Key takeaways: 1. The selection of turning tools for lathe operations is contingent upon the specific application and material being machined, with various tools optimized for different tasks such as cylindrical turning, grooving, threading, and inner hole processing, each requiring tools with particular angles, structures, and materials to maximize efficiency and precision. 2. The rigidity and performance of turning tools are significantly influenced by their structure, with options ranging from integral types that offer simplicity and sturdiness, to machine clamp types that provide versatility through replaceable blades, and specialized tools like compound or damping cutters designed for specific, often more challenging operations. 3. Proper mounting of turning tools on a CNC lathe is critical for optimal performance and precision, necessitating careful attention to the tool's height relative to the workpiece center, the extension length from the tool holder, the flatness and alignment of the sizing block, and the perpendicularity of the tool bar to the feed direction to maintain the intended cutting angles and minimize vibration.
Classification by purpose
There are many kinds of turning tools, which can be divided into:
Cylindrical turning tool:
According to the main deflection angle, there are 95 degrees (for semi finishing and finishing of outer circle and end face), 45 degrees (for outer circle and end face, mainly for rough turning), 75 degrees (mainly for rough turning of outer circle), 93 degrees (mainly for profiling finishing) and 90 degrees (for rough and finish turning of outer circle).
The outer grooving turning tool is mainly used for outer circle grooving and cutting, and the inner grooving turning tool is mainly used for inner groove processing
Thread turning tool:
Thread turning tools are categorized into two types: external thread turning tools and internal thread turning tools. External thread turning tools are utilized for processing external threads, while internal thread turning tools are utilized for processing internal threads.
External thread turning tool
Internal thread turning tool
Inner hole turning tool:
It is mainly used for inner hole processing
According to the structure, it is divided into:
Integral type: The main body of the integral type tool is made from one piece and is not divided. This makes it easy to grind into sharp cutting edges, and the tool has good rigidity.
It is suitable for small turning tools and non-ferrous metal turning tools.
Related reading: Ferrous vs Non-ferrous Metals
Welding type: it is connected by welding method and divided into tool head and tool rod.
It has compact structure and convenient manufacture.
It is suitable for all kinds of turning tools, especially small tools.
Machine clamp type: the blade is fixed on the tool bar with a mechanical holder. The blade can be replaced after being blunt.
It is a commonly used tool for NC lathe. The tool bar is reused.
Special type: such as compound cutter, damping cutter, etc.
Classification by turning tool material
High speed steel tool:
It is made of high-speed steel and can be continuously polished, making it a general tool for rough and semi-finish machining.
Cemented carbide cutting tool:
The blade made of cemented carbide is suitable for cutting various materials including cast iron, non-ferrous metals, plastics, chemical fiber, graphite, glass, stone and ordinary steel. It is also capable of cutting challenging materials such as refractory steel, stainless steel, high strength steel, and tool steel.
The blade is embedded with diamond, which has the benefits of high hardness and resistance to wear, low friction coefficient, high elastic modulus, high thermal conductivity, low thermal expansion coefficient, and low affinity with non-metallic materials. It is suitable for precision processing of brittle and hard non-metallic materials such as graphite, high wear-resistant materials, composites, high silicon aluminum alloy, and other ductile non-ferrous metal materials.
Such as cubic boron nitride and ceramic cutting tools are being developed for rough machining and intermittent cutting of high-hardness alloy cast iron.
Mounting requirements of four station tool rest
1. The turning tool tip shall be at the same height as the rotation center of the workpiece.
Common methods of tool tip to center height: In the first step, when installing the turning tool, make sure that the tool tip is equal to the top of the tailstock. The second step is to perform a trial cut on the end face.
2. The length of the turning tool extending out of the tool holder shall be appropriate.
The turning tool is mounted on the tool holder. Generally, the length extending from the tool holder is 1-1.5 times the thickness of the tool bar, and it should not be too long. If the extension is excessive, the rigidity of the tool bar will deteriorate, making it prone to vibrating during cutting.
3. The sizing block of the NC lathe’s turning tool should be flat, and the smaller the number, the better. The sizing block should also be aligned with the tool holder to prevent vibration.
4. The NC lathe’s turning tool should be secured to the tool holder with a minimum of two screws, and they should be tightened one by one in sequence. The tightening force should be appropriate.
5. The centerline of the NC lathe’s turning tool bar should be perpendicular to the feed direction, otherwise the values of the main and auxiliary deflection angles will change. If the NC machine tool is different, the loading and unloading method will also be different.
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