Flat Drill Bit Geometry for Nail-Resistant Cordless Drilling
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Solution Overview
Problem
Flat drill bits for cordless hand-held electric power tools often suffer from cutting edge fractures when encountering nails in wood materials, and the limited torque and speed of these tools make efficient drilling challenging.
Innovation Solution
A flat drill bit design featuring a stem body with a cut flute part and a threaded guiding part that is conically shaped with external threads, where the cutting edge is inclined at an angle between 84° and 86° relative to the central axis, and the threads have a specific pitch and cone angle to optimize nail cutting and torque coordination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the cutting edge is made perpendicular to the axis for efficient drilling, then drilling speed is improved, but the cutting edge becomes vulnerable to fracture when striking nails
Solution Approach 1:
The cutting edge is designed at an asymmetric angle of 84-86 degrees relative to the drill bit axis, deviating from the conventional perpendicular (90 degree) configuration. This asymmetric angular design allows the cutting edge to strike nails at a glancing angle during lateral impacts, significantly reducing the impact force and preventing fracture while maintaining effective cutting capability during normal drilling operations.
2Stability of the object's composition
If the threaded guiding part has a large diameter for stable guidance, then guidance stability is improved, but the torque requirement exceeds the capability of cordless hand-held electric power tools
Solution Approach 1:
The threaded guiding part diameter is precisely controlled within the range of 0.6-0.8 times the outer diameter of the cutting face. This parameter optimization ensures that the guiding part provides sufficient stability and centering action during drilling, while keeping the torque requirement within the limited capacity of cordless hand-held electric power tools. The specific pitch range of 1.2-1.3mm further optimizes the balance between guidance stability and power consumption.
Data Source
AI summary
A flat drill bit includes a stem body, a cut flute part provided axially from an end of the stem body and being generally flat-shaped, and a threaded guiding part provided axially from an end of the cut flute part. The cut flute part includes two longitudinal wings which are configured to be rotationally symmetrical to each other about a longitudinal central axis (O) of the flat drill bit. Each longitudinal wing is formed with a cutting edge at the end of the cut flute part from which the threaded guiding part extends. A rotating trajectory profile caused by the cutting edge when the flat drill bit rotates is inclined towards the stem body and is at an angle (a) relative to the longitudinal central axis (O), and the angle (a) is in a range between 84° and 86°.