Lag screw
Shear Strength Tested to 3,200 lbs
No Bending. No Breaking.No Rusting
Our Threads Grip Where Others Strip
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Sinsun Lag Screws: The Foundation for Your Most Demanding Projects
Sinsun lag bolt (screws) are designed for critical wood-to-wood and wood-to-concrete connections. Explore the engineering behind their superior holding power and shear strength.0.60" Thick Shank. For When Friction Isn't Enough.
Get a Quick Qoute
A. The Hex-Head Drive-Maximum Torque Transfer
"Sinsun's hex head lag screw unique hexagonal drive design ensures 100% torque transfer and eliminates slippage. It allows for direct drive without pre-drilling, fundamentally solving the problems of Phillips head screws easily cam-out and stripped threads.
Direct drive using a socket wrench or impact wrench makes operation simple and quick, increasing installation speed by over 30%.
Up to 80 ft-lbs torque capacity provides tremendous clamping force on screws. Designed for heavy-duty applications."
B.The Shear-Resistant Shank-Engineered to Resist Bending
"Eliminate Shear Failure: The Sinsun shank is specifically engineered to resist the powerful sideways (shear) forces that cause standard screws to bend and fail, ensuring your structure remains intact under stress.
30% Higher Load-Bearing: Its robust design provides superior support, capable of handling over 30% higher load capacity without deformation—crucial for framing and heavy-duty structural applications.
Built to Last 15+ Years: By effectively resisting bending, Sinsun screws maintain connection integrity long-term, eliminating the risk of costly repairs or callbacks due to joint failure."
C. The Cutting Tip & Aggressive Threads-Self-Starting Penetration & Deep Grip
"The Sinsun sharp cutting tip bores its own path, eliminating the drilling step. This cuts installation time by up to 50% for immediate starts in wood and composite materials.
Faster Driving with 30% Less Effort: Our aggressive, deep threads clear material quickly, reducing friction and binding. This allows the screw to sink faster with less strain on tools.
The deep, sharp threads create a wider bite path, maximizing pull-out resistance. This ensures a 40% stronger hold for connections that stay secure under heavy load."
D.The Material & Finish-Built-In Corrosion Defense
"Sinsun's advanced galvanized coating withstands over 500 hours of salt spray testing, offering 2X the corrosion resistance of standard finishes for long-term reliability.
3-Tier Defense for All Environments: Choose the right protection: Black for general use, Galvanized for damp conditions, and Stainless Steel for severe, corrosive environments.
The built-in corrosion defense ensures structural integrity for over 15 years, preventing rust-related failures and saving you from expensive repairs and maintenance callbacks."
stainless steel lag screws
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deck lag screws
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eye lag screws
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black lag screws
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construction lag screws
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structural lag screws
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concrete lag screws
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galvanized lag screws
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self tapping lag screws
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steel lag screws
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hook lag screw
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heavy duty lag screws
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long lag screws
Send inquiry NowStructural Lag Screws High Tensile
Our high-tensile lag screws are engineered for heavy-load wood assemblies worldwide. Thick, rugged threads prevent pull-out, with rust-proof plating for harsh outdoor/indoor conditions. Perfect for securing joists, posts and heavy timber, easy to install with standard tools for professional builds.
Diameter |
Length |
Material Grade |
Finish |
Common Applications |
1/4" |
1"-3" |
Grade 2 |
Zinc Plated |
Light-duty furniture assembly, small outdoor projects |
5/16" |
3"-6" |
Grade 5 |
Hot-Dip Galvanized |
Deck construction, ledger board attachment |
3/8" |
4"-8" |
Grade 5 |
Zinc/Yellow |
Structural timber framing, playground equipment |
1/2" |
6"-12" |
Grade 8 |
Hot-Dip Galvanized |
Heavy construction, beam connections |
5/8" |
8"-16" |
Grade 8 |
Hot-Dip Galvanized |
Commercial construction, marine applications |
Lag screws for wood
For wood applications, specify Sinsun's 5/16" or 3/8" diameter lag screws. The self-tapping tip eliminates pre-drilling in most lumber, while the corrosion-resistant coating withstands outdoor elements. From securing deck ledgers to fastening timber frames, these screws provide reliable shear strength where standard fasteners fail.
