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- 🌐 Website: www.sinsunfastener.com
- 🏭 Factory Location: Tianjin, China — Leading fastener export hub with direct sea access to Tianjin Port
- Sinsun — your global partner for square washers that won‘t spin, won’t embed, and won‘t let you down. Request free samples or a bulk quote today.
Premium Anti-Slip Structural
Square Flat Washers
Wider surface for uniform heavy load spread.
Square shape locks zero rotational shift.
Reinforce structure for long stable fastening.
Contact usSinsun Square Washers | Anti-Rotation High Load Bearing Structural Flat Washers
Professionally manufactured Sinsun square washers feature wide bearing surfaces and anti-rotation structural design. These heavy-duty flat square washers deliver superior load distribution, stable positioning and structural reinforcement for timber framing, steel structure construction, solar infrastructure and industrial heavy-load assembly projects.
Get a Quick QouteSinsun Square Washers – Premium Anti-Slip Structural Square Flat Washers for Heavy Load Construction & Industrial Fastening
Need square washers for timber construction, C-channels, or concrete flooring? Sinsun manufactures DIN 436 square washers — larger bearing surface, anti-rotation design, and heavy load distribution. Steel, stainless, and galvanized options. Factory direct. Request a quote within 24 hours.
Get a Quick QouteExplore Our Full Range of Screw Washers – Categories with High Industrial Demand
Browse Sinsun’s complete screw washer collection: DIN flat washers, split lock washers, toothed lock washers, rubber sealing washers, and more. Each type engineered for specific fastening challenges.
Square washers are a type of flat fastening components with square outer profiles and standard round inner holes, differing from conventional circular flat washers. This special geometric structure greatly increases the effective bearing area, and realises the uniform pressure dispersion for heavy-load fastening scenarios. These industrial washers are designed for structural support and anti-rotation positioning. They stabilise bolt joints and prevent fasteners from being displaced by constant mechanical pressure and vibration.
As a professional structural fastener manufacturer, Sinsun optimises the integral stamping and forming process of square washers. This is to remove the edge burrs and uneven flatness that are common in generic products. The most common square washers are made with rough cutting workmanship, which leads to stress concentration, easy deformation and unstable positioning after long-term load bearing. Every completed washer is dimensionally accurate and dimensionally flat, thanks to our one-time precision die forming and secondary flatness calibration.
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| Nominal Bolt Size (M) | Inner Diameter (d₁) min (mm) | Inner Diameter (d₁) max (mm) | Width Across Sides (a) mm | Thickness (h) mm ±0.3 | Hardness Class | Suitable Bolt Grade |
| M6 | 6.4 | 6.62 | 20 | 2.0 – 3.0 | 140 HV | ≤ 8.8 |
| M8 | 8.4 | 8.62 | 25 | 2.5 – 3.5 | 140 HV | ≤ 8.8 |
| M10 | 10.5 | 10.77 | 30 | 3.0 – 4.0 | 140 HV | ≤ 8.8 |
| M12 | 13 | 13.27 | 35 | 3.5 – 4.5 | 140 HV / 100 HV* | ≤ 8.8 |
| M14 | 15 | 15.27 | 40 | 3.5 – 4.5 | 100 HV | ≤ 6.8 |
| M16 | 17 | 17.27 | 45 | 4.0 – 5.0 | 100 HV | ≤ 6.8 |
| M20 | 21 | 21.33 | 55 | 4.0 – 5.0 | 100 HV | ≤ 6.8 |
| M24 | 25 | 25.52 | 65 | 5.0 – 6.0 | 100 HV | ≤ 6.8 |
| M27 | 28 | 28.52 | 75 | 5.5 – 6.5 | 100 HV | ≤ 6.8 |
| M30 | 31 | 31.62 | 80 | 6.0 – 7.0 | 100 HV | ≤ 6.8 |
| M36 | 37 | 37.62 | 95 | 7.0 – 8.0 | 100 HV | ≤ 6.8 |
Hardness Note: Sizes ≤M12 are available in Class 140 HV for bolts up to Grade 8.8; sizes >M12 are Class 100 HV per DIN 436 specification. Class 100 HV washers are suitable for bolts of Property Class 6.8 and below. Use Class 140 HV washers for higher bolt grades.
