Rotary Drill Head Undercut With Rear-Facing Blade for Fiber-Free Hole Exit
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Solution Overview
Problem
Rotary drilling tools struggle to produce high-quality through-holes in fibrous materials like carbon fiber-reinforced plastics, as fibers often protrude into the outlet opening due to incomplete cutting during drilling.
Innovation Solution
A rotary drilling tool with a cutting head featuring a rear-facing blade integrated into an undercut, which engages and cuts protruding fibers when the tool is withdrawn, ensuring complete separation and improving hole quality without compromising the main cutting edge during drilling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional rotary drilling tool with only front-facing cutting edges is used, then the drilling process is simple and fast, but the outlet opening quality deteriorates with fibers protruding into the hole
Solution Approach 1:
The cutting head is segmented into distinct functional zones: a tip-side axial portion for guiding and initial cutting, and a shaft-side axial portion with undercuts containing rear-facing blades for finishing the outlet opening. This segmentation allows each zone to perform its specific function optimally, resolving the contradiction between simple structure and high outlet quality.
Solution Approach 2:
Rear-facing blades are introduced that cut in the opposite direction to the main cutting edges. These blades engage the workpiece material during tool withdrawal, machining the outlet opening from the inside outward. This inverted cutting approach directly addresses the outlet quality issue without complicating the primary drilling function.
2Manufacturing precision
If the rotary drilling tool continuously machines the outlet opening during drilling, then outlet quality improves, but the main cutting edge wear increases and tool life decreases
Solution Approach 1:
The main cutting edges perform preliminary cutting to create the through-hole and rough-out the outlet opening before the tool exits. The rear-facing blades then perform the finishing action during tool withdrawal, when the main cutting edges are no longer engaged with the workpiece. This temporal separation prevents continuous machining by the main cutting edge, reducing wear and extending tool life.
Solution Approach 2:
The cutting action is made dynamic by utilizing both the forward drilling motion and the backward withdrawal motion. The rear-facing blades are positioned to engage the workpiece only during withdrawal, transforming the previously idle return stroke into a productive machining phase. This dynamic utilization of tool motion achieves outlet quality without increasing main cutting edge wear.
Data Source
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AI summary
A rotary drilling tool (10) has a cutting head (12) with at least one tip (22) and a front-facing main cutting edge (24) defining a maximum diameter (D) of the cutting head (12). The cutting head (12) has an undercut (38) with a radially inwardly springing ledge (44) with a rear-facing blade (42) provided for cutting when pulling the rotary drilling tool (10) out of a workpiece. Method for producing a through-hole in a workpiece by means of such a rotary drilling tool (10).