How to Choose the Right Carriage Bolt for Your Project
Choosing the right carriage bolt isn’t just about picking a random size. The correct selection depends on where you’re using it, what it’s connecting to, and how long you want it to last.
As a professional carriage bolt manufacturer, Xinchi is glad to share some practical tips based on real-world use cases to help you make the right choice.
Carriage Bolt Material: Carbon Steel vs Stainless Steel
The first thing to consider is where the carriage bolt will be used.
- Carbon steel carriage bolts are strong and economical, great for indoor use or dry environments like furniture, crates, or wooden framing.
- Stainless steel carriage bolts (304 or 316) are better for outdoor or high-humidity areas like decks, fencing, docks, or coastal construction.
For general outdoor projects, 304 stainless is usually enough. For marine or chemical environments, 316 stainless is a safer long-term option.
Carriage Bolt Size: Choosing the Right Diameter and Length
Getting the right carriage bolt size ensures proper fit and holding strength.
Common diameters: M6, M8, M10 — M6 and M8 are typical for wooden structures, while M10 and above are used for heavier loads.
Length tips: Measure the thickness of all materials being fastened, then add at least 15mm to allow for washers and a nut.
Example: For a 30mm wood plank, a 45–60mm bolt is generally safe, depending on whether you use flat washers.
Carriage Bolt Finish: Zinc-Plated vs Hot-Dip Galvanized
The finish or coating of your carriage bolt affects corrosion resistance, especially in outdoor environments.
Zinc-plated carriage bolts: Bright appearance, light-duty rust protection, good for indoor projects.
Hot-dip galvanized carriage bolts: Thick, rougher coating, excellent for outdoor use like decks and fences.
Plain finish bolts: For dry indoor use only—no corrosion protection.
Pro tip: If you’re working outdoors, skip zinc plating and go with hot-dip galvanized or stainless steel carriage bolts.
Carriage Bolt Accessories: Nuts and Washers Matter
Every carriage bolt setup requires the right accessories to function properly.
Nuts: Use standard hex nuts or nyloc nuts for extra vibration resistance.
Flat washers: Spread the load, protect the surface, especially on soft wood.
Spring lock washers: Add grip and help prevent loosening under vibration.
Important: Match the finish—use hot-dip galvanized nuts with hot-dip galvanized bolts, or they may not fit properly and could corrode faster.
Final Tips on Choosing Carriage Bolts
To sum it up, here’s what to keep in mind when choosing the right carriage bolt:
- Use carbon steel for indoor projects, stainless steel or galvanized for outdoor or damp environments.
- Measure carefully to choose the right bolt length and diameter.
- Choose the right coating or finish based on where the bolt will be used.
- Don’t forget proper nuts and washers to complete the installation.
Looking for a Reliable Carriage Bolt Supplier?
At Xinchi Fasteners, we manufacture and export a full range of carriage bolts, including:
- M6–M12 sizes, customized lengths available
- Carbon steel, 304, and 316 stainless steel options
- Zinc plating, hot-dip galvanizing, black oxide coating
- High daily output: over 10 million pieces, 102 cold heading machines
- Fast lead times and strict quality control for global orders
XINCHI is a trustworthy fastener company, especially in furniture nuts. We have a factory, founded in 2007. We are the designated fastener supplier to“STAPLE”. As a trusted fastener supplier, XINCHI offers a wide range of high-quality fasteners, including nuts, screws, bolts, rivets, and washers.
Feel free to reach out to get a quote or discuss your project specs.