Turning is a machining method that achieves the target shape by cutting materials, and it is classified as a cutting process. The turning process can realize the machining of complex shapes through the combination of various cutting tools and processing methods. The following will introduce its characteristics, processing steps, etc.

What is Turning?

Turning is a type of cutting process. Other cutting processes include milling and drilling. In turning, a cutting tool is fed into a rotating workpiece, and the desired shape is formed by cutting off the unnecessary parts.

Turning is similar to milling, which also belongs to cutting processes. The difference lies in “what is rotated”. In turning, the workpiece (the material to be processed) is rotated, while in milling, the workpiece is fixed and the cutting tool rotates to complete the processing.

Basic Machining Methods of Lathes

Turning includes eight basic machining methods: facing, outer diameter turning, chamfering, inner diameter turning, threading, drilling, parting, and knurling. The following explains each method:

Facing

During processing, the length of the workpiece is slightly longer than the length the final part should have. Facing is a machining operation used to process the end of the workpiece perpendicular to the axis of rotation. During turning, the lathe tool moves along the radius of the workpiece, removing a thin layer of material to produce the desired part length and a smooth surface.

Outer Diameter Turning

Outer diameter turning is a method in which a cutting tool is applied to the outer side of a rotating material for processing. Even in turning, this is the most commonly used method, which is used for finishing the surface or roughing out the approximate target shape in the initial stage of processing.

In outer diameter turning, chips may wrap around the tool. Especially in finishing that requires high precision, the tool angle must be adjusted to prevent chip wrapping and precision degradation.

Chamfering

On a lathe, special chamfering tools can be used, and turning can be performed by selecting different tool angles and sizes as needed.

Turning chamfering refers to forming a bevel (usually a 45-degree angle) on the edge of a workpiece or the inner and outer edges of a hole through turning. It is used to remove burrs and sharp corners, improving the safety, assemblability, and aesthetics of the workpiece.

Inner Diameter Turning

Inner diameter turning involves cutting the inner side of the material to expand a hole drilled in the material (e.g., through drilling). It can be used to adjust the size of the hole and finish the inner surface.

In inner diameter turning, the length of the tool must be increased according to the depth of the hole to be processed. However, it should be noted that an excessively long tool is prone to bending, leading to precision degradation. In addition, chips will remain in the hole, so they need to be removed frequently.

掘削

Drilling is a method in which a drill bit is pressed against a rotating material to drill a hole. When performing inner diameter turning, a hole must first be drilled to allow the special tool to enter, and at this time, the drilling process is required.

Since the precision of drilling with a drill bit is not very high, after drilling a hole of the required size, subsequent finishing is usually performed by inner diameter turning.

Threading

Threading is a processing method used to make screw threads. Internal and external threads can be machined by turning with a special threading tool. Milling and machining centers can mostly only machine internal threads, and one of the main advantages of turning is that it can machine external threads.

A special threading tool is applied to the material, and the tool is moved at a constant speed. To ensure that the thread pitch remains equidistant, the “automatic feed function” is mostly used to keep the speed constant.

Parting

Parting is a processing method in which a tool is pressed against the material to cut off the unnecessary part, such as circumferential cutting of a cylinder.

Knurling

Lathe knurling is a processing method that uses a knurling tool on a lathe to roll out specific textures on the surface of a workpiece. This processing is mainly used to increase the friction or aesthetics of the workpiece surface. The knurling patterns usually include straight and reticulated patterns, and different thicknesses can be selected as needed.

Advantages and Disadvantages of Turning

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• Turning can process circular products. In addition, since cutting is performed while the material is rotating, high dimensional accuracy can be achieved, which is also an important advantage.
• The rotation speed and rotation method can be changed arbitrarily. In addition, there are many types and ranges of tools according to different applications. By combining with processing methods, products with complex shapes can be manufactured.

Disadvantages

• Although turning can achieve complex shapes by combining various tools and processing methods, the more frequently the tools are replaced, the longer the time required to produce a product.
• In addition, to make full use of various processing methods, skilled operators are required, so not everyone can produce high-precision products. It is necessary to select the appropriate processing method according to the complexity of the product and the technical level of the operator.

Turning Steps

The steps of turning will vary slightly depending on the product being made. Here, only the typical general steps are explained:

Installing Tools and Materials

First, install the cutting tools and materials used for turning. They must be firmly installed to ensure that they do not loosen during processing. If the installation position is offset, the precision will decrease, so high-precision positioning is important.

Rough Machining

Next, rough machining is performed to turn out the approximate shape of the product to be made. This process does not require high precision, but care must be taken not to cut too much. In addition, attention should be paid to the rotation state of the material and the occurrence of chips.

仕上げ

After rough machining to turn out the approximate shape of the product, finishing is finally performed. Since high precision is required, close attention should be paid to the rotation speed and feed rate during finishing. If burrs appear, care should be taken to remove them with a file without damaging the machined surface.

Precautions for Turning Parts

When turning parts, it is necessary to achieve the required precision at the lowest possible cost.

In designing parts, the focus is on reducing the amount of material that needs to be cut and shortening the processing time. In addition, ensuring that the product can be processed without using special tools and with regularly sold tools helps shorten the delivery time and reduce costs.

When performing turning, it is important to determine the processing sequence and select tools on the premise of not making the steps too complicated.

概要

Turning is a type of cutting process, which involves applying a cutting tool to a rotating material for processing. Lathes can perform operations such as outer diameter turning, inner diameter turning, threading, drilling, and parting. General lathes can be divided into universal lathes, NC lathes, desktop lathes, front-facing lathes, and vertical lathes, etc., and they need to be used according to different purposes.