| 摘要 |
<p>Tubular bit for drilling relatively long narrow holes in soft materials (such as uncured rubbers) features helical grooves on its outer face. Holes at intervals in the base of the grooves communicate with the interior of the bit. Suitable for perforating lightly vulcanised rubbers, (e.g. 20-30 Shore hardness) without local binding or overheating. Pref. the bit is mounted on the end of a solid rotary mandrel having a bevelled lip level with a slot in the wall of the bit to release swarf etc. Esp. suitable for drilling transverse holes in segments of solid rubber tyres to increase flexibility. The superficial grooves allow a liq. lubricant/coolant to be circulated between the surface of the bit and the wall of the drilled hole. The liquid is evacuated via the core of the bit, after passing through the holes. Tool life may be extensive, i.e. resharpening may only be necessary once per day, after drilling about 2000 holes.</p> |
