End-Mill Screw Rib Layout for Lower Insertion Torque
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Solution Overview
Problem
Existing self-tapping screws face high insertion torque when used in materials like wood or plastic, which can lead to increased screwing resistance and difficulty in cutting effective threads.
Innovation Solution
The screw design features a constant thread pitch along the shaft with varying pitch milling ribs arranged helically, where the first set of ribs is opposite to the thread direction and the second set is in the same direction, with pitches significantly larger than the thread pitch, to effectively separate and straighten wood fibers, reducing insertion torque without compromising holding values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional self-tapping screw with a single set of milling ribs is used, then the screw structure is simple, but the insertion torque is high and wood fibers are not effectively separated
Solution Approach 1:
The milling section is divided into two distinct sets of milling ribs: a first set with a first pitch and a second set with a second pitch. This segmentation allows each set to perform different functions in the fiber separation process, reducing insertion torque through more effective milling action without requiring a single complex rib structure
Solution Approach 2:
Different regions of the milling section have different rib configurations. The first set of milling ribs has a first pitch optimized for initial fiber separation, while the second set has a second pitch optimized for further separation and straightening. This local differentiation of properties enhances overall milling effectiveness while maintaining structural clarity
2Adaptability or versatility
If the thread pitch varies along the screw shaft, then the screw can adapt to different material densities, but the thread engagement becomes less predictable and holding values may be reduced
Solution Approach 1:
The screw design applies different pitch characteristics to different functional regions: the screw thread has a variable pitch along the shaft to adapt to different material densities during insertion, while the milling ribs have constant pitches in their respective sets to provide predictable and reliable fiber separation. This localized differentiation allows each region to optimize its performance for its specific function
3Device complexity
If the milling ribs have the same pitch as the screw thread, then the structure is simplified, but the milling effect is reduced and wood fibers are not effectively separated
Solution Approach 1:
The milling ribs are segmented into two sets with different pitches that are distinct from the screw thread pitch. This segmentation creates a specialized milling action that differs from the threading action, allowing effective fiber separation without requiring the milling ribs to match the thread pitch configuration
Solution Approach 2:
Instead of making the milling ribs match the thread pitch (conventional approach), the invention inverts this relationship by using pitches that are specifically different from the thread pitch. This inversion creates a more effective milling action that better separates wood fibers while the threads subsequently provide the holding function
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design significantly reduces insertion torque by enhancing the milling effect, allowing better separation and removal of wood fibers, thereby easing the screwing process while maintaining holding strength.
Implementation Method 1
The interaction of the milling ribs thus achieves a better milling result, which reduces the screwing torque. The wood fibers are at very different angles to the longitudinal axis of the screw. Therefore, only a portion of the relevant wood fibers is cut by the milling ribs of the front set
Implementation Method 2
another portion of the wood fibers is simply pushed against the hole wall, i.e., the wall of the screw hole. Due to the different pitch of the rear milling ribs, at least some of these remaining wood fibers are straightened up again and also separated
Data Source
Figure 1~2
AI summary
The invention relates to a screw (1) having an end mill (7). In order to reduce a screw-in resistance of the screw (1), the invention proposes that the end mill (7) have two successively arranged sets (9, 11) of milling ribs (10, 12), of which the front milling ribs (10) are in the opposite direction to and the rear milling ribs (12) are in the same direction as the screw thread (8). Both sets (9, 11) of milling ribs (10, 12) have, in terms of magnitude, a greater pitch than the screw thread (8) and the milling ribs (10, 12) transition into one another in a V shape.