Einbringen von Bohrungen und Gewinden kleiner Durchmesser in randschichtgehärtete Werkstücke

FKM 1996
Booklet No. 214
Project No. 177

Abstract:

The complete machining of components in a single clamping operation on a machine tool will become increasingly important in the future. This also applies to hardened workpieces. In addition to drilling holes in hardened and highly tempered workpieces after heat treatment, it is therefore also necessary to insert threads into these components. After the drilling of surface-hardened materials was investigated in the AiF project 8081 Drilling of hardened steels and can be used reliably, the problems of step drilling, complex drilling, chamfering and threading were investigated as part of this continuation project. The introduction of threads into surface-hardened components poses particular manufacturing problems, which are caused on the one hand by the existing hardness of the workpiece and on the other hand by the hardness gradient towards the material core. Tests with carbide tools have not been very successful, i.e. the tools used fail uncontrollably due to breakage. By using an extended lead, a twisted cutting edge area in conjunction with an HSS cutting material with a high Co content, tool life of around 30 threads could be achieved. Economical tool life can therefore only be achieved with the cutting materials currently available for threading surface-hardened steels if the thread insertion takes place exclusively in the unhardened material or in the transition area by redesigning the chamfer geometry. If new tool geometries with high hardness, toughness and bending strength can be produced as part of further developments in the field of ultra-fine grain carbides or cermets, these offer great potential for hard threading and should be used for threading in case-hardened components. Overall, the investigations into drilling, chamfering and threading have shown that the machining of case-hardened workpieces can be carried out reliably, taking into account the boundary conditions. With the knowledge gained, existing production processes can be redesigned or new ones can be fundamentally shortened by carrying out hardening after pre-machining and then drilling and tapping. By equipping lathes with driven tools, complete machining in the hardened material state is possible. Scope of report:
73 p., 31 ill., 116 lit. Start of work:
01.12.1992 End of work:
31. 12. 1994 Funding body:
BMWi / AiF-Nr. 9168 Research center:
Institute for Production Engineering and Cutting Machine Tools, University of Hanover
Institute Director:
Prof. Dr.-lng. Dr.-lng. E.h. H. K. Tönshoff Processors and authors: Dr.-lng. H.-G. Wobker Dipl. -lng. W. Spintig Chairman of the expert group:
R. Ankenbrand, Flender AG, Bocholt Chairman of the advisory board:
Prof. Dr.-lng. H. Kipphan Heidelberger Druckmaschinen AG, Heidelberg