Base Plate Screw Hole Geometry to Prevent Tapping Burrs
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional base plates in disk drive devices experience burr formation during screw hole tapping, leading to assembly precision issues and rattling due to stress application and protrusion of threaded parts.
Innovation Solution
A base plate design featuring a screw hole with an inclined part and a column body, where the inclined part has a decreasing inner diameter and is inclined at an angle of 25° to 35°, reducing stress and burr formation, and ensuring the burr does not protrude below the bottom wall.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If tapping is performed on a conventional screw hole, then a threaded part is formed, but a burr protrudes from the lower end of the screw hole causing assembly precision issues
Solution Approach 1:
The screw hole is pre-formed with a rounded bottom shape before tapping. This preliminary action prevents the rolling tool from contacting the inner circumferential surface at sharp angles during tapping, thereby preventing burr formation at the lower end of the screw hole while still allowing threaded part formation
Solution Approach 2:
The shape parameter of the screw hole bottom is changed from a sharp or flat bottom to a rounded bottom with a specific radius of curvature. This parameter change reduces stress concentration during tapping and prevents the rolling tool from raising the inner circumferential surface, thereby eliminating burr formation
2Reliability
If tapping is performed on a conventional screw hole, then a threaded part is formed, but stress is applied to the lower end circumferential edge causing the inner circumferential surface to raise and form a burr
Solution Approach 1:
The radius of curvature at the bottom of the screw hole is optimized to reduce stress concentration during tapping. This parameter change prevents excessive stress from raising the inner circumferential surface at the lower end, thereby preventing burr formation while maintaining component stability
Solution Approach 2:
The rounded bottom shape is prepared in advance before tapping, creating a stress-distributing geometry that prevents stress concentration at the lower end circumferential edge during the tapping process, thereby preventing burr formation
3Stability of the object's composition
If a burr protrudes from the lower end of the bottom wall, then the base plate may rattle when placed on a work table, but assembly precision of components mounted on the base plate decreases
Solution Approach 1:
The screw hole is pre-formed with a rounded bottom shape before tapping. This preliminary action prevents burr formation that would cause rattling, thereby maintaining both base plate stability and assembly precision
Solution Approach 2:
The radius of curvature at the screw hole bottom is optimized to prevent burr formation. This parameter change eliminates the source of rattling while maintaining assembly precision by preventing burr-induced misalignment
Data Source
AI summary
A base plate includes a bottom wall and a peripheral wall. The peripheral wall extends from the bottom wall to an axially upper side. The bottom wall includes a screw hole recessed from a peripheral edge of a lower end surface of the bottom wall to the axially upper side. The screw hole includes an inclined part and a column body. The inclined part is defined to have an inner diameter that decreases from a lower end toward the axially upper side. The column body extends from an upper end of the inclined part to the axially upper side and is defined with a threaded part. In a cross section including a center line that passes through a center of the column body in an axial direction, the inclined part is inclined at an inclination angle of 25° or more and 35° or less with respect to the center line.