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Sinsun Washers:Stop Loosening & Leaking
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Your Assembly's First Line of Defense: Precision Washers Engineered by Sinsun
Every bolt, screw, and nut connection is only as strong as its washer. Discover how Sinsun's full range—from standard steel and flange washers to sealing rubber washers—distributes load, seals out moisture, dampens vibration, and prevents corrosion to ensure your structures and machinery last.
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Multi-Type Washers for Every FastenerDescription
Each designed to distribute pressure, resist vibration, and extend fastener life. Available in multiple sizes, they’re a must-have accessory for secure, long-lasting fastener installations.
Washer Type |
Typical Standard |
Key Dimensions (Metric) |
Common Material / Finish |
Primary Function |
Flat Washer |
ASME B18.22.1, ISO 7089 |
ID (Inner Diameter): M3 to M30 |
Low Carbon Steel (Zinc Plated), SS 304/316 |
Distribute load, protect surface. |
OD (Outer Diameter): 2x to 2.5x ID | ||||
Thickness: 0.5mm to 5mm (varies with size) | ||||
Split Lock Washer |
ASME B18.21.1, DIN 127 |
ID: M4 to M20 |
Spring Steel (65Mn), Zinc or Plain Finish |
Prevent loosening via spring tension. |
OD: ~1.6x to 2x ID | ||||
Thickness (Wire Dia): 0.8mm to 3mm | ||||
Internal Tooth Lock Washer |
ASME B18.21.1, DIN 6798 |
ID: M3 to M12 |
Hardened Steel, Zinc Plated |
Resist rotation via teeth biting into nut. |
OD: ~1.8x to 2.2x ID | ||||
Tooth Height: 0.3mm to 0.8mm | ||||
Fender Washer |
SAE J1123 |
ID: M4 to M12 |
Low Carbon Steel (Zinc), SS 304 |
Large bearing surface for thin materials. |
OD (Large): 20mm to 50mm | ||||
Thickness: 1mm to 2.5mm | ||||
Neoprene Washer |
Non-standard; by ID/OD/Thickness |
ID: M4 to M20 |
Neoprene Rubber (60-70 Shore A) |
Seal against water/dust, dampen vibration. |
OD: Typically 5-10mm > ID | ||||
Thickness: 1.5mm, 3mm common | ||||
Nylon Flat Washer |
Non-standard; by ID/OD/Thickness |
ID: M2 to M12 |
PA66 Nylon (Natural/Black) |
Electrical insulation, corrosion-resistant spacer. |
OD: ~2x ID | ||||
Thickness: 0.5mm to 3mm |
Important Notes on Measurement:
ID (Inner Diameter): It should be a little bigger than the nominal diameter of the bolt or screw to fit well.
OD (Outer Diameter): This is the part that can hold weight.
Thickness: This is very important for getting the right amount of clamp load and seal compression.
This table is not meant to be exact. If you want to know the exact specifications, certified test data, and custom dimensions of Sinsun products, please ask for the official product data sheet or get in touch with our technical sales team.
washers for bolts
● Sinsun washers for bolts are designed to handle high clamp loads in structural and mechanical joints. Our standard flat and heavy-duty washers, which range in thickness from 1.5mm to 6mm, evenly distribute pressure to stop bolt heads from embedding and damaging surfaces. They keep machinery, steel frameworks, and car parts safe, maintaining joint stability regardless of stress or vibration.
washers for screws
● Sinsun washers for screws are made to be accurate and provide a stable bearing surface in everything from electronics to cabinets. Various sizes of these washers are available from #2 to M8 and prevent wood and plastic from being damaged by the screw head. They are an easy and cheap way to make any screwed connection last longer and look more professional.
washers for faucets
● Sealing washers are an important part of faucets. They prevent water from leaking at connection points. They are typically made of 2- to 3-millimeter-thick EPDM or reinforced rubber. When water pressure is applied, the washers compress to form a watertight seal. Plumbers and DIY plumbers use these washers under faucet bases, between fittings, and inside valve cores to ensure plumbing systems function properly and don't leak.
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Q: Do washers always go with nuts and bolts?
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A: Washers aren't always necessary, but they are highly recommended for most uses of nuts and bolts. They spread the load of the clamp so that the surfaces don't get damaged, they keep metals that are different from each other from corroding, and they make sure that the torque readings are more consistent. Not doing them can cause joints to fail, especially in softer materials.
Q: Are wave spring washers better than flat washers?
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A: Wave washers should be used when there is vibration in a small space where there isn't much room to move. They have a lower, more even spring force due to their wavy shape and have a better performance than flat washers, even after a long period of use. So they are perfect for electronic and aerospace assemblies where smooth, even pressure distribution is very crucial.
Q:What are the benefits of silicone washers compared to EPDM?
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A: Unlike EPDM rubber, Sinsun silicone washers perform well in extreme temperatures (-60°C to 230°C). Silicone washers have good flexibility at low temperatures and they are stable at high temperatures, which makes them a good choice for automotive engine compartments, air conditioning systems, and food-grade containers. However, EPDM rubber typically offers better cost-effectiveness.
Q: Can flat rubber washers be used to seal oil or fuel?
