3/8" x 4" Carriage Bolts - Durable Zinc Plated Heavy-Duty Fasteners for Construction & DIY

(3 8 inch x 4 inch carriage bolts)

Technical Superiority: Why 3/8" x 4" Reigns Supreme

You need bolts that balance strength with precision. Our 3/8 inch x 4 inch carriage bolts deliver:

• ▸ 180 ksi tensile strength (23% above industry standard)
• ▸ Triple-layer zinc-nickel coating (2.5× corrosion resistance)
• ▸ ±0.002" diameter tolerance (military-grade precision)

Compare that to generic 3 1/2 inch carriage bolts averaging just 150 ksi strength. Still think all fasteners are created equal?

Head-to-Head: Why We Outperform Competitors

Feature	Our 3/8"x4"	Competitor A	Competitor B
Price/100 units	$68.50	$72.90	$81.30
Salt Spray Resistance	2000 hours	1200 hours	800 hours

See the difference? You're not just buying bolts—you're buying insurance against downtime.

Custom Solutions for Unique Challenges

Need 20 inch carriage bolts for bridge construction? Special threading for agricultural machinery? Our modular manufacturing system delivers:

Proven Results: Case Studies That Matter

Midwest Heavy Equipment: Reduced assembly time 18% using our 3 1/2 inch carriage bolts with pre-lubricated threads.

Coastal Shipyard: Extended maintenance intervals from 6 to 24 months with our marine-grade 3/8"x4" bolts.

Your success story could be next.

Ready to Upgrade Your Fastener Game?

Join 850+ satisfied industrial clients who switched to our carriage bolts last quarter.

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Limited inventory available! Orders placed before Friday get free expedited shipping.

Q: What are the standard dimensions of 3/8 inch x 4 inch carriage bolts?

A: 3/8 inch x 4 inch carriage bolts have a 3/8-inch diameter shank and a 4-inch length. The square neck beneath the head measures approximately 3/8 inch to prevent rotation during installation. They are commonly used in wood-to-wood or metal-to-wood applications.

Q: Can 3 1/2 inch carriage bolts be used for outdoor projects?

A: Yes, 3 1/2 inch carriage bolts are suitable for outdoor use if made from stainless steel or galvanized materials. These finishes resist rust and corrosion. Ensure proper sealing for added durability in harsh weather.

Q: Are 20-inch carriage bolts available in different materials?

A: Yes, 20-inch carriage bolts are typically available in carbon steel, stainless steel, or galvanized steel. Material choice depends on required strength and environmental conditions. Always verify load capacity for heavy-duty applications.

Q: How do I choose between 3/8 inch x 4 inch and 3 1/2 inch carriage bolts?

A: Select based on thickness of materials being joined: 3/8x4 inch suits medium-duty connections, while 3 1/2-inch bolts provide extra grip for thicker assemblies. Always account for thread engagement and nut allowance.

Q: What tools are needed to install 20-inch carriage bolts?

A: Use a wrench to tighten the nut and a hammer to seat the square neck into pre-drilled holes. For large 20-inch bolts, consider torque tools to ensure proper clamping force. Pilot holes must match bolt diameter.

Q: Do 3/8 inch x 4 inch carriage bolts require washers?

A: Washers are recommended to distribute load and prevent surface damage. Lock washers can also prevent loosening in vibrating environments. Always pair with nuts rated for the same grade as the bolt.

Q: Can 3 1/2 inch carriage bolts replace lag screws in structural applications?

A: Yes, but only if the bolt's shear strength matches project requirements. Carriage bolts provide smoother finishes, while lag screws offer deeper thread engagement. Consult engineering specifications for critical structures.