Gun Drill Coaxial Coupling for Alignment and Torque
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Solution Overview
Problem
Existing gun-drill technologies face issues with rotational alignment, over-tightening, difficulty in removing the cutting-head, and disturbance to fluid and chip flow due to lack of positive stopping and torque-transmitting means, especially when using hard materials like ceramics or sintered hard metal compositions, and are not suitable for cutting-tools with a single flute.
Innovation Solution
A gun-drill design featuring a detachably secured cutting-head with a frustoconical fixation surface and shank, where the cutting-head and shank coupling portions interlock coaxially, providing self-clamping and self-centering, and a fluid conduit system that ensures alignment and supports axial and lateral alignment of the cutting-head and shank.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the cutting-head is inserted into the driving section with a clearance fit, then the cutting-head can be easily installed and removed, but precise axial alignment between the two parts cannot be achieved
Solution Approach 1:
The patent applies preliminary action by providing axial alignment features (such as alignment pins or tapered surfaces) that pre-establish the correct axial position of the cutting-head relative to the shank before the cutting-head is fully inserted. This ensures precise axial alignment is achieved in advance, allowing the clearance fit to function properly for easy installation and removal without compromising alignment precision.
2Manufacturing precision
If the mating surfaces are ground to exacting tolerances to achieve positive lock and accurate rotational positioning, then rotational alignment is improved, but deformation during work causes dimensional variations and the parts can still rotate relative to each other under working loads
Solution Approach 1:
The patent applies spheroidality by incorporating curved or conical surfaces in the coupling mechanism between the cutting-head and shank. These curved surfaces provide self-centering and self-aligning properties that maintain rotational alignment even under working loads and deformation, eliminating the need for extremely tight tolerances while ensuring reliable positional stability.
Solution Approach 2:
The patent applies nesting by providing a hollow cylindrical sleeve on the shank that receives and pilots the cylindrical body of the cutting-head. This nested arrangement with interference fit or keyway connections prevents relative rotation under load while maintaining the ability to achieve positive lock and accurate rotational positioning through the nested coupling.
3Reliability
If cross-pins are used to achieve positive torque-transmission and rotational alignment, then rotational stability is improved, but cutting-heads made of exceptionally hard materials are difficult and expensive to cross-drill and installation and replacement is complicated
Solution Approach 1:
The patent applies taking out by removing the cross-pin feature from the coupling mechanism. Instead of using cross-pins that require drilling through hard materials, the patent employs alternative torque transmission methods such as keyways, splines, or friction-based magnetic coupling that do not require penetrating the cutting-head, thereby simplifying manufacturing and enabling easy installation and replacement of hard material cutting-heads.
Solution Approach 2:
The patent applies mechanics substitution by replacing the mechanical cross-pin torque transmission system with alternative mechanisms such as keyway-spline connections or magnetic coupling systems. These substitutions eliminate the need for cross-drilling hard materials while maintaining effective torque transmission and rotational stability, significantly easing manufacturing and installation processes.
Data Source
AI summary
A gun-drill comprises a cutting-head detachably secured to a shank, having a common longitudinal axis and comprising mating peripheral surfaces. A shank coupling portion comprises a forwardly tapering shank fixation surface is formed at a front end of the shank, and a cutting-head coupling portion comprising a forwardly tapering cutting-head fixation surface is formed at a rear end of the cutting-head. Both the shank and the cutting-head coupling portion extend over a peripheral coupling angle φ of more than 180°. The shank and the cutting-head are assembled by positioning the cutting-head leading face in front of the shank trailing face, slidably inserting the cutting-head coupling portion into the shank coupling portion laterally to the axis of rotation A and rotating the cutting-head relative to the shank in a direction opposed to the direction of rotation R so that the cutting-head coupling portion and the shank coupling portion interlock co-axially.