Tungsten is ideal for broad applications but it is not an easy-to-machine alloy, in this article, we want to talk about the tungsten machining challenges, speeds & feeds, processes, and cutting fluid.
Tungsten can be CNC machined, but not easy to machine, it is known to be a challenging material to work with due to the following factors. Machining tungsten typically requires specialized tools, cutting techniques, and equipment capable of handling its properties.
– High hardness: Tungsten is one of the hardest materials, ranking close to diamond on the Mohs scale. Its high hardness makes it difficult to cut and requires the use of specialized cutting tools that can withstand the abrasive nature of tungsten.
– High melting point: Tungsten has an exceptionally high melting point of around 3,400 degrees Celsius (6,152 degrees Fahrenheit). Machining tungsten generates a significant amount of heat, and the high melting point of the material can result in rapid tool wear and deformation if proper cutting techniques and cooling strategies are not employed.
– Brittle nature: Tungsten is a brittle material, which means it has a tendency to crack and fracture under stress. Machining processes can introduce forces that may lead to chipping or breakage if not controlled properly. Care must be taken to mitigate any sudden or excessive loads imposed on the material.
– Density: Tungsten has a high density, which can make it challenging to machine due to the increased cutting forces required. Higher cutting forces can lead to tool deflection, vibration, and reduced machining accuracy if not managed effectively.
– Chip control: Tungsten produces short, hard chips during machining, which can present difficulties in chip evacuation. These chips can be challenging to remove from the machining zone, potentially causing tool clogging or jamming.
The speeds and feeds for machining tungsten will be determined by the specific grade of tungsten, tooling conditions, machine rigidity, and desired surface finish.
1. Cutting speed: Keep the cutting speed relatively low when machining tungsten. A recommended range is typically between 50 to 150 surface feet per minute (SFPM), or about 15 to 45 meters per minute (MPM).
2. Feed rate: Opt for a relatively low feed rate to prevent excessive tool wear and to maintain cutting accuracy. A recommended range is typically between 0.002 to 0.010 inches per revolution (IPR), or about 0.05 to 0.25 millimeters per revolution (MMR).
3. Depth of cut: Take shallow depths of cut to reduce tool load and potential vibration. A range of 0.010 to 0.050 inches (0.25 to 1.27 millimeters) is often suitable.
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1. Turning: This process involves rotating the workpiece and cutting tools against each other to remove material from the surface of the tungsten. It can be done on a lathe machine.
2. Milling: In milling, a rotating cutting tool removes material from the workpiece. It is commonly used to create complex shapes and contours in tungsten. Carbide or diamond-coated tools are often employed for milling tungsten due to its hardness.
3. Drilling: Tungsten can be drilled to create holes using twist drills or specialized carbide drills. The high hardness of tungsten requires the use of appropriate cutting speed and coolant to dissipate heat generated during the drilling process.
4. Grinding: Grinding involves the use of an abrasive wheel to remove material from the surface of tungsten. It is often used for achieving tight tolerances, precise surface finishes, and shaping tungsten components.
5. Electro-discharge machining (EDM): EDM is a non-contact machining process that utilizes electrical sparks to remove material from tungsten. It is commonly used for intricate and complex shapes that are difficult to achieve with conventional machining methods.
1. Water-based cutting fluid: Water-soluble cutting fluids, such as emulsions or synthetic coolants, can be used for machining tungsten. These fluids provide cooling and lubrication, helping to extend tool life and improve surface finish.
2. Straight cutting oil: Straight cutting oils, such as mineral oils or synthetic oils, are commonly used for machining tungsten. They provide excellent lubrication and heat dissipation properties. However, they may require special consideration for chip evacuation.
3. Cutting oil with EP additives: If the machining operation involves heavy cutting or higher loads, a cutting oil with extreme pressure (EP) additives can be used. These additives provide improved lubrication and protection against tool wear.
4. Dry machining: In some cases, dry machining without the use of cutting fluids may be feasible for tungsten. However, it is important to consider the increased risk of heat buildup and tool wear when opting for dry machining.