Lag screws for ledger board
Sinsun hot-dipped galvanized lag screws are the trusted choice for securing ledger boards to wooden framing. Engineered for exceptional shear strength and corrosion resistance, these heavy-duty screws, like the 3/8" x 4" size, install faster than bolts and create a rock-solid foundation for your deck. Ensure a lasting, secure connection for your outdoor project with Sinsun.
Lag screws for metal
Sinsun's self-drilling lag screws for metal feature a drill-point tip that cuts through steel without pre-drilling. Made from high-grade steel with a corrosion-resistant coating, they provide a fast, rock-solid fix for attaching wood to metal framing, purlins, or beams.
Lag screw for tv mount
Sinsun's heavy-duty lag screws, like a 1/4" x 3" size, are engineered for TV mounts. They bite deep into wooden wall studs, providing the extreme shear strength needed for a secure, wobble-free installation. Trust your valuable electronics with Sinsun.
Eye lag screws for drop ceiling
Sinsun's 1/4" x 3" eye lag screws feature a forged eye and a sharp point for easy start. They install directly into overhead wood joists, providing a solid and reliable anchor point for your drop ceiling grid—no pre-drilling needed for a secure hang.
Coach screws for concrete
For concrete applications, use Sinsun's 1/2" diameter concrete lag screws with corrosion-resistant coating. These screws install directly into concrete without anchors, providing 750 lbs of pull-out resistance - ideal for securing structural framing to foundation walls.
Don't just take our word for it. Read reviews from contractors and DIYers worldwide who rely on SINSUN lag screws for critical structural projects. Discover how our deep-threaded grip and anti-corrosion coating deliver lasting performance on job sites from Europe to North America.
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Q: What is the main difference between a Lag Screw and a Log Bolt?
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A: The main difference is how they are installed and their purpose.
A Lag Screw is like a giant, heavy-duty wood screw. It is threaded along most of its length and is designed to be driven directly into wood or a pre-drilled pilot hole. It holds things to wood (e.g., fastening a metal bracket to a timber).
A Log Bolt (or Through Bolt) is used to connect two pieces of wood together. It is a fully threaded rod that passes through a pre-drilled hole in both pieces of wood and is secured on the other side with a nut and washer. This creates a very strong, clamped connection.
Q: What is the proper way to install a lag screw into wood?
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A: To prevent wood from splitting and ensure a strong hold, always pre-drill a pilot hole. The pilot hole's diameter should be slightly smaller than the screw's shaft (not the threads). For heavy loads or hardwoods, also drill a wider clearance hole through the first piece of wood and use a washer under the head to distribute the force.
Q: What is a flat head or countersunk lag screw used for?
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A: These screws are designed to be driven flush with or below the wood surface. This creates a smooth, clean finish, which is crucial for:
Safety: Preventing snagging on clothes or skin.
Aesthetics: Creating an invisible fastening point.
Function: Allowing another piece of material to sit flat against the surface.
Q: What are the most common uses for a lag screw?
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A: Lag screws are the go-to fastener for heavy-duty, wood-to-wood, or metal-to-wood connections. Common uses include:
Building decks (ledger boards to house framing).
Securing rafters and joists.
Attaching large hardware like gate hinges.
Constructing timber frames and pergolas.
Q: I've heard of "leg screws" for furniture. Is this the same as a lag screw?
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A: While sometimes used colloquially for furniture assembly, "leg screw" is not a standard industrial term. It often refers to a specific type of fastener used in furniture, which may be a machine screw that threads into a metal insert, not into wood directly. A true lag screw is much heavier-duty, has a coarser thread, and is designed to be driven directly into wood to support very high loads.
Q: What are square head lag screws used for?
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A: Square head lag screws offer excellent grip for a wrench, making them ideal for high-torque applications where you need to pull components together tightly. They are common in traditional timber framing and restoration work. Their main advantage is that they are less likely to strip than hex heads when using extreme force with a spanner.
Q: What is a 1 1/4" lag screw typically used for?
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A: A 1-1/4 inch lag screw is a relatively short fastener. It's perfect for light-duty applications where you don't need deep penetration, such as:
Attaching thin brackets.
Fastening hardware to a wooden door or frame.
Small DIY projects where a longer screw would poke through the other side.
Q: Do I always need a washer with a lag screw?
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A: Yes, it is highly recommended. A washer (typically a flat washer) serves two critical purposes:
Distributes Pressure: It prevents the screw head from digging into and crushing the wood, which maintains the clamp force.
Prevents Pull-Through: It provides a larger bearing surface, making the connection stronger and less likely to loosen under vibration or load.
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