Types of turning tool and related knowledge (HY-industry technical centre)

Types and uses of turning tools

1. Types and uses of turning tools

• Turning tools are the most widely used single-edged tools. It is also the basis for learning and analyzing various tools. Turning tools are used to process outer circles, inner holes, end faces, threads, grooves, etc. on various lathes. According to the structure, it can be divided into integral turning tools, welding turning tools, machine clamp turning tools, indexable turning tools and forming turning tools. Among them, the application of indexable turning tools is becoming more and more extensive, and the proportion of turning tools is gradually increasing.

2. Carbide welding turning tool

• So-called welding turning tool is a turning tool used after opening a groove on the carbon steel tool holder according to the geometric angle of the tool, welding the carbide blade in the groove with solder, and grinding the geometric parameters according to the selected tool.

3. Machine clamp turning tool

• Machine clamp turning tool is a turning tool that uses ordinary blades to clamp the blade on the tool bar through mechanical clamping. This kind of knife has the following characteristics:
  The blade does not undergo high-temperature welding, which avoids defects such as blade hardness drop and cracks caused by welding, and improves the durability of the tool.
  With the improvement of tool durability, the use time is longer, the tool change time is shortened, and the production efficiency is improved.

• Tool bar can be reused, which not only saves steel but also improves the utilization rate of the blade. The blade is recycled and remanufactured by the manufacturer, which improves the economic efficiency and reduces the cost of the tool.

• After the blade is regrinded, the size will gradually become smaller. In order to restore the working position of the blade, the blade adjustment mechanism is often set on the turning tools structure to increase the number of blade regrinding.

• The end of the pressing plate used for pressing the blade can act as a chip breaker.

4. Indexable turning tools

Indexable turning tool is a machine clamp turning tool that uses indexable inserts. After a cutting edge is blunt, it can be quickly indexed and replaced with a new adjacent cutting edge, and the work can continue until all the cutting edges on the blade are blunt, and the blade is scrapped and recycled. After replacing the new blade, the turning tools can continue to work.

1. Advantages of indexable tools Compared with welding tools, indexable tools have the following advantages:

• High tool life. Because the blade avoids the defects caused by welding and sharpening high temperature, the geometric parameters of the tool are completely guaranteed by the blade and the shank groove, and the cutting performance is stable, thereby increasing the tool life.

• High production efficiency. Since machine tool operators no longer sharpen their tools, auxiliary time such as stopping the machine to change tools can be greatly reduced.

• It is conducive to the promotion of new technologies and processes. Indexable knives are conducive to the promotion of the use of coatings, ceramics and other new tool materials.

• Conducive to reducing tool costs Due to the long service life of the tool holder, the consumption and inventory of the tool holder are greatly reduced, the management of the tool is simplified, and the cost of the tool is reduced.

2. Clamping characteristics and requirements of indexable turning tools inserts

• High positioning accuracy After the blade is indexed or replaced with a new blade, the change in the position of the tool tip should be within the allowable range of workpiece accuracy.

• Reliable clamping of the blade. Ensure that the contact surfaces of the blade, shim, and shank are in close contact and can withstand shock and vibration, but the clamping force should not be too large, and the stress distribution should be uniform to avoid crushing the blade.

• Smooth chip removal The front of the blade is best to be free of obstacles to ensure smooth chip removal and easy observation.

• Easy to use It is convenient and quick to change the blade and replace the new blade. For small-sized tools, the structure should be compact. When meeting the above requirements, the structure should be as simple as possible, and the manufacture and use should be convenient.

5. Forming turning tool

• Forming turning tool is a special tool for processing the forming surface of the revolving body. Its blade shape is designed according to the profile of the workpiece. It can be used on various lathes to process the forming surface of the inner and outer revolving bodies. The surface of the part can be formed at one time when the part is processed by the forming turning tools. The operation is simple and the productivity is high. After processing, it can reach the tolerance level IT8～IT10, the roughness is 10～5μm, and can ensure high interchangeability. However, the manufacturing of forming turning tool is more complicated, the cost is higher, and the working length of the blade is wider, so it is easy to cause vibration. Forming turning tools are mainly used to process large batches of small and medium-sized parts with forming surfaces.

• If a worker wants to do well, he must first sharpen his tools. In order to make good cutting on a lathe, it is very important to prepare and use the tools correctly. Different jobs require turning tools of different shapes. Cutting different materials requires different cutting angles. The position and speed of the turning tools and the workpiece should have a certain relative relationship. The turning tools itself should also have sufficient hardness, strength and Wear-resistant and heat-resistant. Therefore, how to choose the turning tools material and the grinding of the tool angle are all important considerations.