| Parameter | Specification |
| Standards | DIN 3570 (piping & structural supports) / ASME B18.31.5 (threaded ends) / ISO 9001:2015 |
| Bend Types | Round (semicircular), Square (90‑degree), Semi‑Round (flattened), Offset (unequal legs), Forged Top |
| Material | Carbon steel (Q235, C1022, 10B21, 35K), stainless steel (SS304 / SS316), alloy steel (40Cr, 35CrMo, SCM435) |
| Strength Grades | 4.8, 8.8, 10.9 (metric) / Grade 5, Grade 8 (imperial) / A2‑70, A4‑80 (stainless) |
| Thread Type | Metric coarse & fine; UNC / UNF inch threads; fine thread UNF available |
| Surface Finish | Hot‑dip galvanised (ASTM A153, 45‑85 µm), electro‑zinc plated (ASTM B633), black oxide, Dacromet (zinc flake), powder coating, plain |
| Leg Length | 50 mm – 500 mm (2″ – 20″) custom |
| Inside Width | 20 mm – 300 mm (0.8″ – 12″) custom |
| Rod Diameter | M6 – M36 (metric) / 1/4″ – 1½″ (imperial) |
| Thread Tolerance | 6g (plain finish), 6h (plated finish) |
| Tensile Strength (Class 8.8) | ≥800 MPa |
| Yield Strength (Class 8.8) | ≥640 MPa |
| Rolled Threads | Yes – standard on all orders (superior thread structure and torque transfer) |
Hardness Note: Sizes ≤M12 are available in Class 140 HV for bolts up to Grade 8.8; sizes >M12 are Class 100 HV per DIN 436 specification. Class 100 HV washers are suitable for bolts of Property Class 6.8 and below. Use Class 140 HV washers for higher bolt grades.
Manufacturing Standard
Strictly manufactured per DIN436 and DIN440 international structural fastener standards, meeting global engineering acceptance criteria.
Core Materials
Available in high-quality carbon steel, galvanized steel, 304 and 316 stainless steel, covering indoor and outdoor environmental demands.
Core Performance
Features ultra-wide load bearing, anti-rotation positioning, substrate protection and structural reinforcement for heavy-duty fastening joints.
Surface Flatness
Controlled within 0.08mm tolerance, eliminating warping deformation and ensuring uniform stress distribution across the whole plane.
Load-Bearing Capacity
Thickened models withstand ultra-high mechanical pressure, effectively avoiding structural collapse caused by local stress concentration.
Surface Finishes
Supports plain black finish, zinc plating, hot-dip galvanizing and passivation for diversified anti-corrosion protection.
Application Temperature
Stably works from -40℃ to 200℃, adapting to extreme temperature environments of construction and industrial equipment.
Diversified Industrial & Engineering Application Scenarios of Sinsun Square Washers
High-value application scenarios of Sinsun square washers, covering building construction, new energy infrastructure, agricultural machinery and marine structural engineering.
Marine & Offshore Structural Engineering
Sinsun stainless steel square washers are applied to structures like offshore platforms, yacht brackets and port facilities. Metal fasteners are at a high risk of corrosion in coastal salt spray and humid environments.Excellent salt spray resistance with premium stainless steel materials. Stable structural performance under harsh working conditions ensures the long-term safety and reliability of marine structural fastening joints.
Agricultural & Heavy Machinery Equipment
Sinsun square washers are used for fastening on key joints of large agricultural machinery, engineering vehicles and heavy industrial equipment. Mechanical operation causes permanent vibration and alternating loading.The rectangular anti-rotation structure can prevent bolts from loosening and the joints from shifting effectively. The high load-carrying capacity meets heavy-duty mechanical operation needs and improves equipment stability.
Infrastructure for Solar & Wind Energy
Sinsun square washers are widely used in new energy bracket systems including solar panels and wind power equipment. Outdoor open-air installation requires long-term anti-loosening stability.These washers are resistant to wind vibration and environmental erosion and keep the energy brackets in an accurate position. The anti-corrosion surface treatment can adapt to outdoor harsh weather, reducing maintenance and replacement.
Timber Frame Building & Construction
In wooden beam frames, steel keel structures, and building support brackets, Sinsun square washers are widely used as supporting accessories. The large bearing surface spreads the pressure of the bolts to avoid wood splitting and steel plate deformation.They have anti-rotation properties to fix structural bolts tightly, avoiding positional deviation caused by building micro-vibration. They improve the overall structural stability and durability of buildings' long-term operation.
Global Square Washer Customer Reviews – Real Feedback from Industrial Buyers
Real square washer reviews from buyers across Poland, South Africa, Romania, Chile, Serbia, and Australia. Sinsun delivers DIN 436-compliant dimensions, proper heat treatment, and reliable export.
Google High-Frequency FAQ for Sinsun Square Washers
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✅ Standard compliance you can trust - DIN 436:2024-10, DIN 435 (bevel), DIN 434 (U-channel), ASTM F844 — all documented.
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✅ Anti-rotation design - square shape physically prevents spinning in channels, against edges, and in slotted holes.
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✅ Larger bearing area - approximately 27% larger than round washers of same circumscribed dimension — reduces embedment into soft materials.
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✅ HDG coating expertise — 500+ hours salt spray, separation layers to prevent coating damage, thickness verification included.
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✅ Full material range — carbon steel, stainless A2/A4, nylon, brass, copper — one supplier, all your needs
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✅ Factory-direct pricing — stamping, cutting, and HDG in-house, no trading markups.
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✅ Responsive engineering support — real structural fastener specialists answer your technical questions.
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