surface quality allows the drill to be elongated for increased productivity while maintaining breakage resistance through optimized chip discharge.
2Duration of action of stationary object
If the margin length is increased to improve wear resistance, then duration of action is improved, but device complexity increases
Solution Approach 1:
The patent optimizes the margin length parameter to be 0.5 mm or more, which provides sufficient wear resistance for elongated drills without requiring complex structural modifications. By carefully controlling this dimensional parameter rather than adding complex structures, the patent achieves improved durability while maintaining relatively simple device architecture.
3Reliability
If surface roughness is optimized to promote chip discharge, then breakage resistance is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies that the chip discharge groove surface should have a maximum height of 1.5S or less, which is a preliminary surface preparation requirement. This pre-established surface quality condition ensures that chips can be discharged smoothly during drilling operations, preventing chip clogging that would lead to breakage. By setting this surface roughness criterion in advance, the patent simplifies the overall manufacturing process while achieving improved reliability.
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 configuration effectively suppresses chip clogging, stabilizes tool wear, and reduces sudden breakage, ensuring excellent breakage resistance and tool longevity even in elongated drills.
Implementation Method 1
a hard coating is provided on a surface of the drill body
Implementation Method 2
a surface of the hard coating in the chip discharge groove has skewness (Ssk) defined in ISO25178 of less than 0
Data Source
AI summary
A small-diameter drill in which is a double margin having a diameter of 2 mm or less and a ratio of a margin length to a diameter of 3 or more, in which the margin length L in an axial direction from an outer peripheral end of a cutting edge to the rear ends of first and second margin parts and a ratio L/D to a diameter D are 3 or more, in which at least a surface of a chip discharge groove is provided with a hard coating made of nitride, in which a surface of the hard coating in the chip discharge groove has skewness (Ssk) defined in ISO25178 of less than 0, and in which the number of droplets having an equivalent circle diameter of 1.0 μm or more is 5 or less per 100 μm2 in cross-section observation of the hard coating.