Because deep hole machining is carried out in a closed or semi-closed condition, the drilling status of the NC inserts cannot be directly observed. Therefore, the effective design of the NC tools is essential to the normal operation of the drilling. . In general, the design principles of deep hole drilling should have the following three standards:
1.The cutter tooth specifications adopt standard
The specifications of the cutter teeth are mainly based on the drilling load of the cutter teeth during the entire drilling process, and the drilling load is related to the total width of the cutter teeth. The total width of the cutter teeth should be based on the drilling conditions and The diameter of the drill bit is allocated. The overall width distribution of the cutter teeth should consider 3 standards:
a. Ensure that the eccentric distance e = (0.1 ~ 0.2) d0 of the drill tip, the value of e is related to the material being processed and the diameter of the drill bit, and its size determines the magnitude and direction of the radial combined force of the drill bit. Reasonable eccentricity makes moderate radial force press on the wall of the processed hole, which plays the role of stable drilling, enhanced guidance and improved hole surface quality. At the same time, zero cutting of the drill point is avoided, and the harsh cutting conditions at the drill core are improved;
b. A + C + e + F> d0 / 2 + (1 ~ 2) mm, that is, there must be a certain overlap between the teeth;
c. A + CeF ＞ (1 ~ 3) mm, which can make the cutting radial force always press the guide block, and the guide block is pushed forward against the wall of the machined hole. Straightness.
2.The standard of knife tooth raw materials
The raw materials of the cutter teeth should be selected according to the load and drilling conditions of each tooth. The central tooth is subject to a large axial force, the extrusion friction is severe, and the drilling standards are poor. Therefore, it is necessary to consider the use of YG or YW cemented carbide tools with high bending strength and strong impact resistance; The middle tooth is used for YT-type aluminum alloy with high cutting speed, good rigidity and high wear resistance. The guide block should use YT-type raw materials with high wear resistance. For the processing of ordinary alloy steel, all cutting tooth materials should be selected from this comprehensive type of raw materials. At this stage, YT798 is selected.
3.The angle of CNC blade adopts standard
The angle of CNC blades for deep hole machining depends on the raw materials. A reasonable CNC blade angle is very helpful to ensure the stability of the entire drilling pin process, chip breaking and improve the durability of the tool. The rake angle and rake angle of CNC blades are the most critical angles. Usually, the rake angle of each drilling edge is γ0 = 00, the difficult to process raw materials are γ0 = 1 ~ 30, the materials with good process performance are γ0 = 3 ~ 60, brittleness. Negative numbers can be used for cold-hardened materials; the back angle of the outer edge is usually α0 = 8 ~ 120, and the inner edge should be larger, and α0 = 12 ~ 150.
The above is about the design principle of deep hole drills, I hope to help you!