Variable Honing Geometry in Drills for Thin-Plate Shoulder Durability
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Solution Overview
Problem
Conventional drills face challenges in extending tool life due to fracturing issues in the shoulder portion, particularly when drilling thin plates, leading to reduced machining efficiency and surface quality.
Innovation Solution
The drill design incorporates specific honing width conditions for the cutting edge portions, including a gradual decrease in honing width from the boundary between the margin and shoulder cutting edge portions, along with a coating layer containing compounds like Ti, Si, and N, to enhance wear and fracture resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the honing width of the outer peripheral end of the outer peripheral cutting edge is set to be at least 1.5 times greater than the honing width of the web thinning cutting edge, then wear resistance of the cutting edge is improved, but cutting resistance increases and machining accuracy deteriorates
Solution Approach 1:
The patent applies different honing widths to different portions of the cutting edge. Specifically, the honing width at the outer peripheral end (R1) is set to be at least 1.5 times greater than the honing width at the web thinning cutting edge portion (R2). This local differentiation allows the outer peripheral end to have enhanced wear resistance while the web thinning portion maintains lower cutting resistance, thereby resolving the contradiction between wear resistance and machining accuracy.
2Productivity
If the honing width of the shoulder portion is set to be smaller than the honing width of the cutting edge, then cutting resistance is reduced, but strength of the shoulder portion becomes insufficient leading to fracturing
Solution Approach 1:
The patent addresses the potential fracturing issue of the shoulder portion by applying honing treatment in advance. The honing process strengthens the shoulder portion through work hardening and surface refinement, providing preliminary reinforcement before the drilling operation begins. This allows the shoulder portion to maintain sufficient strength to prevent fracturing while still having a smaller honing width than the cutting edge, thereby maintaining low cutting resistance and high productivity.
3Duration of action of stationary object
If honing is performed on the cutting edge to improve wear resistance, then tool life is extended, but the shoulder portion becomes prone to fracturing due to insufficient strength
Solution Approach 1:
The patent applies honing treatment selectively to specific portions of the drill. Honing is performed on the cutting edge (with appropriate honing widths R1 and R2) to improve wear resistance and extend tool life. Meanwhile, the shoulder portion is also subjected to honing treatment, which strengthens this critical area through work hardening and surface refinement, thereby improving fracture resistance. This localized differentiation of honing application resolves the contradiction between extending tool life and preventing shoulder portion fracturing.
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 significantly extends the tool life of the drill by improving wear and fracture resistance, reducing cutting resistance, and maintaining machining accuracy, especially when drilling thin plates.
Implementation Method 1
a coating layer containing a compound of: an element of at least one kind selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al and Si; and an element of at least one kind selected from the group consisting of C, N, O and B
Data Source
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AI summary
A drill in which: a chip discharge groove is formed in an outer periphery of an edge portion serving as a leading end side portion of a drill body; and a cutting edge is formed in an intersecting edge between a rake surface of a leading end side region and a leading end flank of the edge portion, the drill comprising a margin portion, a shoulder portion and a web thinning portion, wherein: the cutting edge comprises, in order from a rotation center, a first cutting edge portion, a second cutting edge portion, a shoulder cutting edge portion, and a margin cutting edge portion; the honing width gradually decreases from the boundary P1 toward the position P2; and the conditions represented by expression (1): honing width of second cutting edge portion ≤ R1 and expression (2): 2.0 < R1/R2 < 5.0 are satisfied.