Drill machining of forged steel

High forces must be applied to machine parts from forged steel. This material also tends to form longer pieces of swarf that are difficult to remove. For these reasons, Höhnhart, Austria-based Ferdinand Bernhofer GmbH machines forged steel workpieces on a two-spindle machine from Schwäbische Werkzeugmaschinen GmbH (SW).

Bernhofer began ambitiously expanding its range of services several years ago, with the expansion of installation-ready machining to a standard service being a top priority. Bernhofer therefore set out to find a manufacturer of suitable machine tools. Above all, the machine tools had to be sturdy and powerful enough to handle the three-shift machining of forged parts. The components being machined are combined in groups so the systems can be changed over or re-tooled as quickly and smoothly as possible. Another criterion was the most extensive automation possible, in order to conserve resources through 24/7 operation.

The first project was a family of parts with six variants made of quenched and tempered steel for motorcycle frames. Project goals included fully automatic machining and product swaps with no change-over. The BA 322 (a horizontal machining centre from SW with two synchronous spindles), was chosen to accomplish these ambitions.

“The mutual trust we have built on this foundation led us to choose SW again for the next project,” says managing director Ferdinand Bernhofer.

To explain, the new project involved machining particularly large drawbar eyes made from different variants of 42CrMo4. The task was made more difficult by the relatively large number of holes and fits that had to be machined, and was further complicated by the need for cooling lubricant to drill the holes. SW’s milling machine type BA 722 was purchased for this purpose. The larger machining centre, also with two spindles, was needed mainly because considerably greater quantities were to be removed through machining than for the motorcycle parts. Machining must remove up to 3 kg of material from each drawbar eye, which may weigh up to 18 kg, depending on the variant.

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