Start by matching the inner diameter to the rod diameter with a small clearance to allow proper seating. The outer diameter should provide enough bearing surface to distribute load, and the washer thickness should balance clamping force with the risk of bending. For simple use, a flat washer is common; if you need to prevent loosening, consider a lock washer or a shoulder washer to maintain spacing. Finally, pick a material suitable for the environment, such as stainless steel for moisture or salt exposure or zinc-coated steel for general use.

Material and hardness are the most critical factors for performance. Choose stainless steel or carbon steel based on corrosion resistance and strength; ensure the hardness is sufficient to resist deformation but not so hard that it damages the rod, and consider coatings or plating to improve wear or corrosion resistance. Also avoid mixing dissimilar metals in humid environments to reduce galvanic corrosion.

Beginners typically use a standard flat washer for straightforward seating, while professionals select specialized options like lock washers, shoulder washers, or washers with spacers to control play and alignment, and they verify fit with careful hand fitting and appropriate torque.

Inspect washers for deformation or corrosion and replace if damaged. Ensure the washer material is compatible with the rod material to avoid galvanic corrosion, keep mating surfaces clean and free of burrs, and apply lubricant if the setup requires it. Avoid over-tightening to prevent bending or damage.

Start by checking inner diameter to fit the rod with a small clearance, and choose an outer diameter that provides adequate bearing area. Select thickness based on load and required hold, and decide between metric and imperial sizes. Inspect the washer for flatness and burrs before use, and consider a washer with locking features or a shoulder design for rotating or high-precision applications.