Product Classification: Eye Lag Screw
An eye lag screw (also known as a screw eye or eye lag bolt) combines a formed loop head with a wood-threaded shank, creating a permanent anchoring point for cables, ropes, chains, or hanging hardware. Unlike standard machine thread fasteners, the wood thread profile is designed to cut into and compress wood fibers, providing superior pull-out resistance without requiring a nut or pre-threaded hole.
The illustrated M12 × 135 mm configuration represents a common specification where:
M12 refers to the nominal thread diameter (approximately 12 mm)
135 mm indicates overall length from under the eye to shank end
The eye head accommodates hook, rope, or cable attachment
Wood Thread Profiles: Selecting the Right Geometry
Different wood substrates require different thread geometries to achieve optimal holding strength. We offer multiple wood thread profiles, each engineered for specific applications:
| Thread Profile | Characteristics | Suitable Substrates |
|---|---|---|
| Coarse Wood Thread | Deep, widely spaced threads; aggressive bite | Softwoods (pine, fir, cedar), low-density composites |
| Fine Wood Thread | Shallower, closely spaced threads; reduced splitting risk | Hardwoods (oak, maple, walnut), dense engineered wood |
| Dual-Lead Thread | Two parallel thread starts; faster installation | Production assembly, softwoods, medium-density fiberboard |
| High-Low Thread | Alternating high and low thread crests; superior pull-out resistance | Particle board, MDF, recycled wood composites |
| Tapered Thread | Progressive thread depth from tip to shank; self-centering | All wood types, general purpose |
Wire Diameter & Strength Considerations
For non-standard wood screws, wire diameter (the raw material diameter before thread rolling) directly influences both thread geometry and ultimate strength. Larger wire diameters produce deeper, more robust threads but require greater driving torque; smaller diameters offer easier installation with reduced holding capacity.
| Wire Diameter | Thread Characteristics | Typical Applications |
|---|---|---|
| Smaller Gauge | Shallow threads, reduced driving torque | Softwoods, decorative applications, light loads |
| Standard Gauge | Balanced thread depth and strength | General construction, furniture, medium loads |
| Larger Gauge | Deep, aggressive threads, maximum holding | Structural wood, heavy loads, outdoor applications |
Eye Head Configurations
| Eye Type | Description | Applications |
|---|---|---|
| Round Eye (Closed) | Fully closed loop; welded or forged construction | Lifting, permanent attachment, safety-critical |
| Open Eye (Hook Style) | Partially open loop for quick attachment | Temporary connections, adjustable rigging |
| Offset Eye | Eye angled relative to shank | Clearance or alignment requirements |
| Welded Eye | Separate eye ring welded to shank | Heavy loads, high-strength requirements |
Material Options
| Material | Properties | Applications |
|---|---|---|
| Carbon Steel (Grade 4.8 / 8.8) | High strength, cost-effective | General construction, furniture, industrial |
| Stainless Steel (304 / 316) | Corrosion resistance, aesthetic finish | Marine, outdoor, food processing, coastal |
| Zinc-Plated Carbon Steel | Moderate corrosion protection | Indoor applications, light outdoor exposure |
| Hot Dip Galvanized | Heavy-duty corrosion protection | Exterior structural, marine, agricultural |
Surface Finishes
| Finish | Corrosion Resistance | Appearance | Applications |
|---|---|---|---|
| Zinc Plating (Clear/Yellow) | 72–120 hrs salt spray | Bright, decorative | General indoor, hardware |
| Zinc-Nickel | 500–1,000 hrs salt spray | Matte silver | Automotive, high corrosion |
| Hot Dip Galvanized | 1,000+ hrs salt spray | Dull gray | Exterior structural, marine |
| Black Oxide | Moderate (with oil) | Black matte | Decorative, light-duty |
| Passivation (Stainless) | 500–1,000 hrs salt spray | Natural metal | Marine, medical, food |
| Parameter | M12 × 135 Example | Custom Range |
|---|---|---|
| Nominal Diameter | 12 mm | M4 – M20, #8 – 3/4″ |
| Overall Length | 135 mm | 50 – 400 mm |
| Thread Type | Coarse wood thread | Custom profile per application |
| Wire Diameter (Pre-Thread) | 9.0 – 10.5 mm | Custom per thread geometry |
| Eye Inner Diameter | 25 – 35 mm | 15 – 60 mm |
| Eye Material | Formed from shank or welded | Integral or welded construction |
| Material | Carbon steel / Stainless | Per customer specification |
| Surface Finish | Zinc-plated / Custom | Various plating and coating options |
| Tensile Strength | 400 – 800 MPa (dependent on grade) | Per material selection |
| Pull-Out Resistance | Substrate dependent | Optimized via thread profile |
Thread Profile Comparison
| Thread Type | Crest Height | Pitch | Driving Torque | Holding Power |
|---|---|---|---|---|
| Coarse Wood | Deep | Wide | High | Maximum |
| Fine Wood | Shallow | Narrow | Low | Moderate-High |
| Dual-Lead | Moderate | Double start | Low | Moderate |
| High-Low | Alternating | Variable | Moderate | High (in composites) |
| Tapered | Progressive | Standard | Low | Moderate |
| Application | Recommended Thread | Material | Finish |
|---|---|---|---|
| Softwood decking | Coarse wood thread | Carbon steel | Hot dip galvanized |
| Hardwood furniture | Fine wood thread | Stainless steel | Passivated |
| Particle board shelving | High-low thread | Carbon steel | Zinc-plated |
| Marine dock hardware | Coarse wood thread | Stainless steel 316 | Passivated |
| Outdoor landscaping | Coarse wood thread | Carbon steel | Hot dip galvanized |
| Light-duty hanging | Fine wood thread | Zinc-plated steel | Zinc-plated |
| Structural wood connection | Coarse / Dual-lead | Carbon steel Grade 8.8 | Zinc-nickel or HDG |
Application Examples by Industry
| Industry | Typical Use | Recommended Spec |
|---|---|---|
| Construction | Anchor points, cable stays | M12–M16, coarse thread, HDG |
| Furniture | Hanging hardware, leg attachments | M6–M10, fine thread, plated |
| Marine | Dock lines, boat lifts | M10–M16, coarse thread, 316 stainless |
| Agriculture | Fencing, tether points | M10–M20, coarse thread, HDG |
| Playground Equipment | Swing hangers, anchor points | M12–M16, coarse thread, galvanized |
| Retail Display | Hanging fixtures, shelving | M6–M10, fine thread, plated |
| Custom Feature | Options |
|---|---|
| Thread Profile | Coarse, fine, dual-lead, high-low, tapered, custom geometry |
| Wire Diameter | Custom gauges to optimize thread depth for specific substrates |
| Eye Configuration | Round, open, offset, welded, reinforced |
| Eye Orientation | In-line with shank or angled |
| Length | 50 – 400 mm, custom increments |
| Diameter | M4 – M20, #8 – 3/4″ |
| Material | Carbon steel, stainless steel, alloy steel |
| Surface Treatment | Zinc, Zn-Ni, HDG, black oxide, passivation, custom coatings |
| Marking | Size, grade, or custom identifiers |
Dimensional Verification: Thread profile, length, eye geometry confirmed per drawing
Pull-Out Testing: Sample testing on representative substrates
Material Certification: Chemical composition and mechanical properties
Coating Verification: Thickness, adhesion, corrosion resistance
Visual Inspection: 100% for critical dimensions on production orders
Packaging Options
Bulk cartons: 100–2,000 units
Poly bags with labels for retail or hardware packaging
Custom kitting with washers, hooks, or installation hardware
