Internal chip removal deep hole drilling means that the chips are discharged from the inside of the drill rod without contacting the machined surface of the workpiece during operation, which can obtain better machined surface quality. The BTA deep hole drill consists of a drill bit and a drill rod, which are connected together by a multi-head rectangular thread. The cutting fluid enters the cutting area from the gap between the workpiece hole wall and the outer surface of the drill rod under high pressure to cool and lubricate the cutting part of the drill bit, and flushes the chips into the drill rod through the chip removal hole at the front end of the drill bit and discharges them backwards. The cross section of the drill rod is tubular and has good rigidity, so the cutting efficiency is higher than that of external chip removal. Internal chip removal deep hole drills are mainly used to process deep holes with d=18~185mm and an aspect ratio of less than 100. Usually, the diameter of 18.5~65mm is made into a welded type, while the diameter greater than 65mm is made into an indexable type.