Durable 5/16 x 3-1/2 Carriage Bolts Heavy-Duty for Woodworking & Construction

(5 16 x 3 1 2 carriage bolt)

The Unbeatable Tech Behind 3.5 Inch Carriage Bolts

What makes our 5/16 x 3 1/2 carriage bolts your best ally? Three revolutionary design features. See the difference?

Forged Grade-5 steel cores resist 120,000 PSI shear force – 40% stronger than standard hardware.

Deep-domed heads lock wood without cracking. Perfect for timber framing and deck posts.

Diamond-knurled necks grip materials permanently. Zero slippage even under vibration stress tests!

Spec	5/16 x 3 1/2"	3/8 x 9"	3" Standard
Shear Strength	120,000 PSI	105,000 PSI	85,000 PSI
Corrosion Shield	Triple-Zinc	Hot-Dip Galv	Basic Zinc
Vibration Cycles	50,000+	35,000	18,000

Why Giants Choose Us Over Generic 3 Carriage Bolt Suppliers

Frustrated by suppliers with inconsistent sizing? Our precision matters down to 0.002-inch tolerance.

Our direct-to-jobsite delivery beats competitors' lead times by 72 hours on average.

Custom packaging prevents damage during transit. Broken bolts? That's history!

Real advantage: Threads cut not rolled. They bite harder and last longer.

Your Project, Your Rules: Custom 3.5 Inch Carriage Bolt Options

Need unusual sizes like 5/16 x 4.5"? Our workshop delivers custom batches in 48 hours.

Specialized finishes:

- Marine-grade stainless for docks
- Black oxide for aesthetics
- Hot-dip galvanized for harsh environments

We laser-etch markings per your specs. Brand them as yours or track inventory codes.

BridgeSafe Inc: How 5/16 x 3 1/2 Bolts Saved a $4M Contract

BridgeSafe faced constant joint failures on Ohio River walkways. Their old bolts? Disintegrating.

Our carriage bolts with triple-zinc coating solved it. Installation speed increased by 65%!

Maintenance costs plummeted. Zero replacements needed in 18 months.

Project engineer said: "We've finally stopped fighting loose connections."

Ready to Eliminate Bolt Failures Forever?

Since 2009, BoltMaster Industries has secured over 7,000 structures globally.

Join 1,200+ contractors who switched to our carriage bolts.

Free engineering consultation with every bulk order!

Request Your Custom Bolt Quote Now

P.S. First-time buyers save 15%! Offer expires July 31.

Q: What are the dimensions of a 5/16" x 3.5" carriage bolt?

A: A 5/16" x 3.5" carriage bolt has a 5/16-inch diameter shank and a 3.5-inch length under the square neck. It is commonly used in wood-to-wood or metal-to-wood applications. The square neck prevents rotation during installation.

Q: Where is a 3/8" x 9" carriage bolt typically used?

A: A 3/8" x 9" carriage bolt is ideal for heavy-duty construction, such as securing large timber or structural components. Its longer length provides ample threading for nuts. Ensure proper load distribution with washers.

Q: What does a "3 carriage bolt" refer to?

A: A "3 carriage bolt" likely refers to a 3-inch-long bolt with a standard diameter (e.g., 1/4" or 5/16"). Confirm the exact diameter and thread specifications before purchase. Commonly used in furniture or light framing.

Q: Are 3.5-inch carriage bolts corrosion-resistant?

A: This depends on the material. Standard 3.5-inch carriage bolts are zinc-plated for mild corrosion resistance. For harsh environments, opt for stainless steel or hot-dipped galvanized variants.

Q: Can a 3/8" x 9" carriage bolt replace a 5/16" x 3.5" one?

A: Only if the hole and load requirements allow for a thicker bolt. The larger diameter and length may affect fit and strength. Always consult engineering specifications before substituting.