Multi-Stepped Drill Bit Tip for Low-Force Metal Piercing
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Solution Overview
Problem
Existing drill bits and pilot drill bits face challenges when forming holes in metal workpieces, particularly requiring high axial force to pierce the workpiece, which can cause jolting, damage to the drill bit and workpiece, and uncontrolled holesaw movement, leading to potential damage and inefficiency.
Innovation Solution
A drill bit with a multi-stepped tip design, featuring a shank, intermediate fluted portion, and a multi-stepped tip portion with axial and radial reliefs, allowing for smoother cutting, reduced axial force requirement, and improved durability, which can be used alone or as a pilot drill bit with a holesaw to prevent uncontrolled contact and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-step pilot tip is used to pierce the workpiece, then the drill bit can penetrate through the workpiece, but a large amount of axial force is required which causes jolting, damage to the drill bit and workpiece, and uncontrolled holesaw movement
Solution Approach 1:
The pilot tip is segmented into multiple steps (first step, second step, third step) with progressively larger diameters. Each step engages the workpiece at a different stage of penetration, distributing the cutting action and reducing the peak axial force required. The multi-stepped configuration allows the drill bit to gradually penetrate the workpiece rather than requiring a single high-force piercing action.
Solution Approach 2:
The invention changes the geometric parameters of the pilot tip by creating multiple steps with different diameters and axial positions. The first step has a smaller diameter and engages first, the second step has a medium diameter, and the third step has the largest diameter among the steps. This parameter variation allows progressive engagement with the workpiece, controlling the cutting process and reducing harmful axial force spikes.
2Productivity
If high axial force is applied to make the pilot bit penetrate through the workpiece, then penetration is achieved, but the holesaw slams into the workpiece causing damage to teeth, workpiece, and drill bit
Solution Approach 1:
The multi-stepped tip performs preliminary cutting action in a controlled sequence before the holesaw contacts the workpiece. The first step initiates penetration with minimal force, the second step continues the penetration at a controlled rate, and the third step completes the pilot hole formation. This preliminary progressive action prevents the need for sudden high-force penetration that would cause the holesaw to slam into the workpiece.
Solution Approach 2:
The multi-stepped configuration acts as a cushioning mechanism by distributing the penetration force across multiple engagement stages. The progressive steps absorb and manage the cutting forces, preventing sudden force transmission to the holesaw and workpiece that would cause damage.
3Device complexity
If a single-step pilot tip is used, then the structure is simple, but the drill bit may walk from the center, mar the workpiece, and break or bend
Solution Approach 1:
The pilot tip is divided into multiple segmented steps rather than a single monolithic structure. This segmentation provides multiple engagement points with the workpiece, improving centering accuracy and preventing walking. The stepped configuration ensures that cutting forces are applied at multiple locations along the axial direction, stabilizing the drill bit during penetration and reducing the risk of bending or breaking.
4Ease of operation
If axial relief is provided on the elongated portions of the steps, then cutting smoothness is improved, but the manufacturing complexity increases
Solution Approach 1:
The invention applies axial relief (tapering) to the elongated portions of the steps, changing the geometric parameters along the axial direction. This relief provides clearance between the step surfaces and the workpiece, improving cutting smoothness and reducing friction. The relief angles are carefully selected to balance cutting performance with manufacturability.
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A drill bit 10 / 110 / 210 includes a shank 28, an intermediate portion 34 with a helical flute 36, and a multi-stepped tip portion 38 extending along the axis. The tip portion includes a cutting tip 42 with a pair of primary cutting edges 44 extending radially outward from the axis, a plurality of steps 46a - 46d each having an elongated portion 50a - 50d and a tapered portion 52a - 52d tapered outward from the elongated portion relative to the axis. The elongated portions progressively increase in diameter from the cutting tip to the intermediate portion. The elongated portion of each step has an axial relief tapered inward toward the axis. A frontmost elongated portion has a first axial relief at a first angle relative to the central axis and a rearmost elongated portion has a second axial relief at a second angle greater than the first angle. The drill bit may be used as a pilot bit together with a holesaw 312 in a system 300.