Screw Washers
Eliminate screw loosening in harsh working conditions.
Distribute load evenly to protect component surfaces.
Durable screw washers for long-term industrial use.
Sinsun Screw Washers | Custom Industrial Fastener Washer Solutions
Need reliable screw washers for vibration resistance and surface protection? Sinsun supplies DIN/ASME flat washers, lock washers, and sealing washers. Factory pricing with global export. Request a quote today.
Get a Quick QouteSinsun Screw Washers – Precision Flat, Lock & Specialty Washers for Industrial Fastening
Shop premium Sinsun screw washers in diverse sizes & materials. Manufactured for vibration resistance, load distribution & surface protection. Ideal for automotive, construction & machinery industries. Get bulk OEM quotes now.
Get a Quick QouteReliable Screw Washers – Definition, Industrial Uses & Sinsun Advantages
Screw washers are the flat ring-shaped fastening parts between screw heads and jointed workpieces and are the main auxiliary parts of the mechanical fastening system. Screw washers spread loads, prevent loosening, reduce friction, and protect surfaces. They solve common industrial problems such as localised pressure damage, screw loosening, and component wear during equipment operation. These universal fastener accessories are suitable for most specifications of screw connections and are essential for stable mechanical assembly.
Sinsun screw washers are not like other washers on the market. They have even thickness, smooth without burr, and accurate inner and outer diameter tolerances, ensuring perfect matching with general and non-general screws.
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Spring Lock Washers
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serrated washers
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Belleville Spring Washers
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Fender Washers
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Rubber Sealing Washers
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Square Washers
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nylon washers
Send inquiry Now| Screw Size (M) | Inner Diameter (d₁) mm | Outer Diameter (d₂) mm | Thickness (s) mm |
| M2 | 2.2 | 5 | 0.3 |
| M2.5 | 2.7 | 6 | 0.5 |
| M3 | 3.2 | 7 | 0.5 |
| M4 | 4.3 | 9 | 0.8 |
| M5 | 5.3 | 10 | 1 |
| M6 | 6.4 | 12 | 1.6 |
| M8 | 8.4 | 16 | 1.6 |
| M10 | 10.5 | 20 | 2 |
| M12 | 13 | 24 | 2.5 |
| M14 | 15 | 28 | 2.5 |
| M16 | 17 | 30 | 3 |
| M20 | 21 | 37 | 3 |
| M24 | 25 | 44 | 4 |
| M30 | 31 | 56 | 4 |
| M36 | 37 | 66 | 5 |
| M42 | 43 | 78 | 6 |
| M48 | 50 | 90 | 6 |
| M56 | 58 | 100 | 8 |
| M64 | 66 | 115 | 9 |
| Screw Size | Inner Diameter (in) | Outer Diameter (in) | Thickness (in) |
| #2 | 0.098 | 0.236 | 0.02 |
| #4 | 0.125 | 0.281 | 0.025 |
| #6 | 0.149 | 0.312 | 0.032 |
| #8 | 0.174 | 0.375 | 0.04 |
| #10 | 0.199 | 0.437 | 0.04 |
| 1/4" | 0.281 | 0.625 | 0.051 |
| 5/16" | 0.343 | 0.688 | 0.064 |
| 3/8" | 0.406 | 0.812 | 0.064 |
| 7/16" | 0.469 | 0.922 | 0.08 |
| 1/2" | 0.531 | 1.062 | 0.08 |
| 9/16" | 0.594 | 1.156 | 0.088 |
| 5/8" | 0.656 | 1.312 | 0.1 |
| 3/4" | 0.812 | 1.469 | 0.1 |
| 7/8" | 0.938 | 1.75 | 0.12 |
| 1" | 1.062 | 2 | 0.125 |
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Material Grades: Carbon Steel (4.8–12.9), Stainless Steel 304/316, Spring Steel 65Mn, Brass, Nylon.
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Surface Finishes: Plain (Oil), Zinc-Plated (Blue/White/Yellow), Black Oxide, Phosphate, Hot-Dip Galvanized, Dacromet, Geomet.
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Hardness Range: Flat Washers HRC 30–45; Spring Washers HRC 40–50; Serrated Washers HRC 35–48.
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Standards Met: DIN 125A / DIN 127 / DIN 7980 / DIN 6797 / DIN 6798; ISO 7089 / ISO 7090; ASME B18.21.1 / ASME B18.22.1.
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Torque Guidelines (Reference): M6 → 8 ft·lbs (10 Nm); M8 → 20 ft·lbs (25 Nm); M10 → 35 ft·lbs (45 Nm); M12 → 60 ft·lbs (80 Nm) for grade 8.8 assemblies under standard lubrication.
