Stepped CLT Drill Bit for Cleaning Obscured Fastener Openings
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Solution Overview
Problem
Pre-drilled holes in Cross Laminated Timber (CLT) panels become partially blocked or obscured due to shifting of wood layers during transportation, making it difficult to insert dowels and compromising the structural integrity of the connection.
Innovation Solution
A drill bit with strategically designed cutting edges and flutes is used to clean up the openings in CLT panels, ensuring each section remains concentric about a single axis without enlarging the opening, allowing dowels to be properly inserted and secured with adhesive for strong structural joints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a standard drill bit is used to drill fastener openings in cross laminated timber, then the drill bit can penetrate the material, but the fastener openings become obscured by material buildup preventing proper fastener insertion
Solution Approach 1:
The drill bit is segmented into multiple cutting edges arranged in a stepped configuration around the circumference, with each edge responsible for a portion of the material removal process. This segmentation allows the cutting edges to work in sequence, progressively cleaning the hole while drilling, preventing material buildup that would obscure the fastener opening.
Solution Approach 2:
The alternating sharp and relieved edges create a periodic cutting action as the drill rotates. The sharp edges cut material while the relieved edges allow chip evacuation and periodic clearing of the hole, creating a rhythm of cutting and cleaning that maintains opening visibility throughout the drilling process.
2Productivity
If continuous cutting edges are used on a drill bit, then material removal is efficient, but material buildup obscures the fastener opening
Solution Approach 1:
Different portions of the drill bit circumference have different properties: some edges are sharp for aggressive material removal, while alternating edges are relieved for chip evacuation. This local variation in edge quality allows the drill to simultaneously maintain high cutting efficiency while periodically clearing the hole to prevent obscuration.
Solution Approach 2:
The relieved edges, which might seem to reduce overall cutting capability, actually serve a beneficial function by facilitating chip evacuation and preventing material buildup. The apparent loss of cutting continuity is converted into a benefit that maintains fastener opening visibility and prevents clogging.
3Manufacturing precision
If drill bits are designed to clean-out holes, then fastener openings remain visible, but the drill bit design becomes more complex
Solution Approach 1:
The cleaning function is merged with the primary drilling function by integrating relieved edges into the same drill bit body that performs material removal. Rather than requiring separate cleaning operations or complex auxiliary mechanisms, the alternating edge design combines cutting and cleaning actions into a single unified tool.
Solution Approach 2:
Instead of adding complex cleaning mechanisms to a standard drill bit, the design inverts the approach by making the cutting edges themselves responsible for cleaning through their alternating sharp and relieved configuration. The structure that normally would be considered simple (a solid drill bit) is inverted to create the stepped alternating edge pattern that provides self-cleaning capability.
Data Source
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Figure 5A~6B
AI summary
A drill bit for use with construction using cross laminated timbers (CLT) is provided. The bit has both sharpened and dull portions of the cutting element of the bit, so that it can clean- out an opening in the CLT that has been partially obscured by shifts in the laminated constituents of the CLT, without elongating or otherwise changing the shape of the fastener opening. The use of the bit is made at the construction site in fastener openings previously made and otherwise obscured, thereby allowing the quick assembly and construction of a structure made of CLT.