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A: Don't use standard flat rubber washers made of materials like EPDM for oil or fuel. These liquids break down most types of rubber. Sinsun makes washers out of fuel-resistant materials like Viton (FKM) or Nitrile (NBR) for use in automotive and industrial fluid systems.
Q: Why are stainless steel nuts and bolts used for outdoor projects?
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A:: When you are working on an outdoor project, you should use stainless steel bolts and nuts (usually 304 or 316 grade). Whether it's rain, humidity, or salt spray, they'll remain durable and aesthetically pleasing even under harsh conditions. Always pair them with stainless steel flat washers to prevent electrochemical corrosion.
Q: What does an internal tooth lock washer do?
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A: The teeth on an internal tooth lock washer point inward. The sharp teeth dig into the bolt or screw head and the joint's bearing surface when tightened. The biting action makes it very difficult for vibrations to loosen rotating items, such as motors, pumps, and heavy equipment housings.
Q:Which types of lock washers should I use and when?
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A: Lock washers have the following types:
Split Washers: cheap and good at stopping vibrations.
Internal and external tooth lock washers are used in places where there is a lot of vibration and they bite into surfaces.
Belleville/Conical Spring Washers: For holding heavy loads and keeping tension in bolted joints.
Tab Washers: These are used when safety is very important, and a tab is bent to keep the nut in place. You should think about how much weight you can carry, how much vibration you can handle, and how safe you want the product to be.
Q: What is the purpose of a conical spring washer?
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A conical spring washer, also known as a Belleville washer, is made to support very heavy loads with little bending. For example, turbine flanges, large presses, and important structural connections are all places where it is used to keep preload in bolted joints that are likely to expand, vibrate, or relax under stress. You can stack them to change the spring rate.
Q: When should you use a tab washer?
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A tab washer is the best choice for connections that are not permanent and need to be completely protected from rotation. The tabs of the nut bend up against the flats of the nut and the component after it is tightened. This kind of physical locking can be seen and is often used in aviation, racing, and high-speed machines.
Q: Is it necessary to use roof screws with washers?
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A: Roof screws with washers (especially those with EPDM or rubber washer) are very important for creating a waterproof, weather-resistant seal on roofing materials. The washer contracts when compressed, effectively preventing rainwater from seeping around the screw shaft. When they are used with screws, they prevent leaks, wood rot, and insulation damage.
Q: Is it okay to use a regular spring lock washer in a place where it gets hot?
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A: No, a regular carbon steel spring lock washer will lose its temper (and thus its spring force) at high temperatures, usually above 250°C. You need to use a washer made of a material that can handle high temperatures, like Inconel or a stainless steel version that has been heat-treated.
Q: What is the square hole in a carriage bolt washer for?
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A: The specific carriage bolt washer, which is usually a square or rectangular plate, is made to fit into the square neck under the head of a carriage bolt. This stops the bolt from turning when you tighten the nut on the other side. This is very important when you can only get to one side of the assembly, like when you are framing wood.
Q: What is a disc washer?
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A: A disc washer is often the same thing as a regular flat washer. However, in some situations, it can mean a thicker, more precisely ground flat washer that is used as a spacer or with other parts, like a conical spring washer in a stacked assembly, to change how the spring works.
Q: When would I need thick washers?
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A: You need thick washers mostly as spacers to fill in extra space on a bolt shank, which makes the "grip length" shorter. This is helpful when the bolt is too long for the material being fastened, when you need to line up parts, or when you need to raise a nut or bolt head above a surface.
Q: What is the purpose of a hardened washer?
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A: You need hardened washers (usually heat-treated to HRC 40–50 or higher) when there is a lot of weight on them or when you are using high-strength bolts (Grade 8 or higher). They keep the washer from bending or "dishing out," which would make the clamp load on the joint weaker and could break the fastener.
Q: Can you use metric washers instead of SAE washers?
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A: Metric washers and SAE (Imperial) washers can't usually be used instead of each other because their inner and outer diameter standards are different. A 3/8" SAE washer fits a 3/8" bolt, and a 10mm metric washer fits an M10 bolt. If you mix them up, they may not fit correctly or work as well.
Q: Why is a teeth washer better at locking than a split washer?
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A teeth washer (internal or external tooth lock washer) locks things up better than a split washer because it makes a positive mechanical lock. Sharp teeth dig into the workpiece and fastener, so they cannot turn. Split washers rely on spring tension and friction to work, but strong vibrations can break them.
Q: Where would I use large rubber washers?
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A: You would use big rubber washers anywhere you need a wide surface to seal or dampen. It can be used to seal large pipe flanges, prevent vibration of mechanical supports, prevent moisture from penetrating access ports, or protect large fixed installations from scratches.
Q: What is the square hole in a carriage bolt washer for?
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A: The specific carriage bolt washer, which is usually a square or rectangular plate, is made to fit into the square neck under the head of a carriage bolt. This stops the bolt from turning when you tighten the nut on the other side. This is very important when you can only get to one side of the assembly, like when you are framing wood.
Q: What grade should the most important parts of the suspension be?
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A: Sinsun's Class 10.9 Bolt fasteners are made to hold up under heavy, moving loads in cars and machines. They can hold at least 1040 MPa of tension.
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