What is grinding? An easy-to-understand explanation of the types, characteristics, and differences from cutting

Grinding is a processing method for parts that require high-precision finishing and dimensional adjustment in microns. It is used mainly as a finishing process in metal processing because it can achieve high-quality processing that cannot be achieved by cutting alone. Understanding the overview of grinding will help you select the optimal processing method and manage quality.

In this article, we will explain the definition of grinding, the structure of a grinding wheel, and the differences between grinding, cutting, and polishing.We also introduce materials that are suitable for grinding, so please refer to it.

What is grinding?

Grinding is a process in which a rotating grinding wheel or other grinding tools are used toThis is a processing method in which the surface of the target material (workpiece) is gradually removed to make it smooth.It is used for final finishing and machining of high-hardness materials with the aim of improving surface finish and dimensional accuracy.

For example, reducing frictional resistance, improving durability, and improving noise reduction are important for automobile engine parts, bearings, molds, etc. Grinding allows the surface roughness (Ra) to be controlled to the level of a few microns, resulting in higher part performance.

Structure of the grindstone

Grinding wheels, which are essential for grinding, are made up of the following three elements. We will look at the role of each.

When the grinding process wears down the whetstone, the grains naturally fall off and new abrasive grains appear, maintaining the sharpness of the whetstone. Due to this self-sharpening process, the whetstone can basically maintain its performance without being polished.

However, in order to take into account grinding accuracy, surface roughness, and tool life, it is necessary to select an appropriate grinding wheel and reshape (dress) the grinding wheel surface.

Differences between grinding, cutting and polishing

"Grinding," "cutting," and "polishing" are terms with similar images, so let's take a look at the differences between each processing method.

1. Differences between grinding and cutting
2. Difference between grinding and polishing

Differences between grinding and cutting

Grinding and cutting are both processes that cut material to shape it.Grinding is generally used for final finishing, while cutting is used for rough processing.

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What is cutting? A thorough explanation of the types, characteristics, and typical parts that can be produced.

What is the difference between grinding and cutting? Key points for choosing the right one in precision machining

Difference between grinding and polishing

The purpose of both grinding and polishing is to finish the surface.Polishing is generally used as an auxiliary process to improve aesthetic appearance.

The main types of grinding

There are several types of grinding depending on the purpose, shape, and object to be processed.Here we will explain the characteristics and applications of each of the major grinding methods.

1. Surface grinding
2. Internal Grinding
3. Cylindrical grinding
4. Centerless Grinding
5. Gear grinding

Surface grinding

Surface grinding is a grinding method that smooths the flat surface of the workpiece.As the grinding wheel rotates, it comes into contact with the workpiece from a horizontal or vertical direction, gradually removing the surface.

It is used for processing parts where flatness control is important, such as metal plates, plates, and the contact surfaces of molds.

Internal Grinding

Internal grinding is a grinding method used to process the inner diameter of cylindrical parts.The workpiece is rotated and a grinding wheel rotating in the opposite direction is inserted inside the hole to grind it.

It is used for parts that require high precision inner diameters, such as the inner rings of bearings and the inside of hydraulic cylinders, and for adjusting roundness.

Cylindrical grinding

Cylindrical grinding is a grinding method in which the outer diameter of a cylindrical workpiece is processed with a grinding wheel.The workpiece and the grinding wheel are rotated in the same direction to grind the surface.

It is used to improve the roundness and cylindricity precision and surface smoothness of shafts, rollers, pins, etc.

Centerless Grinding

Centerless grinding is a method of grinding a cylindrical workpiece by grinding the workpiece with a grinding wheel, a support blade, or aThis is a grinding method in which the material is clamped with a regulating wheel and sent out while being ground.

It is suitable for mass production because it can be processed continuously. It is used to improve the roundness and concentricity of the outer diameter of shafts and pins, etc.

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Centerless grinding

Gear grinding

Gear grinding is a grinding method used to further improve the tooth surface accuracy of already machined gears.A hobbing machine or forming wheel is used to adjust the gear shape, surface roughness, pitch, etc.

It is used to suppress operating noise and wear.

Characteristics of grinding processing [Advantages]

Here we will introduce three typical advantages of grinding.

1. High precision and high quality finish
2. Capable of machining hard materials
3. Surface roughness is adjusted

High precision and high quality finish

Grinding produces little deformation and is less susceptible to the effects of heat and cutting stress, resulting in extremely high dimensional accuracy.Generally, parts with tolerances of 0.0001mm to 0.0005mm can be machined, making it essential for precision equipment and aerospace parts.

We can also process difficult-to-cut materials such as ceramics and cemented carbide, as well as ceramics.

Capable of machining hard materials

The grinding stones used in grinding have a self-sharpening property, which keeps the stone sharp.Therefore, it can be used even if the abrasive grains are softer than the work material.

It is often used for materials that are hard and difficult to cut, and for finishing processes after hardening.

Surface roughness is adjusted

The action of the grinding stone gradually removes the surface of the workpiece, resulting in a smooth finish.It is possible to achieve a finish with an Ra (arithmetic mean roughness) of 0.2 μm or less, which contributes to reducing friction, improving adhesion, and ensuring quietness.

Points to note about grinding [Disadvantages]

Here we will introduce three typical disadvantages and points to note regarding grinding.

1. Processing time is long and costly
2. Risk of burning and dimensional changes due to heat
3. Accident prevention education and measures are important

Processing time is long and costly

Grinding takes time because only a very small amount of material is removed per process.Since its main purpose is to adjust the surface roughness, it is generally used in combination with cutting when removing a large amount of material.

Additionally, managing tools, such as preventing wear and tear on grinding wheels and dressing them, also incurs costs.

Risk of burning and dimensional changes due to heat

During grinding, the grinding wheel rotates at high speed, and friction can cause the processed area to reach temperatures exceeding 1,000°C.This heat can cause the surface to burn or the dimensions to change slightly due to thermal expansion, which can lead to deterioration.

Therefore, the higher the machining precision, the more advanced the management of coolant and grinding wheels is required.

Accident prevention education and measures are important

In grinding, the grinding wheel rotates at high speed, so there is a risk of accidents due to the grinding wheel breaking or the workpiece flying off. For example, if the grinding wheel is used at a speed exceeding the maximum safe operating speed or if the workpiece is pressed against it too hard, the grinding wheel may break or fly off, leading to an accident.

For this reason, it is essential to implement thorough safety measures, such as pre-work inspections, safety training, and wearing protective equipment.

Grindstone material suitable for grinding

In grinding, it is important to use different types of grinding wheels depending on the material of the workpiece.Common grinding wheel materials are alumina (Al₂O₃) and silicon carbide (SiC), but diamond and CBN (cubic boron nitride), which is made from boron and nitrogen, may also be used.

Here we will introduce the main types of abrasive grains and the main workpiece materials for which each is suitable.

Summary of grinding process

Grinding is a process that requires dimensional accuracy and surface roughness in microns, and is essential for high-precision parts. Since the processing quality is greatly affected by the selection of the material, grindstone, and machine tool, it is important to determine the grinding conditions, grindstone material, and processing technology according to the application.

Sanwa Needle Bearings is capable of ultra-precision grinding to within ±0.0001mm, including processing using equipment developed in-house.With grinding as our core technology, we are able to carry out integrated in-house production, including other processes such as cutting, plasticity, grinding, and heat treatment.

Regardless of the material or lot size, if you have any problems with grinding, please feel free to contact us.