Small-Diameter Drill Coating and Thinning for Chip Clogging
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Solution Overview
Problem
Small-diameter elongated drills face challenges with breakage resistance and wear resistance due to chip clogging, despite existing technologies like JP 2004-122295 A, which may not be sufficient for improving these aspects.
Innovation Solution
A small-diameter drill design featuring a thinning part at the inner periphery of the chip discharge groove and a hard coating with specific skewness and droplet distribution, applied using a high-power sputtering method, to enhance breakage resistance and wear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the drill is elongated to reduce the number of steps and improve productivity, then productivity is improved, but breakage resistance deteriorates due to chip clogging
Solution Approach 1:
The patent applies local quality by creating a thinning part at a specific location (inner periphery of the chip discharge groove tip part) with different properties than the rest of the drill body. This localized thinning reduces the risk of chip clogging at the critical groove tip region while maintaining the overall elongated structure for productivity, thus resolving the contradiction between productivity and breakage resistance.
Solution Approach 2:
The thinning part is formed in advance during manufacturing to prevent chip clogging before it occurs during drilling operations. By preliminarily creating the thinner section at the groove tip, chips are prevented from accumulating and causing breakage, allowing the elongated drill to maintain both high productivity and breakage resistance.
2Object-generated harmful factors
If the margin length is increased to improve chip discharge, then chip discharge is improved, but the drill becomes more prone to breakage due to reduced structural integrity
Solution Approach 1:
The thinning part creates a localized variation in the chip discharge groove structure, making the tip part thinner than the rest of the groove. This local modification improves chip discharge at the critical tip region without requiring an overall increase in margin length that would compromise the drill's structural integrity and breakage resistance.
3Reliability
If a hard coating is applied to improve wear resistance, then wear resistance is improved, but the coating may cause chip clogging if the surface roughness is not properly controlled
Solution Approach 1:
The patent applies parameter changes by precisely controlling the surface roughness parameters of the hard coating (Sk ≤ 0.015 μm, Ssk ≤ -0.5) to achieve an optimal balance. This controlled surface finish provides sufficient wear resistance while preventing chip clogging by ensuring the coating surface is smooth enough to allow chips to pass through without adhering, thus resolving the contradiction between wear resistance and chip clogging prevention.
4Object-generated harmful factors
If the chip discharge groove surface is smoothed to prevent chip clogging, then chip clogging is reduced, but the groove becomes weaker and more prone to breakage
Solution Approach 1:
The thinning part creates a localized region with different structural properties at the groove tip. This local modification allows the groove to have sufficient strength in the main body while the thinned tip region is optimized for chip discharge, preventing both chip clogging and overall groove breakage through differentiated local characteristics.
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
The design effectively suppresses chip clogging, stabilizes tool wear, and reduces sudden breakage, achieving excellent breakage resistance and wear resistance even in elongated drills.
Implementation Method 1
a hard coating with specific skewness and droplet distribution, applied using a high-power sputtering method
Data Source
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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.