Hex Head Wood Screw / Coach Screw (Глухарь) – DIN 571 & Lag Screw

Product Overview: The Heavy-Duty Timber Fastener

Our Hex Head Wood Screws, historically known as Coach Screws or Lag Screws (and sometimes Lag Bolts), are heavy-duty fasteners designed for connecting heavy lumber or attaching steel components to timber. Unlike standard wood screws, these feature a hexagonal head that allows for high-torque installation using a wrench or impact driver, making them indispensable in heavy carpentry and timber framing.

Manufactured strictly according to DIN 571 standards, our screws feature a coarse wood thread and a sharp gimlet point, allowing them to bite securely into both softwood (pine, spruce) and hardwood (oak, birch) without slipping.

Russian Name: Глухарь / Шуруп с шестигранной головкой / Сантехнический болт

Standard: DIN 571, ANSI/ASME B18.2.1

Engineering Design & Features

1. Hexagonal Head for High Torque

The defining feature of a Lag Screw is its hex head. Standard Phillips or Pozi drive screws often “cam out” (strip) when driving into dense wood.

• Advantage: The hex head allows installers to use a socket wrench or impact gun to apply massive torque, ensuring the screw is driven flush with the wood surface.

• Load Distribution: When used with a large flat washer (DIN 9021) or square washer, the head pulls the two timber members together tightly, creating a rigid friction joint.

2. The Gimlet Point (Sharp Tip)

Our DIN 571 screws are engineered with a sharp “Gimlet Point”.

• Function: This sharp tip pierces the wood fibers immediately upon rotation, allowing for a quick start.

• Installation Note: While the point helps, for diameters larger than 8mm (M8), we always recommend drilling a pilot hole (typically 70% of the shank diameter) to prevent the wood from splitting under pressure.

3. Deep Coarse Threads

The thread profile is designed specifically for fibrous materials. The deep flanks of the thread cut into the timber fibers rather than crushing them, providing exceptional Pull-Out Resistance. This is critical for applications like hanging heavy gates or securing ledger boards for decks.

Material & Corrosion Protection

We offer three tiers of material specification to match your project’s environmental exposure:

1. Indoor Grade (Zinc Plated):

   • Material: Carbon Steel (C1008 / Q235).

   • Finish: Blue/White Zinc Plated (CR3+).

   • Use: Internal furniture, roof truss assembly inside dry attics.

2. Outdoor Grade (Hot Dipped Galvanized):

   • Material: Carbon Steel.

   • Finish: HDG (40-50 microns thick).

   • Use: Garden landscaping, railway sleepers, fencing, and coastal construction. The thick zinc layer heals itself if scratched.

3. Marine Grade (Stainless Steel):

   • Material: SS304 (A2) or SS316 (A4).

   • Use: Boat building, docks, and high-end architectural timber projects where no rust stains are tolerated.

Technical Specifications

Property	Specification Details
Product Name	Hex Head Wood Screw, Coach Screw, Lag Bolt
Russian Name	Шуруп глухарь (DIN 571)
Material	Low Carbon Steel (Q235), Stainless Steel
Diameter	6mm, 8mm, 10mm, 12mm, 16mm (M6 – M16)
Length	30mm up to 300mm (Standard sizes: 8×80, 10×100)
Head Type	Hexagon Head (Hex Flange also available)
Thread Type	Coarse Wood Thread (Partial Thread approx. 60%)
Finish	Zinc Plated (ZP), Yellow Zinc (YZP), HDG
Standard	DIN 571, UNI 704, GOST 11473

Application Scenarios

• Timber Framing: Joining post-to-beam connections in gazebos and pergolas.

• Railways: Securing rail chairs to wooden sleepers (Railway Spikes/Screws).

• Plumbing: Used with a plastic dowel (plug) to fix toilets or heavy pipe brackets to concrete floors (known as “Sanitary Fixing”).

• Decking: Attaching ledger boards to the main house structure.

Quality Control (The “Bending Test”)

A common issue with cheap lag screws is “head snapping” during installation. At HDBolt, we perform a ductility test. We bend the screw shank by 45 degrees; a high-quality screw should bend without snapping. This ensures that even if the wood moves or expands, our screw will hold rather than shear off.

Get a Quote for Bulk Supply

We export 500 tons of DIN 571 screws annually, mainly to Russia and Germany.

Whether you need small boxes (100 pcs) for retail or bulk gunny bags (25kg) for construction sites, please Contact Us for a factory-direct price list.