What are washers?

Washers are thin, typically metal plates placed between a fastener, such as a screw or bolt, and the material being joined.
Their primary function is to prevent loosening. Common types include plain washers and spring washers.

Plain Washers

・Increase the bearing surface area of the fastener, distributing pressure and reducing stress on the mating surface.
・Minimize the risk of surface sinking and subsequent loosening, especially when used with soft materials or small contact areas.
・Protect the fastened object from damage, preventing scratches and rotational marks around the screw hole.

NBK offers an extensive selection of plain washers, catering to diverse application needs.

Spring Washers

・Feature a split and helical design, providing spring tension to resist loosening caused by vibration or movement.
・Typically used in conjunction with bolts and nuts to maintain joint integrity.

Key Benefits of Using Washers

・Enhanced joint security and reduced risk of loosening.
・Protection of the fastened material from damage.
・Improved load distribution and stress reduction.

Why Choose NBK Washers?

NBK provides a wide range of plain washers designed for optimal performance and reliability.
Our products are engineered to meet the demands of various industrial applications, ensuring secure and durable fastening solutions.

Washer Types: Unique Solutions from NBK

NBK offers a diverse range of specialized washers designed to address specific engineering challenges.
We provide solutions beyond standard washers.

Adjusting Washers

・Precision-engineered washers designed with dimensions deviating from standard JIS/ISO specifications.
・Optimized for precise height adjustments and prevention of seating surface sinking.
・Ideal for securing connections in elongated holes and materials with low surface pressure resistance, such as aluminum and resin.
・Functions as a collar or spacer, enabling fine-tuning of assembly tolerances and cumulative error adjustments.

SWA-AW (Steel - Ferrosoferric Oxide Film)
SWA-AWEL (Steel - Electroless Nickel Plating)
SWAS-AW (Stainless Steel)
SWAS-AWBK (Stainless Steel Black)

Spherical Washers: Precision Alignment for Enhanced Performance

・Misalignment Absorption: Designed to compensate for angular deviations between bolts and seating surfaces.
・Unique Spherical Interface: Features a specialized convex/concave spherical contact surface between two washers.
・Tilt Compensation: Effectively accommodates bolt and seating surface tilts. (SQW series supports up to 2°, SQWS series up to 3°).

SQW (Stainless Steel)
SQWS (SUS304)

Retaining Washers: Secure Fastening and Loss Prevention

・Simplified Screw Retention: Prevents accidental screw drop and loss by easily integrating with standard commercial screws.
・Reliable Thread Engagement: Integrated washer hooks firmly grip thread peaks, ensuring robust retention even after repeated assembly.
・Ideal for Frequent Access Panels: Specifically designed for protective and inspection covers that require frequent removal and reinstallation.
・CE Marking Compliance: Facilitates adherence to CE Marking requirements for product safety and conformity.

SWAS-SC
SSC-SET

Seal Washers: Leak-Proof Fastening Solutions

・Integrated Rubber Seal: Features a built-in rubber seal for reliable fluid and gas containment.
・Prevent Leakage: Effectively seals the interface between the screw head and the bearing surface, eliminating leaks.
・Material-Specific Performance: Operating temperature and sealing properties vary based on the rubber packing material, ensuring application-specific compatibility.

SWS (Rubber Packing Material：NBR)
SWS-F (Rubber Packing Material：Fluoro-rubber)
SWS-E (Rubber Packing Material：EPDM)
SWS-S (Rubber Packing Material：Silicone rubber)
SWS-HFT (Rubber Packing Material：Fluoro-rubber, PFA Coating)

High-Strength Stainless Steel Washers: Engineered for Demanding Applications

・Enhanced Hardness: Achieves a hardness of 300 HV or greater, exceeding that of standard stainless steel plain washers.
・Optimized for High-Tensile Bolts: Specifically designed for use with stainless steel bolts exhibiting tensile strengths ranging from 800 N/mm² to 1000 N/mm². *¹
・Seamless Integration: Ideal for pairing with high-strength stainless steel hex socket head cap screws, such as NBK's SNSLG, SNSX-88, or SNSX-109 series.
・Superior Corrosion Resistance: Fabricated from 316L Stainless Steel, ensuring exceptional resistance to corrosive environments.

  *¹： Plain washer hardness categories and compatible fasteners are defined by JIS B 1256, "Plain washers."

SWALG-F

Eccentric Lock Washers: Simplified Vibration Resistance for Secure Fastening

・Anti-loosening effect : Using with standard hexagonal nuts to prevent screw loosening.
・Simplified Installation: Allows initial hand-tightening of the hex nut, streamlining the mounting process until locking force is engaged.
・Proven Performance: Successfully passed the rigorous NAS vibration test (NAS3350) and demonstrated exceptional loosening-prevention capabilities in the Junker vibration test. ＞＞Details available here

SWAS-EW

Recommended Washer Mounting Sequence

For optimal performance and joint integrity, the typical mounting sequence is: spring washer followed by plain washer.

Washer Dimensions: Adherence to Industry Standards

Washer dimensions are standardized according to various industry specifications, including JIS and ISO.

For detailed information on dimensions governed by JIS standards, please refer to the following resources:

Plain Washer Dimensions/Shapes (JIS B 1256:2008)
Spring Washer Dimensions/Shapes (JIS B 1251:2018)

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