DEFORM-AND EXHAUST-CONTROLL OF CHIP IN DRILLING WITH A NEW TYPE TWIST DRILL II

在连续进给条件下，麻花钻深孔钻削时，为了排屑，必须使钻槽和漂移孔将其变形为直径较小的锥形螺旋型或成螺距等于螺距的长螺距螺旋型切屑。一种新型麻花钻每边都有两个刃口。每个切割刃独立切割工作材料。每个切削刃所产生的芯片并不完美统一。第二主切削刃所述的芯片附着在第一主切削刃所述的芯片上，第一主切削刃即为主芯片。这是控制切屑变形和排屑的基础。由于第一主切削刃的斜角较大，因此锥形螺旋型切屑的节距较长，在深孔钻孔中，由凹槽和钻孔控制其为长节距型。长螺距螺旋型切屑的切削比小于锥形螺旋型切屑的切削比。特别是在外缘，它是非常小的。在凹槽和钻孔对切屑的弯矩和摩擦力的共同作用下，切削区域产生压缩应力。尤其是它的外缘很大。这使得在工作材料塑性良好的情况下，剪切角较小，从而产生长节距螺旋型切屑。第二主刃口的作用也很大。与0度前角钻头相比，第2主切削刃为4度前角的钻头在钻孔过程中较早产生长螺距螺旋型切屑。钻削S50C时，在各种切削条件下，当切屑形态转变为长节距型时，切削温度在400℃左右。在此温度下，其塑性变大。因此，芯片不断裂，并改变为长螺距型。长节距型切屑的不稳定产生使径向切削力产生振动。切屑形态的变化与切削力特性之间的关系尚不清楚。少

In order to exhaust chip in deep hole drilling with a twist drill under continuous feed, it is necessary that the drill flute and the driffed hole deform it to the smaller diameter conical helix type or to the long pitch helix type chip whose pitch is equal to the flute pitch.A new type twist drill has two cutting edges on each side. Each cutting edge cuts work material independently. The chip generated by each cutting edge are not perfectly unified. The chip by the 2nd main cutting edge is attached to the chip generated by the 1st main cutting, edge which is main chip. This is the basis to the deform and exhaust controll of chip. As the 1st main cutting edge has large oblique angle, so the conical helix type chip has longer pitch, and the flute and the drilled hole controll it to the long pitch type in deep hole drilling. The cutting ratio of the long pitch helix type chip is smaller than that of the conical helix type chip. Especially, at the outside edge it is very small. Under the … More action of the bending moment and the frictional force agaist chip by the flute and the drilled hole, the compressed stress occurs at the cutting region. Especially it is large at the outside edge. This makes the shearing angle small under good plasticity of work material and then the long pitch helix type chip occurs. The effect of 2nd main cutting edge is also large. The drill with the 2nd main cutting edge of 4 degree rake angle produces the long pitch helix type chip at earlier stage in drilling than in case of the 0 degree rake angle drill.The cutting temperature is about 400ﾟC at rake face when the chip form chages to the long pitch type under various cutting conditions in drilling S50C.Its plasticity becomes large at this temperature. So, the chip does not fracture and changes to the long pitch type.Unstable generation of the long pitch type chip makes the radial cutting force vibratory. The relation between change of chip form and the characteristics of cutting force is not clear. Less