DEFORM- AND EXHAUST-CONTROL OF CHIP IN DRILLING WITH A CONTINUOUS HIGH FEED RATE TWIST DRILL

s型钻头在中碳钢深孔加工中具有良好的性能。生产SUS304和纯铝的长螺距切屑。然而，在高切削速度或高进给速度下，排屑变差。在纯铝的情况下，由于切屑与钻头之间的粘性增加，切屑变厚，无法排出。在SUS304的情况下，钻头磨损突然增加，然后停止钻孔。其原因是：胶粘性的增加使切屑变厚，进而加剧加工硬化。它增加了对刀刃的伤害。它增加了粘接性和抗排屑的阻力。然后，它大大提高了加工硬化。在这种链式反应机制和切削温度的作用下，刃口磨损迅速消失。理想的情况是，钻槽上涂有针对这些工作材料的低亲和力材料。锡涂层不好。A2011和A2024铝合金切屑难以形成长节距型。当切削温度达到300℃左右时，出现长螺距切屑。以A5056铝合金为例，在160℃左右出现长螺距切屑。当切削温度高于160℃时，切屑变厚，停止钻进。SCM440的钻削机理与S50C基本相同。与常规钻头相比，s型钻头在钻削含碳量多的SUS304时刀具寿命长。在SUS304含碳量少的情况下，附着力影响s型钻头的刀具寿命。在S50C钻井中，常规钻头的刀具磨损受到钻头振动的影响。因此，主切削刃外缘的侧面磨损最大。s型钻头几乎没有振动，所以侧面磨损从外缘向内一点最大。用s型烧结钻头在5000rpm， 0.3mm/rev下钻削50mm S50C时，尽管切削温度很高，但不会出现长螺距切屑。

S-type drill has good performance in deep hole drilling of middle carbon steel. It produces long pitch chip in drilling SUS304 and the pure aluminium. However, the chip exhaust becomes bad at high cutting speed or high feed rate. In case of pure aluminium, chip becomes thick and can not be exhausted due to increase of adhesivity between chip and drill. In case of SUS304, the drill wear increases suddenly and then drilling is stopped. The cause is as follows : Increase of adhesivity makes chip thick, then it increses work hardening. It increases damage to cutting edge. It increases the adhesivity and the resistace against chip exhaust. Then, it increses the work hardening much more. By this chain reacting mechanism and cutting temperature, cutting edge wears rapidly and vanishes. It is desirable that drill flute is coated with low affinity material aganst these work materials. TiN-coating is not good. It is difficult that chip of aluminium alloys of A2011 and A2024 becomes the long pitch type. When cutting temperature becomes about 300℃, the long pitch chip occurs. In case of aluminium alloy of A5056, the long pitch chip occurs at about 160℃. However, chip becomes thick at higher cutting temperature than 160℃, then drilling becomes stop. The drilling mechanism of SCM440 is almost equal to that of S50C.In contrast with conventional drill, S-type drill is long tool life in drilling much carbon content SUS304 . In case of little carbon content SUS304, adhesivity affects the tool life of S-type drill. In drilling S50C, tool wear of conventional drill is affected by oscillation of drill. So, the flank wear of outside edge of main cutting edge becomes maximum. S-type drill hardly oscillate, so the flank wear becomes maximum at a little inside from outside edge.The long pitch chip does not occur in drilling 50mm S50C with S-type sintered drill under 5000rpm, 0.3mm/rev, in spite of high cutting temperature.