Success stories

ZF Lenksysteme

A new servo drive calls for new screws.


Perfectly coordinated

Our expertise formed the basis for the efficient development of the new fastener.

In the development of the special screw for ZF Lenksysteme, we took charge of the project and came up with a winning solution.

Initial situation


High demands

A car without power steering? For most people nowadays it's inconceivable. That is why car manufacturers around the world rely on technology from ZF Lenksysteme (now Robert Bosch Automotive Steering). We became involved when, as part of a large-scale product optimisation initiative, a number of different ranges were combined to form a new, universal range. The design of the servo drive was optimised during the course of this process, leaving it with three rather than four screws. The problem was that the forces acting on the individual screws were too high for the existing special screws (M6 x 144 with hexalobular drive). A modification was urgently required. Since optimising a special screw as part of an ongoing development process is a particularly complex undertaking, ZF Lenksysteme called on Böllhoff's expertise to help. We supported the company in the process and acted as an intermediary between our customer and screw manufacturers.

Customer profile






Collaborative development of a special screw (M6 x 140)

Central to the process was the complex coordination between all the parties involved: car makers, ZF Lenksysteme, screw manufacturers and – as the service provider in the middle – ourselves. We analysed the development concepts and data from car makers and from ZF Lenksysteme and defined all the parameters: from the head diameter and the material to the production processes. We then passed on this data to the screw manufacturers. The prototypes of the modified special screws were then tested in our accredited laboratory. At each stage of the development process the engineers were given the prototypes with full documentation, in accordance with ZF Lenksysteme's quality guidelines for suppliers – extensive lab reports, including the results of salt spray tests, hardness tests, preload force analyses and overtorque tests. In addition, we supported the engineers at ZF Lenksysteme by taking charge of the development of the fastener.
Despite the complexity of the car makers' requirements for the special screw, arising from the very tight tolerances between length and straightness, we were able to deliver a thoroughly satisfactory solution in the form of the M6 x 140 special screw with hexalobular drive.



Lower costs through component optimisation

Lower costs. Greater safety. In extensive series of tests we were able to demonstrate the advantages of the new M6 x 140 special screw with hexalobular drive and dispel any concerns about its loading capacity. In spite of its shorter thread. By taking charge of the development of the fastener, we were able to save the engineers at ZF Lenksysteme a good deal of time. In addition, optimising the component (by dispensing with a collet) and modifying the special screw in a cost-effective way has brought about clear cost savings.

Customer benefits

  • Extensive laboratory tests
  • Significant cost savings through component optimisation
  • Provision of technical expertise
  • Management of suppliers


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