Square shaped shims and round shims are two common fasteners, mainly used for connecting the gap and stress distribution between bolts, nuts and connecting parts to reduce friction, limit deformation, transfer pressure and prevent air and liquid leakage.

• Shape: Square shims are in quadrilateral shape with equal side lengths and 90-degree angles; round shims are round with uniform circumferential edges.
• Application scenarios: Square shims are suitable for certain square or regular structural connections and bolt holes due to their shape characteristics, mainly used for track connections such as angles, I-beams and rails; round shims are suitable for a wide range of scenarios and are more commonly used.
• Material: Both can use various metal and non-metallic materials, such as steel, copper, aluminium, rubber, silicone, etc., selected based on different working conditions.
• Installation effect: Round gasket edges provide continuous circumference with more uniform stress distribution; square gaskets may have force concentration at corners.
• Torque control: Generally easier to control during installation of round shims due to uniform pressure distribution; square shims may require stricter torque control.
• Stress concentration: Square shims have four corners where stress may concentrate, while round shims have circumferential edges for more uniform stress distribution.

Etching processing removes unwanted parts with a corrosive solution, suitable for medium volume production (several hundred pieces). Etched shims are free of burrs and deformation, with high precision. This method doesn't require expensive fixtures, effectively reducing initial costs.

The process involves applying photoresist to metal material, masking, light exposure to sensitize unmasked areas, then etching exposed metal. Finally, residual resist is removed, cleaned and dried.

Basic knowledge: Stainless steel is an alloy material with corrosion resistance, composed mainly of iron, chromium and nickel. These elements resist oxidation and corrosion, providing durability and aesthetics.

• Cleaning: Use mild detergents and soft cloth; avoid acidic/alkaline components. Rinse with water and dry with clean soft cloth.
• Stain remover: For stubborn dirt, use special stainless steel stain remover following product instructions. Alcohol or vinegar can also be effective.