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.

Key Differences:

• 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 (steel, copper, aluminium, rubber, silicone, etc.), selected based on working conditions.
• Installation effect: Round gasket edges distribute stress more uniformly; square gaskets may concentrate force at corners.
• Torque control: Easier with round shims due to uniform pressure distribution; square shims may require stricter torque control.
• Stress concentration: Square shims may experience stress concentration at corners compared to round shims.

Punching processing is a method using special dies for cutting, suitable for mass production due to short processing time per part. The process uses press equipment. For production over 1,000 shims, die blanking is more cost-effective despite higher initial costs. This method is not suitable for small batch production. Burrs from blanking may require additional treatment.

Carbon steel is a common metal material with several advantages:

• High strength: Excellent strength characteristics suitable for construction, automotive, and aerospace applications.
• Good wear resistance: Ideal for tools, machine parts, and industrial equipment.
• Strong plasticity: Easy to process and form through various working processes.
• Price economy: Competitive cost advantage for large-scale industrial applications.

Disadvantages:

• Corrosion tendency: Requires corrosion protection treatments or coatings.
• Low shock resistance: May deform under vibration compared to high-strength alloys.

Galvanising is a surface treatment plating zinc for rust-resistant appearance. Zinc color is silver-white; passivation can produce white, colored, or army green finishes.