There are three methods for deep hole processing of prototype models: (1) processing deep holes with a set of material cutters; (2) processing a long-shank twist drill on a general-purpose machine tool; (3) using a deep hole drill to process on a special deep hole drilling machine.

1. Machining deep holes with nesting knife.  Deep holes with larger diameters (generally greater than 50mm in diameter) should be processed with a nesting knife.  This method reduces the cutting load, thereby improving productivity and reducing material consumption.  When the diameter of the nesting knife is small, the integral welding type is usually adopted, and when the diameter is larger, the assembly type or the adjustable type can be adopted.  The tool should be equipped with a wear-resistant insert for guiding. The material can be cloth-filled bakelite, cemented carbide, rolling bearing, etc. The cutting edge design should also consider chip separation and chip breaking.  It is also suitable for mass production.

2. The long shank twist drill is processed on a general-purpose machine tool.  To connect a long shank twist drill is to weld a long shank to an ordinary twist drill.  Due to the large axial force during drilling, the two edges of the drill are not easy to grind symmetrically, the quality of the chisel edge of the drill is not easy to guarantee, and the rigidity of the tool bar is poor, so vibration is prone to occur during processing, and the center line of the hole is prone to deflection.  The chip holding space is limited. In order to remove chips and cool the tool, the drill must be withdrawn after processing a certain length (usually 5-10 mm).  For spindles with longer shaft holes, drill holes from both ends.  Therefore, this deep hole processing method is of poor quality, low productivity, and high labor intensity. However, due to its simple manufacturing of tools and the use of general-purpose equipment, it is often used in single-piece and small-batch production.

3. Use deep hole drill to process on special deep hole drilling machine.  The use of deep hole drilling to process deep holes better solves the problems of tool deviation, tool cooling, chip breaking and chip removal in deep hole processing, and significantly improves processing quality and productivity.  It can process deep holes from 10 to 30.  The deep hole processing machine tool can be a dedicated deep hole drilling machine or an ordinary lathe can be modified.