For different types of cutting, the cutting characteristics of the metal are different, and the more difficult cutting processing requires higher cutting fluid. The difficulty of the cutting process is arranged in the order from difficult to easy as follows: internal broaching - external broaching - tapping - threading - hobbing - deep hole drilling - boring - cutting thread with forming tool - high speed low For cutting threads - milling - drilling - planing - turning (single-edged tools) - sawing grinding.
The above sequence is not absolute, because the geometry of the tool and the change in the material of the workpiece will also change the ease of processing. A brief description of how to select cutting fluids for some common machining methods.
1. turning, boring
Rough car: When roughing, the machining allowance is large, so the cutting depth and feed amount are large, the cutting resistance is large, a lot of cutting heat is generated, and the tool wear is also serious. It should be mainly used for cooling and has certain The water-based cutting fluid for cleaning, lubricating and anti-rusting takes the cutting heat away in time, reduces the cutting temperature, and thus improves the durability of the tool. Generally, the extreme pressure emulsion is better. In addition to good cooling performance, extreme pressure emulsion also has good extreme pressure lubricity, which can significantly extend tool life and improve cutting efficiency. Water-based cutting fluid should pay attention to the maintenance of machine tool guide surface, and workbench should be used before work. Dry the cutting fluid and apply oil.
Finishing car: When finishing the car, the cutting allowance is small, the cutting depth is only 0.05~0.8mm, the feeding amount is small, and the precision and roughness of the workpiece are required to be guaranteed. When the car is finished, the cutting force is small and the temperature is not high. Therefore, it is preferable to use a high concentration (10% or more) emulsion and a cutting fluid containing an oily additive.
Boring: The boring mechanism is the same as turning. However, it is bored and the cutting speed is not fast. However, the heat dissipation conditions are poor. The emulsion can be used as the cutting fluid. The flow rate and pressure of the cutting fluid should be increased appropriately.
Milling is interrupted cutting, and the cutting depth of each tooth changes momentarily, which is easy to generate vibration and a certain impact force, so the milling condition is worse than the turning condition. When high-speed tools are used for high-speed flat milling or high-speed end milling, cutting fluids with good cooling properties and certain lubricating properties, such as extreme pressure emulsions, are required. In low-speed milling, it is required to use lubricated cutting oils such as precision cutting oils and inactive extreme pressure oils. For stainless steel and heat-resistant alloy steel, cutting oils containing sulfur and chlorine extreme pressure additives can be used.
When the thread is cut, the tool is in wedge contact with the cutting material. The three sides of the blade are surrounded by the cutting material. The cutting torque is difficult to remove the chip. The heat cannot be taken away by the chip liquid in time. The tool is easy to wear, the chip debris is congested and the vibration is easy to occur.
Especially in the threading and tapping, the cutting conditions are more severe, sometimes there will be chipping and broken taps, and the cutting fluid is required to have both lower friction coefficient and higher extreme pressure to reduce the frictional resistance of the tool and prolong the service life of the tool. Generally, a composite cutting fluid containing both an oily agent and an extreme pressure agent should be used.
In addition, the penetration performance of the cutting fluid during thread tapping is very important. Whether the cutting fluid can penetrate into the cutting edge in time has a great influence on the durability of the tap. The permeability of the cutting fluid is related to the viscosity, and the oil with low viscosity is better. If necessary, a small amount of diesel or kerosene may be added to enhance the seepage effect. In some occasions, such as the blind hole tapping thread, it is difficult for the cutting fluid to enter the hole. In this case, the effect of the cutting fluid with high viscosity and strong adhesion is better.
Reaming is the precision machining of the hole. It requires high precision. Reaming is a low-speed small-feed cutting. The main tool is the extrusion cutting of the tool and the hole wall. The chip fragments are easy to remain in the sipe or adhere to the edge of the blade, affecting the edge. Extrusion, damage processing accuracy and surface roughness increase cutting torque, and also produce built-up edge, increase tool wear reaming is basically a boundary lubrication state, generally adopting high concentration extreme pressure with good lubrication performance and certain goodness Good results can be obtained with emulsion or extreme pressure cutting oil.
For deep hole reaming, deep hole drilling cutting oil with good lubrication performance can meet the process requirements.