how to choose the right sandpaper product : 4 steps

choose the right sandpaper product

Sandpaper is one of the most commonly used abrasive tools, and its quality and selection have a great impact on the quality and efficiency of grinding. Therefore, choosing the appropriate sandpaper is very important. Choosing the right sandpaper not only improves work efficiency, but also affects the grinding effect and service life of the sandpaper due to differences in coarseness, material, and adhesive. Choosing the wrong sandpaper may result in low grinding efficiency and even longer time required to achieve the desired effect. Therefore, choosing the appropriate sandpaper can save time and cost, and improve work efficiency. Only by choosing the appropriate sandpaper can the efficiency and quality of the grinding process be ensured, and the smooth progress of work be guaranteed. Selecting the appropriate sandpaper product only requires considering four steps:

1.Sandpaper Shapes and Sizes

2.The differences between open-coat, semi-open-coat, and closed-coat sandpaper

3.Application of Sandpaper

4.What sandpaper products do we offer?

Sandpaper Shapes and Sizes

Sandpaper is a commonly used abrasive material for sanding and smoothing various surfaces. The shape and size of sandpaper vary and can be selected based on specific usage requirements. In this article, we will explore the shape and size of sandpaper.

Shape of Sandpaper

Different shapes of sandpaper are suitable for different applications, depending on the shape of the material surface that needs to be sanded or polished. Typically, the choice of sandpaper shape affects the efficiency and quality of sanding and polishing. Choosing the correct shape of sandpaper can make the job easier and more effective. We will introduce the different shapes of sandpaper and their usage scenarios in the table below.

Shape of Sandpaper	Applications
Square	Square (rectangular) sandpaper is one of the most common shapes of sandpaper. Its simple shape makes it easy to use, and it is suitable for polishing and sanding flat and straight surfaces. The edges can be trimmed with a blade to the desired shape. This shape of sandpaper can be handheld or mounted on a sandpaper base and is commonly used in sanding machines, handheld sanders, and manual sanding tools. Square sandpaper usually comes in different sizes and grit numbers to meet different needs.
Circular	Circular sandpaper is another common shape of sandpaper, typically used for polishing or sanding curved and circular surfaces, such as curved or cylindrical shapes of wood, metal, or plastic products. This shape of sandpaper is usually used in hand-held sanding machines, such as hand-held electric sanders, as well as fixed on a disc sander. Circular sandpaper also comes in different sizes and grit numbers for different applications.
Triangle	Triangle sandpaper is a type of sandpaper shape that is suitable for corners and hard-to-reach areas. This shape of sandpaper is typically used with a triangular sanding machine, but can also be used by hand. Triangle sandpaper can easily polish and sand corners, edges, and other hard-to-reach areas, such as corners of furniture or small decorations. This shape of sandpaper usually comes in different sizes and grit numbers to choose from.
Belt	Belt sandpaper is a commonly used abrasive tool, usually used to polish the surface of objects such as wood, metal, and plastic, to make them smoother or rougher. It is usually used for grinding and polishing work on handheld or electric belt sanders. Some belt sandpapers are designed as narrow strips, which allows users to perform precise grinding in small spaces. Other belt sandpapers are designed as wide strips, which can quickly and effectively smooth the surface of large objects.

The shape of sandpaper not only affects its usage, but also affects the distribution of sandpaper grit. For example, on a circular sandpaper, larger grits are typically located at the outer edge of the sandpaper, while smaller grits are located in the center. Therefore, when using sandpaper with different shapes, the position and angle of the sandpaper should be adjusted appropriately to achieve the best polishing effect.

Sandpaper Size

Sandpaper is a tool used to grind and polish material surfaces. Its size is one of the important factors that affect grinding effect and efficiency. When using sandpaper, choosing the appropriate size can reduce waste and improve work efficiency. Here is a detailed introduction to sandpaper size.

1.Length

The length of sandpaper is usually measured in meters, with common sizes being 1 meter, 5 meters, 10 meters, etc. Different grinding occasions require different lengths of sandpaper. For example, large area grinding requires longer sandpaper, while local grinding can use shorter sandpaper.

