Mass production of wheel bolts made of chromium-molybdenum alloyed steel 42CrMo4
Wheel bolts of strength class 10.9 (tensile strength approx. 1000 MPa) are made of alloy steel, which is given high strength and hardness through special heat treatment. The steel used contains the alloying elements chromium, molybdenum and manganese in particular. They improve the corrosion resistance and mechanical properties, but also increase the demands on the production tools. Vehicle wheels are securely connected to the hub using wheel bolts. The knurled collar ensures that the bolts do not rotate when the wheels are fitted or removed.
RAA-Knurling profile made with IFANGER Knurling roll RDAA-200806-00-1.0-HSS
The challenges
The production of RAA knurling profiles by deformation on wheel bolts made of 42CrMo4 with a diameter of 14 mm and knurl pitches of 0.8 to 1.2 mm places high demands on the knurling tools. Knurling wheels made of powder metallurgical material tend to wear prematurely, which impairs the quality of the knurls.
Consequences
The rapid wear of the knurling tools results, for example, in chipped teeth, uneven and visually unattractive knurls, increased tool and set-up costs and breakage of the knurling wheels .
Solutions
Knurling rollers made from extruded HSS (high-performance steel) are superior to knurling rollers made from powder metallurgy, particularly when knurling tough materials. The specific material properties make HSS the ideal material for knurling tools - wherever precision, durability and cost-effectiveness are required. HSS is characterized by its high temperature resistance and retains its hardness up to approx. 600 °C, which enables it to be used at high cutting speeds. In addition, extruded HSS is less susceptible to breakage than powder metallurgical HSS or carbide. IFANGER Swiss-Knurl knurling wheels are surface-ground on both sides and the bores are precision honed - for maximum axial and radial run-out accuracy. The result is clean, dimensionally accurate and visually perfect knurls. For demanding applications, we offer our HSS knurling wheels with an additional coating as an option - for even greater wear resistance and a longer service life.
Application example
Wheel bolt (grade 10.9)
Material: 42CrMo4 (1.7225)
Knurl shape: DIN82-RAA-1.0
Knurl pitch: 1 mm
Knurl diameter: 14 mm
Knurl width: 8 mm
Thread: M12
IFANGER knurling wheel used: RDAA-200806-00-1.0-HSS
Users confirm that the IFANGER knurling rollers are unique on the market as they are available in many sizes and pitches as standard and offer a long service life even with tough materials.