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Operating Temperature Range: Stainless Steel (-200°C to +550°C); Carbon Steel (-50°C to +300°C); Nylon (-40°C to +120°C); Neoprene Rubber (-30°C to +120°C)
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📐 Dimensional drawings and 2D/3D CAD files for all standard and custom washer configurations are available upon request. Contact our technical support team for immediate access.
Discover where Sinsun screw washers excel—from heavy machinery and automotive to construction, marine, and renewable energy systems. We engineer washers for every challenging environment.
Heavy Machinery & Industrial Equipment Vibration Control
- Fasteners that won’t shake loose under constant vibration are needed for vibrating screeners, mining conveyors, rock crushers and large presses. Sinsun spring lock washers and serrated washers offer constant clamping force under dynamic loading. The 65Mn spring steel keeps its elasticity for thousands of vibration cycles without permanent deformation. External toothed washers, recessed into the bolt head and the bearing surface, ensure no rotation, providing extreme shear-force connections. That's why heavy equipment manufacturers all over the world specify Sinsun for gearbox mounting, motor bases and conveyor frame bolting.
Assembly of Automotive Chassis and Engine Components
- Fastener Punishing Environment: Under-Bonnet Temperatures, Fluid Exposure and Road Vibration. Sinsun provides automotive-grade spring washers and flat washers with yellow zinc or Dacromet coating for salt spray, engine oil and temperature resistance from -30°C to +150°C. Our washers are used in suspension mounting points, engine cradle bolts, exhaust flanges and gearbox housing fasteners. Tight inner diameter tolerance ensures correct fitment on OEM fasteners with no binding or excessive play. Manufactured to IATF 16949 compliant manufacturing processes for the automotive supply chains.
Structural Steel Construction & Prefabricated Buildings
- Washers are used in steel building frames, prefabricated modules and crane runway connections to spread high preload forces without crushing structural members. Sinsun extra large square and round washers to increase bearing area to prevent local yielding of steel members under bolt tension. Our hot-dip galvanised flat washers are ASTM F436 compliant for structural bolting and are corrosion resistant for outdoor or coastal construction. For slip critical connections where it is critical to maintain bolt preload we recommend our hardened washers with Grade A325 or A490 bolts. Trusted by prefabricated building manufacturers and steel erectors in international markets.
Marine, Offshore & Coastal Infrastructure
- Salt water exposure causes standard fasteners to deteriorate quickly, leading to galvanic corrosion and bolt head seizure. Sinsun marine grade screw washers are manufactured in stainless steel 316L (A4) with higher molybdenum content for better resistance to pitting corrosion. Our rubber-sealing bonded washers stop water ingress through the fastener holes in the hulls of aluminium boats, jetty gangways and offshore platform handrails. Nylon insulating washers to avoid the galvanic corrosion risk for electrical isolation between stainless bolts and aluminium structures. These washers meet the material standards of ISO 3506-1 for marine grade fasteners and are suitable for direct salt water splash environments.
Furniture Manufacturing & Woodworking Assembly
- Driving screws straight into softwoods, particleboard and medium-density fibreboard (MDF) will split panel edges and ruin finished surfaces. Sinsun flat and finishing washers help distribute the load of the fastener over a wider area to prevent breakout and surface damage. Our square washers are designed to offer anti-rotation properties in routed channels or blind slots in furniture frames. For knock-down (KD) fittings and ready-to-assemble (RTA) furniture we offer finishing washers in brass and nickel plate for visible locations where looks are important. The screw heads sit flush to the surface of the washer to give it the professional premium look that retail buyers expect.
Electrical Enclosures, Switchgear & Control Cabinets
- Sensitive electronics in control cabinets require non-conductive, non-magnetic mounting solutions. Sinsun nylon flat washers and plastic shoulder washers isolate PCB standoffs from metal chassis to eliminate short circuits and ground loops. Our captive finish washers for countersunk screws provide flush-mounted hardware that won’t snag cables or inhibit airflow in tight enclosures. Neoprene sealing washers with EPDM rubber gaskets for outdoor telecommunications cabinets and EV charging stations. These sealing washers meet IP65 and NEMA 4X ingress protection standards to prevent the ingress of dust and moisture at the cable entry points.
