Wiper-edge CBN inserts use a specially designed cutting edge geometry that forms a smoother machined surface at the same feed rate as a conventional insert. For finish machining of hardened steel above HRC50, this means two things at once: a lower surface roughness — down to Ra 0.8 μm or lower — and a real opportunity to increase the feed rate and shorten machining time per part.
Conventional turning tools mainly rely on the nose radius to generate the machined surface. As the feed rate increases, the cutting marks left by the tool nose become more pronounced, and surface roughness generally increases accordingly.
A wiper edge changes this. Through a special edge design, it effectively increases the length of the cutting edge involved in forming the surface. Under the same feed rate, a wiper-edge CBN insert produces a noticeably flatter, smoother machined surface.
CBN tools are commonly used for finish machining hardened steels above HRC50. After heat treatment, these workpieces are hard and place strict requirements on surface integrity and dimensional accuracy.
A wiper edge reduces pronounced tool marks on the machined surface. For finishing operations that require Ra 0.8 μm or even lower, wiper-edge CBN inserts can reach the target surface roughness more easily when cutting parameters are properly selected.
One of the biggest advantages of a wiper edge is that the feed rate can be increased while still meeting the surface roughness requirement. With a conventional insert, raising the feed rate causes surface roughness to deteriorate quickly, which limits productivity. A wiper edge slows down this negative effect.
So for a fixed surface quality requirement, properly applied wiper-edge CBN inserts can shorten machining time per part and improve production efficiency simply by allowing a higher feed rate.
A wiper edge is not superior to a conventional edge under all conditions. Because it increases the effective contact area between tool and workpiece, cutting forces may rise under certain conditions. The machine tool, tool holder, and workpiece clamping must therefore be sufficiently rigid.
If machine rigidity is poor, the workpiece overhang is long, or clamping is unstable, a wiper edge can instead cause vibration or chatter, harming both surface quality and tool life. Wiper-edge selection must match the actual machining conditions — a larger wiper edge is not automatically better.
Wiper-edge CBN inserts are especially suitable for continuous finishing operations where surface quality and production efficiency are required at the same time, such as:
| Application Area | Typical Workpieces |
|---|---|
| Hardened steel shafts | Finish machining of hardened shaft parts above HRC50 |
| Automotive gears and transmission components | Precision finishing after heat treatment |
| Bearing rings and bearing components | Boring and turning of rings and rolling elements seats |
| Hardened mold components | Finish machining of mold parts after heat treatment |
| High-hardness cast iron components | Turning of high-hardness cast iron parts |
| Brake discs and brake drums | High-efficiency facing of automotive brake components |
| Ra-controlled finishing operations | Any finishing pass with defined Ra targets such as Ra 0.8 μm or Ra 0.4 μm |
For these applications, the right CBN grade and wiper-edge geometry should be selected according to the workpiece material, hardness, machining method, machine rigidity, and target surface roughness.
Choosing a wiper-edge CBN insert should not be based on the insert designation alone. Four factors need to be evaluated together:
Different materials impose different requirements on CBN content, grain structure, and binder system. Hardened steel and high-hardness cast iron, for example, cut very differently and call for matching CBN grades.
Continuous cutting, light interrupted cutting, and heavy interrupted cutting place different demands on the insert. The tool geometry should be selected according to the actual conditions.
If the target is Ra 0.8 μm, Ra 0.4 μm, or lower, the wiper-edge geometry, nose radius, feed rate, and cutting speed must be considered together — rather than relying solely on reducing the feed rate.
Wiper edges demand relatively high rigidity from the machining system. Only when the machine tool, tool holder, and clamping are stable can the wiper edge fully deliver its advantages.
For CBN tools, the insert material determines wear resistance and high-temperature performance, while the tool geometry directly affects cutting forces, surface roughness, and machining efficiency. A wiper edge is not simply an extra edge — it optimizes the nose geometry to balance efficiency, surface quality, and stability.
Our wiper-edge CBN inserts are designed for precisely this balance: finishing hardened steel and other high-hardness materials with low surface roughness and higher feed rates in the same pass. With matched CBN grades, wiper-edge structures, and optimized cutting parameters, stable and efficient finishing is achievable across shafts, gears, bearings, molds, cast iron parts, and brake components.
If you are evaluating wiper-edge CBN inserts for a specific workpiece, our technical team can help you select the right grade and geometry based on your material, hardness, machine conditions, and surface finish targets.
A wiper edge is a specially designed cutting edge geometry that effectively lengthens the edge involved in surface formation. It wipes the machined surface a second time, producing a smoother finish at the same feed rate as a conventional nose radius.
Yes. For hardened steel above HRC50, wiper-edge CBN inserts can reach Ra 0.8 μm or even lower with properly selected cutting parameters, and can also support Ra 0.4 μm targets when geometry, nose radius, feed rate, and cutting speed are matched.
It can. A wiper edge increases the effective contact area between tool and workpiece, so cutting forces may rise under certain conditions. Sufficient rigidity of the machine tool, tool holder, and clamping is required; otherwise vibration or chatter may occur.
Continuous finishing operations that demand both surface quality and efficiency: hardened steel shafts, automotive gears and transmission parts, bearing rings, hardened mold components, high-hardness cast iron parts, and brake discs and drums.
