Purpose of test
A cBN radius end mill was tested for slot machining in hard materials, which is a difficult process with conventional carbide end mills due to their machining inefficiency and limited tool life.
| Test environment | |
| Machine | YBM-640V |
| Work material | SLD(HRC60) |
| Cutting fluid | Oil mist |
| Tool used | cBN radius end mill (φ1 × R 0.1 × 6 (effective length)), manufactured by Kyowa |
Test description
Cut slots 1 mm wide by 6 mm deep in a block measuring 80×60×30 mm, followed by visual evaluation at 200× magnification.
| Machining conditions | |
| Spindle rotational frequency | ：18,000rpm（56.5m/min） |
| Feed speed | ：500mm/min（0.013mm/tooth） |
| Cutting | :10 μm × 600 strokes per slot |
| Cutting length | :80 mm × 600 strokes = 48000 mm (48 m) per slot |
| Machining time | :1 h 42 min per slot |
Test results
A cBN radius end mill was able to cut ten slots 1 mm wide by 6 mm deep by 80 mm long in a hard material. However, beginning with the fifth slot, traces of wear or chipping can be seen at the corners. The total cutting length attempted in this test was 48 mm × 10 slots = 480 mm, but a practical length is 48 mm × 4 slots = 192 mm. (Only one slot can be cut with a carbide end mill.) However, increasing the cutting speed (1.5 to 2 times faster) would provide more favorable conditions.
| Table 1 Cutting conditions | |
| Workpiece | Pyrex |
| Tool | cBN, R0.2mm |
| Feed rate | 0.24mm/min |
| Axial depth of cut | 20μm |
| Rotation rate | 20000rpm, 40000rpm, 60000rpm |
| Effects of rotational frequency and cutting oil on machined surfaces | ||
| Rotational frequency | Machined edge | Machined surface |
| 20000rpm |  |
 |
| 40000rpm |  |
 |
| 60000rpm |  |
|
