IMSCREWS 5/16"-18 x 4" Heavy-Duty 304 Stainless Steel Carriage Bolts (10 PCS)

Substantial Reach for 4x4 Post and Structural Timber Connections
The IMSCREWS 5/16" x 4" carriage bolt is engineered for structural projects requiring reliable penetration through thick materials. With a robust 5/16-inch diameter and an extended 4-inch length, these bolts are the ideal choice for securing standard 4x4 timber posts (actual 3.5"). They provide the necessary length to fully cross the post while leaving sufficient thread to accommodate heavy-duty washers and nuts for a snug, permanent connection. Built for durability, they offer the structural stability required for outdoor pergolas, deck framing, and heavy timber construction.

High Durability and Safety-Focused Design
Forged from premium 18-8 (304) stainless steel, these fasteners are highly resistant to rust and corrosion in coastal or humid environments. The smooth round head offers a clean, low-profile appearance that reduces snagging hazards, making them a safe choice for high-traffic residential areas and play equipment. The integrated square neck prevents the bolt from spinning during installation, allowing for easy, one-sided fastening with a single wrench from the nut side.

Specifications:
- Thread Size: 5/16"-18 Coarse (UNC); Length: 4" (Measured from Under Head)
- Material: 304 (18-8) Stainless Steel; Full Thread

Pro-Tips:
1. Use a 5/16" drill bit to ensure a snug, structural fit for the square neck.
2. Pair with stainless steel flat washers and hex nuts on the nut side to distribute load and protect wood fibers.

Key Features

• Extended 4-Inch Reach: Specifically engineered to fully penetrate standard 4x4 posts (3.5 actual thickness) or join thick multi-layer beams with space for washers and nuts.
• Heavy-Duty 5/16 Diameter: The robust 5/16-inch shank offers superior shear resistance and load-bearing capacity compared to 1/4 bolts, essential for structural outdoor joints.
• Premium 304 Stainless Steel: Forged from 18-8 (304) stainless steel for maximum rust protection in coastal air, humid gardens, and corrosive pressure-treated wood (ACQ).
• Safety Round Head Design: The smooth, drive-free domed head eliminates sharp protrusions, providing a snag-free finish that is safe for play sets, benches, and deck railings.
• Anti-Rotation Square Neck: The precision square shoulder locks firmly into wood fibers during installation, allowing for easy, one-sided tightening from the nut side.

Specifications

• ASIN: B0F2F68ZBG
• Internal SKU: IMS0818
• Size: 5/16"-18 x 4"
• Material: Stainless Steel
• Finish: Stainless Steel
• Head Style: Round
• Package Quantity: 10