Washers

What are Washers?

Washers are thin discs with a center hole used under a nut or bolt head to spread load, protect surfaces, support consistent torque, and in some cases seal against fluids or resist loosening.

Do you need washers for screws?

Often yes. Washers help on soft materials and anywhere you want better load spread or surface protection. Some screws have built-in flanges or features that reduce the need, but a simple flat washer is still useful in many installs.

• Soft materials such as wood, plastics, and drywall benefit from a washer under the head
• Enlarged or irregular holes are easier to bridge with a larger outside diameter
• Where vibration is present, choose a lock style or add a separate locking method

What types of washers are there?

• Flat washers for load distribution and surface protection
• Lock washers split or toothed styles that add resistance to rotation
• Fender washers extra large outside diameter to cover big or slotted holes
• Sealing washers metal backed with an elastomer to help prevent leaks
• Conical and cup styles spring action to help maintain preload
• Square and specialty shapes for channels, timber, or specific hardware

What size washer do I need? inch and metric

• Match the nominal washer size to the fastener size such as 1/4 in or M6
• Verify the inner diameter fits the shank without binding
• Choose the outside diameter and thickness for the load you need to spread
• Select standard, wide, or fender patterns based on hole size and clearance

Which washer material should I choose

18-8 and 304 stainless steel

General purpose corrosion resistance with a clean appearance for indoor and light outdoor use.

316 stainless steel

Preferred for marine, salty, or chemically harsh environments; pair with 316 hardware when possible.

Zinc plated steel

Economical for dry interiors with light corrosion protection.

Hot dip galvanized steel

Thick zinc layer for outdoor structural work; match with galvanized bolts and nuts.

Brass and silicon bronze

Conductive and corrosion resistant choices used in electrical and marine applications.

Aluminum

Lightweight with natural corrosion resistance; consider galvanic compatibility in mixed-metal joints.

When should I use a lock washer

Use a lock washer when movement or vibration could loosen the joint. Split and tooth styles add bite. For severe vibration, consider wedge-lock pairs or a liquid threadlocker.

How do I install washers correctly

• Place the washer under the rotating part, either the nut or the bolt head
• Keep bearing surfaces clean and flat for consistent preload
• Avoid over-torque on sealing types to protect the elastomer
• Re-check torque after initial run-in if soft materials compress

Washers vs alternatives what should I know

Washers help with load spread, surface protection, and in some cases sealing or anti-rotation. They do not replace good joint design. For high vibration or safety critical assemblies, add a locking feature or choose hardware designed to resist back-off.

Washer Specifications

AN960C Washer Specifications

Stainless Steel Extra Thick Flat Washer Specifications

NAS Washer Specifications