Types and uses of turning tool materials

The improvement and development of tool materials is one of the important issues in the development of today’s metal processing, because a good tool material can effectively and quickly complete the cutting work and maintain a good tool life. Generally, there are the following materials for turning tools:

1. High carbon steel:

• High-carbon steel turning tool is a carbon steel with a carbon content of 0.8% to 1.5%. It is used after quenching and hardening. It is easy to temper and soften due to friction during cutting and is replaced by other tools such as high-speed steel. Generally only suitable for the cutting of soft metal materials, commonly used ones include SK1, SK2,,,, SK7, etc.

2. High-speed steel:

• High-speed steel is a kind of steel-based alloy commonly known as white turning tools. It is made by adding alloy elements such as W, Cr, V and Co to carbon steel with a carbon content of 0.7~0.85%. For example, 18-4-4 high-speed steel material contains 18% tungsten, 4% chromium and 4% vanadium high-speed steel. The friction heat generated in the cutting of high-speed steel turning tools can be as high as 6000C, which is suitable for turning speeds below 1000rpm and thread turning. Generally, high-speed steel turning tools such as SKH2, SKH4A, SKH5, SKH6, SKH9, etc. are commonly used.

3. Non-cast iron alloy tools:

• This is an alloy of cobalt, chromium and tungsten. It is also called superhard cast alloy because it is difficult to cut and is manufactured by casting. The most representative is stellite. Its tool toughness and wear resistance are extremely good, at a temperature of 8200C Its hardness is still unaffected, and its heat resistance far exceeds that of high-speed steel, which is suitable for high-speed and deep cutting work.

4. Sintered carbonized tool:

• Carbide tool is a powder metallurgical product. The main component of the tungsten carbide tool is 50% to 90% tungsten, and titanium, molybdenum, tantalum, etc. are added with cobalt powder as a binder, and then heated and sintered. The hardness of the carbonized tool is higher than that of any other material. It is three times the hardest high carbon steel. It is suitable for cutting harder metals or stones. Because of its brittle material, it can only be made into a sheet shape and then welded to have more toughness. On the knife handle, when the blade is dull or cracked, you can replace it with another cutting edge or a new blade. This kind of turning tool is called a throwaway turning tool.

• Carbonized tools are divided into three categories: P, M, and K according to the different cutting properties of the international standard (ISO), and they are marked in three colors: blue, yellow, and red:

• Type P is suitable for cutting steel. There are six types of P01, P10, P20, P30, P40, P50. P01 is a high-speed precision turning tools with a small number and high wear resistance. P50 is a low-speed rough turning tools with a large number and high toughness. , The handle is painted blue to identify it.

• K category is suitable for cutting hard and brittle materials such as stone and cast iron. There are five categories: K01, K10, K20, K30, K40. K01 is a high-speed precision turning tool, and K40 is a low-speed rough turning tools. This type of tool holder is painted in red for identification.

• M type is between P type and M type. It is suitable for cutting materials with greater toughness, such as not sock, etc. This type of tool holder is painted yellow to identify it.

5 Ceramic turning tools:

• Ceramic turning tools sare made of alumina powder, added a small amount of elements, and then sintered at high temperature. Its hardness, heat resistance and cutting speed are higher than tungsten carbide, but because of its brittleness, it is not suitable for discontinuous or heavy turning. Only suitable for high-speed finishing.

6 Diamond knives

• For high-level surface processing, industrial diamonds with round shapes or edges on the surface can be used for polishing. A smoother surface can be obtained. It is mainly used for precision turning of copper alloys or light alloys. High speed must be used during turning, with a minimum of 60~100m/min, usually 200~300m/min.

7 Boron oxide

• Cubic boron oxide (CBN) is a material that has been promoted in recent years. Its hardness and wear resistance are second only to diamonds. This tool is suitable for processing hard and wear-resistant iron group alloys, nickel-based alloys, and cobalt-based alloys.

Tool shape and usage

1 There are the following types of generally used turning tool tips:

1. Rough turning tool: It is mainly used to cut a large number of excess parts to make the diameter of the workpiece close to the required size. The surface finish is not important when rough turning, so the tip of the turning tools can be ground into a sharp peak, but the peak usually has a small roundness to avoid breakage.

2. Fine turning tool: This blade can be polished with oil stone to make a very smooth surface finish. Generally speaking, the round nose of a fine turning tool is larger than that of a rough turning tools.

