In the mechanical manufacturing industry, a cylindrical hole having a hole depth exceeding 5 times the aperture is generally referred to as a deep hole. The ratio of the depth of the deep hole to the aperture (L/D) can be generally divided into three types: general deep hole, medium deep hole and special deep hole. (The larger the ratio of ps:L/D, the more difficult it is to process.)
1, L / D > 5, belonging to the general deep hole, often used in drilling or lathe with long twist drill processing.
2, L / D = 20--30, is a medium deep hole, often processed on a lathe.
3, L / D = 30--100, is a special deep hole, must be processed on a deep hole drilling machine or special equipment using deep hole drilling. Deep hole drilling is divided into external chip removal and internal chip removal according to the chip removal method: the outer chip has gun drill, the whole alloy deep hole drill (can be divided into two types: cooling hole and no cooling hole); It is divided into BTA deep hole drill, jet suction drill and DF system deep hole drill.