2.Width

The width of sandpaper is usually measured in millimeters, with common sizes being 25mm, 50mm, 100mm, etc. Similarly, different grinding occasions require different widths of sandpaper. For example, large area grinding requires wider sandpaper, while local grinding can use narrower sandpaper.

3.Grit Size

The grit size of sandpaper is usually expressed in sand grain numbers, such as P60, P100, P240, etc., with P standing for “sandpaper.” The smaller the grit size, the greater the grinding force, and the rougher the grinding effect. Conversely, the larger the grit size, the more delicate the grinding effect. The Coated Abrasive Manufacturers Institute (CAMI) has established sandpaper grit levels, which are divided into macroscopic and microscopic grit levels. Coarse grit sandpaper is used for harder materials such as hardwood and metal, while fine grit sandpaper is used for softer wood and sometimes even gypsum board.

	Coarse					Fine
	Extra coarse	Coarse	Medium	Fine	Finer	Finer	Extra fine	Ultra fine	Super fine
Applications	Removing impurities and initial sanding of hardwood floors	Quick removal of impurities	Removing paint	Used to remove water stains and plaster on wood	Sanding of wood	Sanding between different paint layers	Initial polishing of wood	Final sanding of wood	Final sanding and polishing
ISO/FEPA unit	P12-P36	P40-P50	P60-P80	P100-P120	P150-P220	P240-P360	P400-P600	P800-P1200	P1500-2500
CAMI unit	24-36	40-50	60-80	100-120	150-220	240	320-360	400-600	800-1000
Average particle diameter (micrometers)	1815-538	425-336	265-190	162-115	100-68	58.5-40.5	36-25.8	23-15.3	12.6-8.4

4.Particle Density

The particle density of sandpaper is usually measured in density units, including low density, medium density, high density, etc. The larger the particle density, the stronger the abrasive force, but the grinding speed may also become slower.

5.Backing Thickness

The backing thickness of sandpaper is usually measured in millimeters, with common values including 0.5mm, 0.8mm, 1.0mm, etc. The thicker the backing, the higher the durability of the sandpaper, but it may also affect the grinding effect.

In practical applications, different sizes of sandpaper can be used for different processing scenarios. For example, larger sandpaper is usually used for surface smoothing, while smaller sandpaper can be used for fine processing. In addition, the difference in the coarseness of the sand grains also has a significant impact on the processing effect. For instance, coarse sand grains can be used for quickly removing surface roughness, while fine sand grains can be used for surface finishing and polishing.

Overall, the selection of sandpaper size and coarseness should be based on specific processing scenarios and needs to ensure the best processing results.

The differences between open-coat, semi-open-coat, and closed-coat sandpaper

Open-coat sandpaper

Open-coat sandpaper is a type of coated abrasive that has an open pore structure. Its surface is coated with granular abrasive material with gaps between the particles called “pores.” These pores can store abrasive powder, lubricants, or cleaning fluids, enabling a continuous supply during grinding. Open-coat sandpaper is widely used for processes such as sanding, polishing, and cleaning. For example, in woodworking and metalworking, it can be used for sanding, polishing, and removing stains to achieve a better surface quality. In the semiconductor and optical industries, it can be used to manufacture precision components such as wafers and optical lenses. Open-coat sandpaper has several advantages compared to semi-open and closed-coat sandpaper, including:

• Continuous supply of abrasive powder, lubricants, or cleaning fluids, reducing work interruptions and maintenance time.
• The pore structure facilitates the release and dispersion of abrasive powder, reducing wear and heat buildup and extending the abrasive lifespan.
• The bond strength between the coating and the substrate is high, providing good wear and heat resistance.
• It can improve the smoothness and flatness of the grinding surface, making it more precise and even.

