When hard turning reaches its limits
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With GrindLine, EWS bridges the gap between turning and grinding: Small internal fits that cannot be properly finished using hard turning can be ground directly on the turning or turning-milling center without the need to re-clamp the workpiece.
Components with small, precise internal fits present particularly demanding challenges in development and manufacturing—for example, in tool and fixture construction, valve and fluid technology, or in precision components for machine and drive engineering. Conventional hard turning, as an established finishing process, can reach its limits—particularly with small internal diameters—depending on the material, geometry, tolerance, and quality requirements. The smaller the bore, the smaller and more delicate the internal tool must be. Tool wear, the resulting tool life, and fundamental process stability also prove to be relevant economic factors, as they directly impact unit costs. In these cases, finish grinding proves to be a proven and reliable alternative. However, conventional processes also exhibit noticeable limitations here, both in terms of quality and cost-effectiveness.
Polishing finish: When one more step is one step too many
Traditionally, the grinding process takes place on a separate grinding machine. In practice, this means that the desired component is machined on the lathe, then removed, clamped into the grinding machine, and—after the internal fit has been ground—further machined as needed. Changing machines not only represents an additional manual step—and thus raises questions of cost-effectiveness—but also poses fundamental quality risks: Re-clamping increases the risk of positional and concentricity errors, which are particularly critical for tight fits.
GrindLine: A proven method reimagined
With the new GrindLine, EWS—the expert in the development, manufacture, and distribution of high-precision tool holders for lathes and milling machines, tool carrier systems, and accessories—offers an alternative to both hard turning (which has limited applicability) and the conventional use of grinding on a separate grinding machine.
GrindLine is a powered toolholder with a high-speed spindle for finish grinding directly on the lathe or turning-milling center.
This not only eliminates the critical need for re-clamping and the associated risks—since the position of the ground internal fit remains referenced to the already machined geometry—but also optimizes the entire manufacturing process in favor of production quality and cost-effectiveness.
The actual technical highlight, however, is the GrindLine’s drive system, which operates purely mechanically. It is therefore not simply an electrically powered grinding unit with a cable or an external power supply. The high-speed spindle is mechanically driven via the AGW interface of the tool turret. This not only eliminates the need to change over to a separate grinding unit but also eliminates the need for machine retooling. At the same time, the GrindLine is more compact than generator-driven units and is suitable for a wide range of different machines. Nevertheless, the high-speed spindle with ceramic-hybrid bearings achieves speeds of up to 40,200 min⁻¹ via the integrated gearbox and, when used with small grinding tools, delivers the required cutting speeds.
A solution for the workshop, from the workshop
With EWS.GrindLine, EWS is expanding its EWS.Special Solutions product line to include a new tooling solution for finish grinding small inner diameters. EWS.Special Solutions brings together application-specific tooling solutions for gear cutting, grooving, polygon machining, high-speed thread cutting, and high-speed micro-machining, as well as internal drilling heads.
This development is not the result of straightforward product marketing, but arose as a practical solution for a specific machining task in EWS’s own production. As described, conventional tools and hard turning methods proved technically and economically unsuitable for the tasks of finish machining small inner diameters. This provided the inspiration for developing an alternative method, which was ultimately advanced into the production-ready GrindLine solution.
EWS.GrindLine made its debut at AMB 2026 in Stuttgart. The first variant was presented as an axial BMT55 version. Additional BMT and VDI versions, as well as straight and angled designs, are being evaluated on a project-by-project basis and will be implemented if technically feasible.
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