en.Wedoany.com Reported - German tool holder manufacturer Gewefa, in collaboration with cutting tool company Wunschmann, completed a slot milling test at Gewefa's facility in Burladingen. The test used a Wunschmann trochoidal milling cutter paired with a Gewefa SK40 Plan hydraulic expansion chuck on an AXA machining center to machine nitrided steel workpieces, ultimately achieving optimal results in tool life, dimensional accuracy, and surface quality.

All equipment suppliers involved in the project are from Germany. Gewefa products are exclusively sold in the UK and Ireland through Nydaloxe Precision, based in Wiltshire.

The workpiece material machined in this test was nitrided steel (34CrAlNi7), a typical difficult-to-machine material whose high surface hardness and wear resistance make it commonly used in components such as high-speed spindles, shafts, gauges, precision measuring equipment, and cams. The machining task was to mill a slot measuring 1160mm in length, 20mm in width, and 6.5mm in depth into this material.

Stephan Wunschmann, Managing Director of Wunschmann, stated that with its solid carbide 175 ER trochoidal milling cutter featuring a corner radius, the company possesses the ideal cutting tool for slot milling in this demanding material. The cutter offers cutting lengths from 18 to 70mm, corner radii from 0.25 to 0.5mm, and is equipped with a high-performance HE-S PVD (Physical Vapor Deposition) coating specifically designed for hard machining, providing high-temperature resistance and oxidation resistance. The tool features five large polished chip flutes and a robust core structure, with a variable helix angle design that helps suppress vibration and extend tool life.

Norbert Schmid, Sales Manager at Gewefa, pointed out that achieving optimal machining results requires coordinated consideration of all related elements—cutting tool, tool holder, spindle, and machine tool—and this application was a practical example of that approach.

At the Gewefa facility, the trochoidal milling cutter was used on a large AXA five-axis traveling-column universal machining center. The machine has an X-axis travel of 4m and is equipped with a swivel spindle rated at 40kW and 191Nm of torque. The tool is mounted via a tool holder with both face and taper contact to prevent axial movement under heavy radial loads.

The initial test used a 16mm diameter cutter held in a collet chuck with the same face and taper contact. At that time, the cutting speed (Vc) was 80 m/min and the feed rate was 0.16 mm/min. The operators were satisfied with dimensional accuracy and surface quality, but the noise level during slot milling was considerably high. The collet chuck was then replaced with a Gewefa SK40 hydraulic expansion chuck, also featuring a dual-contact spindle interface, and the noise issue was resolved. This tool holder transmits torque and cutting forces through friction and positive locking without slipping.

The improvement in cutting performance is attributed to the higher rigidity provided by the hydraulic expansion dual-contact tool holder, which reduces vibration. This tool holder typically achieves runout accuracy of less than 3µm. Compared to shrink-fit tool holders, hydraulic technology reduces setup time by an average of 75% and requires no shrink-fit equipment, allowing setup to be performed anywhere on the shop floor.

The hydraulic system enables a precise, concentric, and backlash-free connection for the milling cutter. Hydraulic oil is contained within the tool holder cavity, and when system pressure is increased via the adjusting screw, the inner wall applies uniform pressure around the cutter shank, with identical pressure distribution at every point on the circumference. In the dual-contact version, the rigidity and reliability of the hydraulic expansion chuck are further enhanced. Additionally, the lightweight and dynamically superior SK40 swivel spindle head has a lower moment of inertia than the more expensive SK50 spindle head, whereas achieving equivalent machining results with a standard tool holder might require an SK50 spindle head.

Gewefa will attend AMB 2026, the International Exhibition for Metal Working, held from September 15 to 19, 2026, in Stuttgart, at booth 1B84 in Hall 1.