Semi-open-coat sandpaper

Semi-open coated abrasive paper is a type of abrasive with a partially open pore structure. Its surface is coated with a layer of granular abrasive material with gaps between the particles, called “pores.” These pores can store grinding powder, lubricants, or cleaning fluids, but not as effectively as open-coated abrasives. Semi-open coated abrasive paper has a wide range of applications in various industries, such as metalworking, automotive, and optics manufacturing. In metalworking, semi-open coated abrasives can be used for grinding, polishing, and cleaning. In the automotive industry, it can be used for surface treatment of parts such as wheels and car shells. In optics manufacturing, it can be used for the production of precision components such as optical lenses. Semi-open coated abrasive paper has several advantages:：

• It can store some grinding fluid, maintaining a certain degree of humidity during the grinding process, further reducing heat and wear.
• It can control the amount and fluidity of the grinding fluid used.
• It can prevent excessive accumulation of heat from the grinding fluid during the grinding process, improving efficiency and quality.
• The distribution of abrasive particles is more uniform than open-coated abrasive, resulting in a smoother and flatter grinding surface.

Closed-coat sandpaper

Closed-coat sandpaper has an extremely low abrasive porosity, with no gaps that allow grinding fluid to enter the abrasive material. This type of abrasive is typically made of materials such as metal or resin, and a thin film is formed on the surface of the abrasive to reduce direct contact between the abrasive and the work piece. Closed-coat sandpaper has a wide range of applications, including grinding and polishing materials such as metal, plastic, and ceramics. For high precision and surface quality requirements, closed-coat sandpaper can provide higher grinding efficiency and better surface quality. Additionally, in situations where it is necessary to avoid interaction between the abrasive and grinding fluid, closed-coat sandpaper can also be used. The advantages of closed-coat sandpaper include:

• The extremely low abrasive porosity prevents grinding fluid from entering the abrasive material, avoiding the problem of contaminating the work piece with grinding fluid.
• The abrasive has better contact with the grinding surface during the grinding process, thereby improving grinding efficiency and quality.
• The direct contact between the abrasive and work piece is reduced, resulting in reduced wear and heat generation, and an extended abrasive lifespan.
• The use of closed-coat sandpaper can improve grinding accuracy and surface quality, thereby achieving higher processing requirements.

Application of Sandpaper

Sandpaper is a product made of different sizes of abrasive particles attached to materials such as paper or cloth. By friction with the surface of the workpiece, it gradually flattens, polishes, and grinds the surface of the workpiece. Sandpaper has a wide range of applications, and below are some common ones that we will introduce.

Various Fields	Applications
In households	Sandpaper is used to repair damaged wooden furniture, remove surface stains, and for renovation and vehicle maintenance.
In the industrial sector	It is an important tool for polishing and grinding metal and plastic parts.
In construction projects	It is used to grind limestone, gypsum board, and other building materials.
In the woodworking industry	Sandpaper is used to smooth and shape the surface of wood, as well as to remove scratches and blemishes, and manufacture furniture or woodworking crafts.
In the automotive industry	It is used to remove blemishes, scratches, rust, and coatings on the surface of car paint, as well as to smooth metal surfaces.
In metal processing	It is used to grind and smooth the surface of teeth for filling and other treatments.
In dentistry	Sandpaper is used to grind and smooth the surface of teeth for filling and other treatments.
In the beauty industry	It is used to remove dead skin and smooth the surface of the skin for a better appearance.

What sandpaper products do we offer?

We offer high-quality sandpaper products from STARCKE, a leading manufacturer from Germany. STARCKE’s sandpaper products include dry and wet sandpaper, which can be used for grinding and polishing materials such as metal, wood, paint, and plastic. Dry sandpaper is suitable for coarse and medium grinding, while wet sandpaper is suitable for fine and ultra-fine grinding. In addition, the company also produces a range of waterproof sandpapers for wet grinding and polishing. Furthermore, depending on the specific application, sandpapers are available in different types and materials, as illustrated in the chart below.

