Method of forming a high performance thread forming screw
US8172692B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jul 28, 2009 |
| Grant date | May 8, 2012 |
| Priority date | — |
| Expiry date | Apr 29, 2030 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY02P10/25
- WIPO fieldMechanical elements
- WIPO sectorMechanical engineering
Abstract
A thread forming screw having a minimum surface hardness of HRC 56. The screw can form threads in a workpiece having a surface hardness which exceeds HRC 23. A method of surface hardening a screw includes carbon enriching the screw to at least a 0.48 carbon level, and then quenching the screw. Then, the screw is tempered such that the surface hardness does not exceed the core hardness by more than 3 Rockwell C points, and both the surface and core are at a Rockwell C33-C39 hardness. Subsequently, the point is induction hardened, and the screw is quenched again. The screw is again tempered such that the lead threads and the first 3-4 full threads are at a Rockwell C56 minimum hardness, preferably to a depth of at least 0.008 inches, and the core of the fastener is at Rockwell C33-C39 hardness. Finally, a finish is applied.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.