Blind-Hole Thread Repair Tool With Guided Bottom Thread Engagement
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Solution Overview
Problem
Existing methods are inadequate for repairing damaged threads in blind threaded holes, as traditional tapping cannot reach undamaged threads below a damaged area without enlarging the hole, making it difficult to rethread effectively.
Innovation Solution
A thread repair tool with a shaft featuring concave curved surfaces and corner portions, including threaded areas near the bottom end, allows insertion past a weld and engagement with undamaged threads below, using a gage pin to maintain contact and rethread the damaged area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If traditional tapping is used to repair damaged threads, then the hole can be rethreaded, but the hole must be enlarged which is not feasible for blind holes with damaged surface threads
Solution Approach 1:
The repair tool shaft is segmented into distinct functional zones: a smooth unthreaded portion for navigation past welds and damaged areas, and a threaded portion for engaging undamaged threads. This segmentation allows the tool to perform multiple functions in sequence without requiring hole enlargement.
Solution Approach 2:
The gage pin acts as an intermediary element that maintains continuous contact with the shaft's curved surfaces during rotation. This ensures proper alignment and prevents the shaft from jumping out of the hole while threading, enabling reliable repair without enlarging the hole.
2Ease of repair
If a threaded shaft is inserted to reach undamaged threads, then rethreading can be achieved, but the shaft may jump out of the hole during rotation
Solution Approach 1:
The shaft incorporates curved surfaces with specific radii that match the gage pin geometry. This curved interface creates continuous point contact that guides the shaft during rotation, preventing it from jumping out of the hole while maintaining stable engagement with the undamaged threads.
Solution Approach 2:
The gage pin serves as a mediator between the shaft and the hole walls, maintaining continuous contact through the curved surfaces. This intermediary element provides lateral support and guidance during the threading operation, ensuring the shaft remains positioned correctly throughout rotation.
3Ease of repair
If the shaft has threaded area extending from top to bottom, then threading can be performed, but it cannot bypass the damaged top portion to engage undamaged threads below
Solution Approach 1:
The shaft is divided into functionally distinct segments: an unthreaded smooth portion that navigates past damaged surface threads and welds, and a threaded portion that engages only with undamaged threads at the bottom. This segmentation enables the tool to bypass damaged areas while maintaining adequate threaded engagement length.
Solution Approach 2:
Different portions of the shaft have different surface characteristics tailored to specific functions: the upper portion has a smooth unthreaded surface for navigation and alignment, while the lower portion has threaded surfaces for engagement. This local differentiation allows the shaft to perform multiple functions within a compact length.
Data Source
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AI summary
A thread repair tool (10) for rethreading a blind tapped hole having damaged threads above undamaged threads of the hole, including: a shaft (12) having a plurality of curved surfaces (14) that extend from a top end (16) of the shaft (12) to a bottom end (18) of the shaft (12), the plurality of curved surfaces (14) being concave with respect to an exterior perimeter of the shaft (12); and wherein the shaft (12) has a plurality of corner portions (20), each one of the plurality of corner portions (20) being located in between two of the plurality of curved surfaces (14), a first pair of the plurality of corner portions (20) extending from the top end (16) to the bottom end (18), and a second pair of the plurality of corner portions (20) having a threaded area (22) proximate to the bottom end (18), the first pair of the plurality of corner portions (20) being adjacent to each other and the second pair of the plurality of corner portions (20) being adjacent to each other.