Generally, the hole depth is more than 3-5 times of the hole diameter, which is difficult in chip removal and cooling. Twist drill can be used for the hole with small drilling depth. In order to remove the chip smoothly, the iron chip should be straight out into a thin strip and bring out small fragments. At the same time, the coolant is easy to enter. The grinding method of the drill bit can be relatively simple grinding method.
1. Increase the angle of the drill edge to 130-140 degrees to increase the chip thickness and change the direction of chip discharge (the direction of chip discharge is perpendicular to the edge)
2. Grinding the transverse edge to reduce the axial cutting tool, at the same time, the cutting edge near the core produces a break angle to facilitate chip separation.
3. If the drilling diameter is large, the chip separation groove can be ground on one side of the cutting edge to balance the cutting force of the two cutting edges. If the diameter is large, the chip separation groove can be grinded at the two edges.
4. Reverse 1 mm 45 degrees to the outside corner of the edge to reduce wear and improve finish.
5. The rotary speed of drilling is slightly lower, and the feed rate should be larger, so that the chip thickening can be discharged in strips.
6. The nozzle of the coolant should face the hole inward to facilitate the coolant to enter the cutting area,
When the hole to diameter ratio is more than 8 times and the batch is large, it is better to drill on the special deep hole drilling machine, and the effect is very high