3. Round nose turning tool: It can be used for many different types of work. It is a common turning tool. When the top surface is flattened, it can be turned left and right and can also be used to turn brass. This turning tool can also form an arc surface on the shoulder corner, and can also be used as a fine turning tool.

4. Cut-off turning tool: Only the end is used to cut the workpiece. This turning tool can be used to cut materials and turn grooves.

5. Screw turning tool (tooth knife): used for turning screw or nut, 60 degree or 55 degree V-shaped tooth knife, 29 degree trapezoidal tooth knife, square tooth knife according to the thread form.

6. Boring turning tool: used for turning drilled or cast holes. The purpose is to achieve the light system size or the true straight hole surface.

7. Side turning tool or side turning tool: used to turn the end face of the work object, the right turning tool is usually used at the end of the finishing axis, and the left turning tool is used to finish turning the left side of the shoulder.

2. Different blade shapes are used due to the different processing methods of the workpiece, which can generally be divided into:

1. Right-hand turning tool: Turning the outer diameter of the workpiece from right to left.

2. Left-hand turning tool: Turning the outer diameter of the workpiece from left to right.

3. Round nose turning tool: The cutting edge is arc-shaped, which can be turned in the left and right directions, suitable for turning round corners or curved surfaces.

4. Right turning tool: turning the right end face.

5. Left turning tool: Turning the left end face.

6. Cutting knife: used for cutting or grooving.

7. Inner hole turning tool: used for turning inner hole.

8. External thread turning tool: used for turning external threads.

9. Internal thread turning tool: used for turning internal threads.

Name and function of each part of the turning tool

• Turning tool is a single-edge tool, and there are many types due to the different shapes of the turning work, but the names and functions of its parts are the same. A good turning tool must have a rigid handle and a sharp blade. The cutting edge angle of the turning tool directly affects the turning effect. Different turning tool materials, workpiece materials, and cutting edge angles are also different. Turning tool for lathes have four important angles, namely, front clearance angle, side clearance angle, back bevel angle and side bevel angle.

1 Front clearance angle

• Angle that is inclined from the nose down to the inside of the tool is the front clearance angle. Because of the front clearance angle, a space is formed under the working surface and the nose, so that the cutting action is concentrated on the nose. If the angle is too small, the tool will rub on the surface, and a rough surface will be produced. If the angle is too large, the tool is prone to tremor, making the nose fragmented and unable to be polished. When installing a turning tool with a tilted middle handle to grind the front clearance angle, the tilt angle of the handle needs to be considered. For high-speed steel turning tool, this angle is between 8 and 10 degrees, while for carbide turning tool, it is between 6 and 8 degrees.

2 side clearance angle

• Angle at which the side of the knife inclines from the cutting edge to the inside of the knife is the edge clearance angle. The edge clearance angle forms a space between the work surface and the knife side, so that the cutting action is concentrated on the cutting edge to improve cutting efficiency. The angle of high speed steel turning tool is about 10~12 degrees.

3 Back bevel

• Inclined angle from the nose of the knife to the handle from the top surface of the knife is the back bevel. This angle is mainly to guide chip removal and reduce chip removal resistance. For cutting general metals, high-speed steel turning tool are generally 8-16 degrees, while carbide turning tool are negative or zero degrees.

4 side bevel

• Cutting edge is inclined from the cutting edge to the other side from the top surface of the knife, and the angle formed by this inclined surface and the horizontal plane is the side bevel. This angle is the angle at which the chips can be separated from the work, so that chip removal is easy and effective turning can be obtained. For cutting general metals, the angle of the high-speed steel turning tool is about 10~14 degrees, while the carbide turning tool can be positive or negative.

5 Knife end angle

• Angle between the front end of the blade and the shank perpendicular to it. The function of this angle is to maintain a gap between the front end of the blade and the workpiece to avoid friction between the blade and the workpiece or scratch the processed surface.

6 Cut corners

• Angle between the front end of the blade and the shank perpendicular to the handle is used to change the thickness of the cutting layer. At the same time, the cutting edge angle can also change the force direction of the turning tool, reduce the feed resistance, and increase the tool life. Therefore, in general rough turning, a turning tool with a larger trimming angle should be used to reduce the feed resistance and increase the cutting speed.

7 Nose radius

• Arc radius of the knife edge at the highest point of the knife edge. The nose radius is large and the strength is large. It is used for large cutting depth, but it is prone to high frequency vibration.

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