Common problems and solutions of cutting oil for deep hole drilling
October 13, 2022
In the machinery manufacturing industry, cylindrical holes whose hole depth exceeds 10 times the diameter of the hole are generally called deep holes. According to the ratio of hole depth to diameter (L/D), deep holes can be divided into general deep holes, medium deep holes and special deep holes. L/D=10 ~ 20, which belongs to general deep hole. It is often processed with extended twist drills on a drilling machine or lathe. L/D=20 ~ 30, it belongs to medium deep hole. Often processed on a lathe. L/D=30 ～## 100, which belongs to special deep hole. It must be processed on a deep hole drilling machine or special equipment using a deep hole drill.
Deep hole drilling has uniform cutting force distribution, good chip separation and chip breaking performance, stable and reliable drilling, and good straightness of the deep hole drilled, which is a link that cannot be ignored in the development of machining. During deep hole drilling, it is difficult to dissipate heat and remove chips, and the rigidity of the drill pipe is poor due to its slenderness, which is prone to bending and vibration. Generally, the cooling and chip removal are solved by means of a pressure cooling system. If the lubricating cooling medium is not selected properly, the following problems are prone to occur: 1. Big smoke 2. Chip evacuation is not smooth 3. The drill bit wears out fast There are many kinds of deep hole drilling cutting oils on the market. Compared with traditional cutting oils, the formula is basically the same, but the viscosity is different. Faced with these problems, as long as we scientifically analyze the processing characteristics of each process, and clearly understand the action mechanism of the three extreme pressure anti-wear additives of chlorine, phosphorus and sulfur, we can make full use of strengths and avoid weaknesses in various metal processing processes and use them accurately. Although deep hole drilling is a cutting process, it is different from traditional cutting. In practice, it is found that when traditional cutting is processing, multiple tools work at the same time, and the torque of each process is different. In the early stage of deep hole drilling, as soon as the drill bit contacts the workpiece, the pressure will reach about 2000N, and the temperature will increase instantaneously. The pressure is about 4000N. If the extreme pressure value (PD) of the selected oil is lower than 4000N or the release speed of the extreme pressure agent in the oil is slow, then smoke and rapid wear of the drill bit are inevitable.
Generally, 1:100 emulsion or extreme pressure emulsion is selected; when higher machining accuracy and surface quality or tough materials are required, extreme pressure emulsion or high concentration extreme pressure emulsion is selected, and the kinematic viscosity of cutting oil is usually selected (40). ℃) 10 ~ 20cm2/s, the cutting oil flow rate is 15 ~ 18m/s; when the machining diameter is small, use cutting oil with low viscosity; for deep hole machining with high precision, extreme pressure vulcanized oil with a cutting oil ratio of 40% can be selected +40% Kerosene+20% Chlorinated Paraffin.