Product – Sandpaper	Features	Segmented Markets	Suitable for
			hand sanding	hand held machine sanding	machine sanding
514D | 514C2	⇨The dust-repellent additive incorporated as top coat prevents premature-clogging of the grain surface. Unlike conventional stearate coating this-repellent effect is maintained throughout the product life. ⇨Full resinoid bonding ensures excellent performance and durability. ⇨It is best suited for grinding new generation water based lacquers. ⇨High durability, low clogging of the grain surface because of a 21-hole disc-system in our form 598. ⇨Best results will be achieved with the appropriate back-up pad also available-from Starcke.	1. Automobile repair   2.Furniture industry   3.Wind generator industry	❌	✔️	✔️
542C7 |  542B7	⇨Full resinoid bonding ensures excellent performance and durability. Also-suitable for brief damp sanding applications. ⇨The dust-repellent additive incorporated as top coat prevents premature-clogging of the grain surface. Unlike conventional stearate coating this-repellent effect is maintained throughout the product life. ⇨Brown aluminum oxide grain for maximum performance and durability.Designed to eliminate file marks on vehicle structures. ⇨A product with universal application possibilities, thus resulting in aneconominal stock keeping.	1.Automobile repair  2.Furniture industry  3.Wind generator industry	✔️	✔️	❌
641PF	⇨Full resin bonding and close coat leads to superior grinding characteristics. ⇨High quality aluminum oxide grain.	1.General off-hand grinding -Metal working   2.Off-hand grinding – Bodywork  3.General off-hand sanding – Wood working	✔️	❌	❌
713B	⇨Premium white aluminum oxide grain ⇨Easy handling due to a flexible bonding system ⇨The open coat prevents premature clogging of the paper ⇨Excellent price/performance ratio for hand sanding and hand-held machine sanding	1.Varnish 2.Paint 3.Wood	❌	❌	✔️

Product – Waterproof Sandpaper	Features	Segmented Markets	Suitable for
			hand sanding	hand held machine sanding	machine sanding
691A	⇨Short dipping in water is fully sufficient – no long soaking necessary. ⇨By using water, premature loading can be avoided which guarantees an-optimum life. ⇨No dust development. ⇨Flawless surfaces.	1.Automotive crash repair  2.Steel mills/Metallurgy  3.Optical industry-Lenses	✔️	✔️	❌
991A	⇨Excellent flexibility of soaked material. Extended soaking is no longer-necessary. ⇨By using the product under wet conditions premature loading can be-prevented, thus leading to a long life. ⇨No dust development. ⇨Perfect surfaces.	1. Automotive industry 2.Polishing paint 3.Polishing PVC	✔️	✔️	❌
991 C	⇨Excellent flexibility of soaked material. Extended soaking is no longer necessary. ⇨By using the product under wet conditions premature loading can be prevented, thus leading to a long life. ⇨No dust development. ⇨Perfect surfaces.	1.Automotive industry   2.Electronic industry  3. Jewelry industry	✔️	✔️	❌

Product – Polishing strips	Features	Segmented Markets	Suitable for
			hand sanding	hand held machine sanding	machine sanding
POLISHING STRIPS	⇨Consistent cutting performance and uniform surface roughness due to excellent coating of the abrasive grain. ⇨Ideal shapes for grinding small and fragile parts. ⇨Convenient and functional-packaging for protection and against contamination.	1.Clock and Watch Making Industry  2.Electronic Industry  3.Toolmaking Industry	✔️	❌	❌

Product – loop strips	Features	Segmented Markets	Suitable for
			hand sanding	hand held machine sanding	machine sanding
500 NET Korund	⇨ Suitable for clear coats, paints, fillers, wood, plastics ⇨ High quality with corundum abrasive for strong removal performance ⇨ Open mesh structure enables dense dust removal, long lifespan, and no clogging ⇨ Minimal dust emission, clean working environment promoted by special fabric	1.Automotive Repair 2.Paint Jobs 3.Woodworking	✔️	✔️	❌

Product – hook and loop strips	Features	Segmented Markets	Suitable for
			hand sanding	hand held machine sanding	machine sanding
732 EK Edelkorund	⇨Suitable for varnish, paint, putty, wood, metal ⇨Uses high-quality corundum abrasives for powerful sanding ⇨Even paper backing ensures a smooth sanding surface	1.Woodworking	✔️	❌	✔️
711 FS/NK	⇨Designed to conform to wavy surfaces to the greatest extent ⇨The low surface roughness for sanding can preserve the structure ⇨Can provide optimal sanding performance even in the most demanding designs	1.Paint Spraying 2.Clear Coat Sanding 3.Hand Sanding.	✔️	✔️	❌

References

• https://home.howstuffworks.com/polish-metal-sandpaper.htm
• https://pixabay.com/zh/users/detmold-2203847/
• https://www.starcke.de/fileadmin/user_upload/pdf/Katalog_2023_01.pdf