Self-Drilling Threaded Fastener With Burr-Removing Thread Gaps
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Solution Overview
Problem
Self-drilling screws used in the construction industry often create burrs when penetrating sheet metal, leading to rust stains and damage to sealing washers, which can result in leaks.
Innovation Solution
A self-drilling, anti-burr threaded fastener design featuring a unique thread configuration with specific angles and gaps to minimize burr formation, along with knurling and a tapered shaft to enhance sealing and burr removal, is introduced.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a self-drilling screw is used to penetrate sheet metal, then the screw can securely attach materials, but burrs are formed that cause rust stains and damage sealing washers
Solution Approach 1:
The thread is divided into three distinct portions: a first thread portion with a first helical thread for initial engagement, a second thread portion with a second helical thread for continued fastening, and a third thread portion with a third helical thread featuring gaps that act as burr removal surfaces. This segmentation allows each portion to perform its specific function, with the third portion specifically designed to eliminate burrs that would otherwise damage sealing washers and cause rust stains.
Solution Approach 2:
The invention converts the harmful burr formation into a beneficial process by designing the third helical thread with gaps that create burr removal surfaces. The burrs formed during self-drilling are subsequently removed by these surfaces, transforming the harmful effect into a controlled process that actually improves sealing effectiveness by eliminating burrs that would damage the sealing washer.
2Strength
If a self-drilling screw creates burrs during penetration, then the screw achieves secure attachment, but the burrs extend beyond the sealing washer and cause rust staining
Solution Approach 1:
The third thread portion with gaps is designed to perform burr removal action before the sealing washer is fully compressed. The gaps in the third helical thread create surfaces that remove burrs during the fastening process, preventing them from extending beyond the sealing washer and causing rust stains later.
3Reliability
If a self-drilling screw penetrates sheet metal, then fastening is achieved, but burrs damage the rubber sealing washer resulting in leaks
Solution Approach 1:
The third thread portion is specifically designed with gaps to create burr removal surfaces at the precise location where burrs would otherwise damage the sealing washer. This localized solution addresses the specific problem of burr damage without affecting the overall fastening function performed by the first and second thread portions.
Data Source
AI summary
A self-drilling, anti-burr, threaded fastener is provided having at least two different thread portions. The first thread portion extends along the tip and the second thread portion extends along the tapered portion adjacent to the tip. A third thread portion can be provided between the first and second thread portions that includes a plurality of axial gaps that extend to the thread root to remove burrs. Alternatively, knurling is provided in an area where the first and second thread portions meet, and the knurling acts to remove burrs.