When selecting a tool for such operations, the diameter and hardness of the workpiece are not the only critical factors. The geometry of the tool tip determines the shape of the machined surface, while the length of the cutting section and the neck determine accessibility to the target area. The HARD series addresses these requirements through specialized tool configurations—for instance, the 2HCB ball-nose end mills and the 2HRE flat-end mills.
2HCB: Ball-nose cutting geometry with diameters starting from 0.06 mm
The 2HCB two-flute end mills are designed for machining pre-hardened and hardened steels with a hardness ranging from 50 to 62 HRC (Rockwell scale). The ball-nose tip enables the machining of surfaces with radii and complex, variable profiles. The size range spans from 0.06 mm to 20 mm in diameter—covering everything from tools for intricate, small-scale features to versions with a 10 mm ball radius.
For any given diameter, various options for overall length and shank configuration are available. For example, a 6 mm diameter end mill can be supplied with an overall length ranging from 60 mm to 150 mm. This flexibility allows for the selection of a tool that ensures proper access to the workpiece surface and accommodates the dimensions of the workholding equipment, all while maintaining the required cutting radius.
The tool is constructed from an ultra-fine-grained tungsten carbide alloy with a grain size of 0.2 μm. A silicon-based PVD coating is applied to enhance the wear resistance of the cutting section. Furthermore, the manufacturer places a strong emphasis on the precision of the cutting edges and the quality of the resulting surface finish.
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2HRE: Short Cutting Edge and Extended Neck
The 2HRE series of two-flute end mills features a flat end, a short cutting edge, and a reduced-diameter neck. This design allows the cutting edges to reach recessed areas while maintaining clearance between the tool's neck and the workpiece walls.
The distinction between these dimensions is well illustrated by the 2HRE 005 140 S04 model: it has a cutter diameter of 0.5 mm, a cutting edge length of 0.5 mm, an effective reach (length) of 14 mm, and a shank diameter of 4 mm. Therefore, when selecting such a tool, it is important to distinguish between the length of the cutting edge and the maximum achievable machining depth.
2HRE end mills are manufactured from a solid carbide grade with a grain size of 0.2 µm and feature a silicon-based PVD coating. The cutting edge geometry includes edge reinforcement to minimize chipping when machining hardened or tempered steels.
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Machining accuracy also depends on the equipment
For the 2HCB series, the manufacturer recommends using machine tools with high rigidity and low vibration levels. When working with a tool diameter of 1 mm or less, the allowable vibration level should be within 5 µm. If the effective length is increased, both the rotational speed and the feed rate must be reduced proportionally—a limitation that should be taken into account when selecting an extended-length version.
JJ Tools has been active in the field of carbide cutting tools since 1997. The company is headquartered in Seoul, with regional branches located in Busan and Cheonan.