Particle size of "01" sandpaper


Sandpaper is not made of sand, but is composed of fine particles from natural or synthetic sources. The particles are sieved through a sieve and classified according to size, and then bonded to paper, sponge, or cloth backing with adhesive to make a self usable abrasive.


The requirements for each project are different, so it is important to distinguish the particle size of sandpaper.


In the United States, the particle size of sandpaper is determined based on the grade scale established by the Coating Abrasive Manufacturers Association (CAMI), expressed in units of "mesh". When we purchase sandpaper, we can see numbers such as 80 mesh, 100 mesh, or 200 mesh.


This means:


The higher the quantity, the smaller the particles, and the finer the particle size of the sandpaper.


On the contrary, lower numbers indicate larger grains and overall rougher sandpaper.


CAMI measures the particle size of sandpaper in "micrometers". To understand the concept of micrometers, we can examine a 100 mesh sandpaper. The size of small particles on sandpaper is about 141 microns, which is very small.


However, the sandpaper you purchase may comply with CAMI standards or FEPA standards. The particle size that meets the FEPA standard is represented by the initial letter "P" of "Particle".


Select the correct roughness for '02'


In order to facilitate people's selection, manufacturers will not only specify the grade, but also mark a "roughness grade" on the packaging. It is actually a particle size range suitable for similar polishing work.


In fact, most woodworking projects only require the selection of sandpaper with a certain roughness level, without the need to be precise to a specific sandpaper particle size. Therefore, it is important to know which project is suitable for each level.


The particle size range of ultra coarse sandpaper is between 24 and 36 mesh, used to remove paint and varnish that are difficult to peel off.


The strength of coarse sandpaper is to roughen the wood and remove the finish, such as a light colored polyurethane coating. Coarse particles usually range from 40 to 50 particle sizes.


Medium sandpaper, with a particle size range of 60-100 mesh, suitable for the final polishing before coating. Usually, we also use medium grain sandpaper to preliminarily polish rough wood to remove planning marks on the wood.


The particle size of fine sandpaper is 120-220 mesh. For most home workshops, this type of sandpaper is sufficient for final polishing before the work is completed.


Ultrafine sandpaper is often used between paints or varnishes. 240 mesh, 320 mesh, and 400 mesh abrasives are referred to as very fine abrasives, while special grade or ultrafine abrasives with particle sizes up to 600 mesh are most suitable for polishing operations.


Note: In many projects, you need to start with a rough sandpaper mesh and then switch to a finer mesh to achieve a smooth surface effect.



Select sand material for '03'


The factors that affect the success of polishing include not only the particle size of sandpaper, but also the type of abrasive.


Some types of sand particles are more suitable for smooth and sand type materials (e.g. wood and metal).


Most manufacturers list the most suitable material types for polishing on their product labels, but we can clarify the material types of sandpaper before shopping, which will be more helpful for woodcraft production.


Diamond sand: Natural particles. Diamond sand paper is often used to remove corrosion, polish steel, and other metals. The edges of its particles may be too sharp for frosted wood.


Garnet: Garnet is another natural particle that is slightly softer than diamond sand. Its circular edges can produce a smoother finish, but this also means that polishing is slower and the paper wears faster, making it an excellent choice for final polishing.


Aluminum oxide zirconia: This synthetic sand particle is durable and very suitable for grinding burrs on metals and preliminary rough grinding of wood. When using zirconia alumina to polish metal, the sand particles actually become sharper, so you don't need to change the sandpaper frequently.


Aluminum oxide: Aluminum oxide is a very durable synthetic coarse sand that is very suitable for polishing and polishing various types of metals (including bronze and alloy steel), and is also another common type of sandpaper used in woodworking projects. This is the most commonly used paper type in electric sanding machines. Aluminum oxide is more durable than garnet paper, but the surface effect is poor.


Silicon carbide: Silicon carbide is a very hard abrasive mainly used for repairing metals or "wet polishing" with water as a lubricant. Although some high-end finishes use silicon carbide paper, woodworking usually does not use it and it can be used for polishing metal woodworking tools.


Ceramic: Ceramic is a very hard abrasive. It can be used to remove wood quickly, such as belt sander and Bench grinder. It is both durable and expensive, but it does not produce a very smooth surface, so special care should be taken when using ceramic sandpaper, especially when using plywood and veneers, which can quickly polish the surface layer and damage it.