CBN tool solutions for hard turning of bearing steel
Bearings are not only an important part of modern machinery and equipment, they are also fixed parts, mainly used to support the rotating body of machinery, in order to reduce the coefficient of friction during its movement and to ensure its rotary accuracy. Bearings are also consumables, in addition to new projects and new machinery products will pull the demand for bearings, mechanical products to increase the amount of ownership and utilization will increase the consumption of bearings.
China's bearing industry has ranked third in the world in terms of the economic scale of the industry, and China needs to change from a large bearing producing country to a strong bearing producing country, one of the key factors is to improve the technology of precision machining bearings, and cutting tools are a very critical part of it.
There are many different types of bearings and their materials are very diverse. The common ones are common bearing steel GCr15, stainless steel 9Cr18, silicon nitride Si3N4 and zirconium oxide ZrO2 and even plastics. Of these, the bearing steel GCr15 material is the most common on the market. Bearings are subjected to extreme pressure and friction during operation, so bearing steel materials are required to have high and uniform hardness and wear resistance, as well as a high elastic limit. This has very strict requirements for the uniformity of the distribution of the chemical composition of the bearing steel, the distribution and content of non-metallic inclusions and the distribution of carbides.
For bearing steel materials the following conditions must be present:
1 high wear resistance
2 high contact fatigue strength
3 High hardness after heat treatment to meet the requirements of the bearing
4 high elastic limit
5 good impact toughness
6 Good dimensional stability
7 Good rust resistance
8 Good processability
The machining of bearing steel has certain process requirements, especially for the hard turning of bearing steel after heat treatment is a challenge. Amongst other things, the dimensional stability and surface quality of the workpiece need to reach a high standard. WSS tools have carried out continuous R&D and technical research on the machining of bearing industry materials, concentrating on the hard turning of bearing steel after heat treatment, using special customised CBN material and edge treatment, the machining results achieve higher dimensional accuracy and stability, and higher tool life, achieving cost reduction and efficiency, both technical and cost effective.
Case 1
| Machining parts | Bearing rewind slots |
| Processing materials | Bearing steel GCr15 |
| Material hardness | HRC60-62 |
| Surface roughness | Ra1.2~2μm |
WSS custom CBN tools compared to an imported brand of CBN tools, still have 12% higher tool life than the competition under the same conditions of higher line speeds, at a more favourable price and significantly lower cost per part machined, with a standardized part surface.
| Tool brands | WSS | Other brands |
| Specification | VBGW160412 | VBGW160412 |
| VC（m/min） | 230m/min | 230m/min |
| f（mm/rev） | 0.2mm/rev | 0.2mm/rev |
| Ap（mm） | 0.4mm | 0.4mm |
| T/L（Longevity） | 112 Pieces | 100 Pieces |
Case 2
| Machining parts | Bearing bores and end faces |
| Processing materials | Bearing steel GCr15 |
| Material hardness | HRC55 |
| Surface roughness | Ra3.2μm |
| Processing methods | Continuous cutting with coolant |
| Diameter | D68mm |
Due to the continuous cutting and the high
dimensional deformation requirements for the part, WSS is machined by adding
coolant. The final WSS tool has a 137.5% increase in machining life over an
imported brand of CBN tool, achieving more stable machining, reducing the
frequency of tool changes and further reducing machining costs.
| Tool brands | WSS | Other brands |
| Specification | CNGA120408 | CNGA120408 |
| VC（m/min） | 150m/min | 150m/min |
| f（mm/rev） | 0.05mm/rev | 0.05mm/rev |
| Ap（mm） | 0.2mm | 0.2mm |
| T/L（Longevity） | 95 Pieces | 40 Pieces |
Case 3
| Machining parts | Bearing bores and end faces |
| Processing materials | Bearing steel GCr15 |
| Material hardness | HRC60 |
| Surface roughness | Ra1.2μm |
| Processing methods | Rough and finish machining |
| Diameter | 45、80mm |
Both roughing and finishing allowances are 0.3mm. To ensure dimensional stability and surface quality of the part, the surface roughness requirement is Ra1.2μm. WSS is compared with an imported brand and under the same parameters, both roughing and finishing can meet the requirements, in line with the competitors, and WSS tools have a clear cost-performance advantage.
| Tool brands | WSS | Other brands |
| Specification | VCGT160404 | VCGT160404 |
| VC（m/min） | 200m/min | 200m/min |
| f（mm/rev） | 0.07mm/rev | 0.07mm/rev |
| Ap（mm） | 0.3mm | 0.3mm |
| T/L（Longevity） | Roughing 20~30Pieces Finishing 70~80Pieces |
Roughing 20~30 Pieces Finishing 70~80 Pieces |
The WSS advantage: better tools for the money
Case 4
| Bearbeitung von Teilen | Ball bearing grooves |
| Processing materials | Bearing steel GCr15 |
| Material hardness | HRC60-64 |
| Surface roughness | Ra0.6μm |
| Diameter | D182mm |
The part to be machined is the ball groove, which requires a higher surface roughness of Ra0.6μm. The linear speed of the machining is very high, and in competition with a CBN tool of an imported brand, the Weiss tool is able to achieve the same life and high surface quality, with obvious advantages in terms of cost performance.
| Tool brands | WSS | Other brands |
| Specification | VCGT160404 | VCGT160404 |
| VC（m/min） | 260m/min | 260m/min |
| f（mm/rev） | 0.07mm/rev | 0.07mm/rev |
| Ap（mm） | 0.03mm | 0.03mm |
| T/L（Longevity） | 40~50 Pieces | 40~50 Pieces |
The WSS advantage: better tools for the money