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– Andrei Popescu, Maintenance Manager, Romania
*We switched to Sinsun spring washers after repeated loosening on our packaging line conveyors. The 65Mn steel stays springy after 6 months of continuous run time. No more nightly re-torqueing. Great product.*
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– Katarzyna Nowak, Procurement Specialist, Poland
*The neoprene sealing washers for our roofing screws arrived in perfect condition. Exactly as sampled. Customer service helped us calculate container loading to maximize volume. Shipping to Poland took only 26 days door-to-door.*
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– Hendrik van der Merwe, Civil Contractor, South Africa
*Square washers in M12 x 50mm for our timber bridge project. We needed 38,000 pieces with hot-dip galvanized finish. Sinsun delivered in 3 weeks, fully palletized with IPPC stamps. No dimensional rejects. We will repeat next season.*
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– Juan Carlos Silva, Maintenance Supervisor, Chile
*Our Chilean mining operation uses Sinsun serrated lock washers on slurry pump base plates. The teeth bite into the mounting feet—zero loosening after 4 months of 24/7 operation. Even under high lateral load. Great value vs premium European brands.*
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– Andrzej Kowalski, Operations Manager, Poland
We manufacture control cabinets for telecom towers. Sinsun nylon insulating washers and captive finishing washers arrived labeled by SKU, no mix-ups. Clear COC documents included with every master carton. Satisfied with quality control.
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– Liam O‘Connor, Production Director, Ireland
Fender washers for RV side panel attachments. The oversized OD in stainless 304 is perfect—no fiberglass cracking. Sinsun accepted our special inner diameter spec without tooling charges. This flexibility matters for custom builders like us.
Frequently Asked Questions About Screw Washers – Expert Answers from Sins
Get quick answers to common screw washer questions—size selection, material suitability, torque retention, rust prevention, and bulk sourcing. Engineering support from Sinsun.
Q: What type of screw washer prevents loosening by vibration?
A: To prevent rotation, use lock washers with teeth (internal or external teeth). For severe vibration use serrated washers and a thread locking compound.
Q: What's the difference between DIN 125 and DIN 127 washers?
A: Flat washers for load distribution DIN 127 is for split spring lock washers, which are spring tensioned to prevent loosening.
Q: Can you produce screw washer non-standard sizes?
A: Yes. Sinsun provides full OEM custom fabrication for special requirements on inner diameter, outer diameter, thickness, material and finish.
Q: In electrical applications, do you use plastic washers instead of metal washers?
A: Yes, nylon insulating washers eliminate electrical conductivity and galvanic corrosion between dissimilar metals in control panels and marine assemblies.
Q: How to choose the right inner diameter for a screw washer?
A: The inner diameter should be a tight fit to the screw shank, but free to turn. Standard ID = nominal screw size + clearance of 0.2mm to 0.4mm.
Q: What is the best surface finish for salt water corrosion resistance?
A: Washers made of hot-dip galvanised (HDG) or stainless steel 316L offer the best protection against corrosion in salt water. Dacromet and Geomet coatings are also good choices.
Q: Are Sinsun screw washers RoHS compliant and REACH compliant?
A: Yes. All of our standard finishes are RoHS and REACH environmentally compliant for export to EU and international markets.
Q: Do Belleville washers (conical) flatten out completely under full bolt torque?
A: Appropriately sized Belleville washers will flatten approximately 50% to 75% of their free height when torqued to recommended values, with spring reserve remaining for compensation.
Q: How are Sinsun screw washers packed for international transportation?
A: Poly bags, bulk cartons, master cartons on pallets with IPPC heat treatment. We also provide retail-ready blister packs and labelling to meet your needs.
Q: Do you carry ETA approved sleeve anchors for European projects?
A: Yes. For the European market, we offer sleeve anchors with CE and ETA certification. "The certifications are required for structural applications and seismic bracing systems in EU member countries. Please contact us regarding your specific project needs.
Q: Will a split lock washer damage my workpiece surface?
A: Split lock washers are cut at the ends and will scratch softer materials. Use serrated washers or flat washers with a thread locking adhesive if the surface is painted or sensitive.
Q: What is the temperature limit for neoprene rubber sealing washers?
A: Neoprene sealing washers are effective from -30°C to +120°C. For higher temperatures, use EPDM rubber or metal sealing washers only.
Q. Can I use standard flat washers with hex head self-drilling screws?
A: Yeah. Flat washers help distribute the clamping force under the hex head . This can help prevent paint damage and reduces the chance of screw pull-through on thin gauge metal.
Q: Can I get free samples before bulk order?
A: Yeah. Free screw washer samples are available for evaluation. Buyer is only responsible for the costs of international shipping courier.
Q: What hardness should spring lock washers have for Grade 10.9 bolts?
A: For Grade 10.9 assemblies, spring washers with HRC 42-48 will provide adequate spring tension and preload retention. Sinsun tests the hardness of each batch for compliance.
Q: How do I torque a bolted joint with a rubber sealing washer?
A: Tighten until the rubber seal is visibly compressed, but not flattened. Over-torqueing can cause rubber extrusion and reduce sealing performance.
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