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采用普通麻花钻加工小直径的深孔（L/D>10）是很困难的。有一种用特殊铸铁制造的零件,需要加工出一个深为90mm、直径为8.7H8mm的内孔。由于零件材料的可加工性较差,钻头因剧烈磨损而使寿命降低,造成刀具消耗量增加,孔的精度要求也受到了影响, 分析其原因:一是工件材料强度高;二是钻心处横刃处于较大的负前角,大约为-54°左右,横刃过长,切削时呈刮削挤压,且该处切削速度太低,切屑呈碎粉状不易排出,使得钻头的切削刃两侧转角处磨损加剧。为提高钻头的切削性能和加工质量,将普通钻头修改为图示结构,其效果较佳。
It is very difficult to machine a small diameter deep hole (L / D> 10) with an ordinary twist drill. There is a special cast iron parts, need to work out a depth of 90mm, a diameter of 8.7H8mm bore. Due to the poor machinability of the parts and materials, the drill bit has a longer service life due to drastic wear and tear, resulting in increased tool consumption and hole accuracy requirements. The reasons for this are as follows: First, the workpiece material has high strength; second, The cutting edge is at a large negative rake angle of about -54 °, the long chisel edge is scraped and squeezed during cutting, and the cutting speed is too low at this point. The chips are not easily discharged in the form of pulverized powder, so that the cutting edge of the drill bit two Side corner wear increased. In order to improve the cutting performance and processing quality of the drill bit, the ordinary drill bit is modified into the illustrated structure, and the effect is better.