Rotatable Tool Centering Pin Geometry for Axial Locking
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Solution Overview
Problem
Existing rotatable tools with loose tops face challenges in achieving precise centering and easy mounting/dismounting without compromising manufacturing precision, and in resisting axial forces during drilling operations.
Innovation Solution
The design incorporates a centering pin with diametrically opposed surfaces that form a contact surface extending tangentially between boundary generatrices, transforming into clearance surfaces, ensuring accurate centering and axial locking of the loose top, allowing for simple mounting and dismounting, and resisting negative axial forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a centering pin with cross-sectional area equal to or greater than the center hole is used to achieve precise centering, then manufacturing precision is improved, but mounting and dismounting becomes difficult and time-consuming
Solution Approach 1:
The centering pin is designed with non-uniform cross-sectional area along its length. The upper portion has a larger cross-sectional area that provides precise centering when engaged with the center hole, while the lower portion has a reduced cross-sectional area that allows easy insertion and removal. This local variation in geometry resolves the contradiction between precision and ease of operation.
Solution Approach 2:
The centering pin is functionally segmented into two distinct zones: an upper centering zone with larger cross-section for precision alignment, and a lower insertion zone with reduced cross-section for easy mounting/dismounting. This segmentation allows each portion to fulfill its specific function without compromising the other.
2Ease of operation
If a simple cylindrical centering pin is used to facilitate easy mounting and dismounting, then ease of operation is improved, but centering precision and resistance to axial forces deteriorates
Solution Approach 1:
The centering pin incorporates local geometric variations where specific portions have enlarged cross-sectional areas to provide precise centering and force resistance, while other portions maintain reduced dimensions for ease of insertion. This localized enhancement resolves the contradiction without compromising overall simplicity.
3Ease of operation
If the centering pin cross-sectional area is reduced to enable easy insertion, then ease of operation is improved, but the ability to resist negative axial forces deteriorates
Solution Approach 1:
The centering pin is designed with strategically placed sections of larger cross-sectional area at the upper portion that bear the axial forces during operation, while the lower portion maintains a reduced cross-section that facilitates easy insertion into the workpiece. This local differentiation resolves the contradiction between insertion ease and force resistance.
Solution Approach 2:
The pin is functionally segmented into a force-bearing upper section with larger cross-section and an insertion-friendly lower section with reduced cross-section, allowing each segment to optimize its performance for its specific function.
Data Source
AI summary
A rotatable tool for chip removing machining, including a basic body having front and rear ends between which a first center axis (C1) extends around which the basic body is rotatable, and a loose top having front and rear ends between which a second center axis (C2) extends. The front end of the basic body includes a jaw which is delimited by two torque-transferring drivers and an intermediate bottom in which a part of the loose top is receivable, and a center hole that mouths in the bottom of the jaw and has a hole wall which extends axially inside the basic body and in which a threaded hole mouths for a screw to co-operate with a centering pin that protrudes axially rearward from the loose top, the centering pin being insertable into the center hole. The centering pin has a cross-sectional area that is less than a cross-sectional area of the center hole. The centering pin includes two diametrically opposed surfaces, a first one of the surfaces forming a contact surface that extends tangentially between two axially running boundary generatrices which are situated along an imaginary circumscribed circle (S1), the center of which coincides with the center axis (C2) of the loose top, and between which an arc angle (α) is less than 180°. The contact surface, via the boundary generatrices, transforms into a second one of the surfaces that is spaced-apart inwardly from the circumscribed circle (S1).