What makes a Carriage Bolt a Carriage Bolt?
What is a carriage bolt and what is it used for?
Carriage bolts, also known as coach bolts or cup head bolts in Australia and New Zealand, have a round head, a square neck, and are generally partially threaded. They were originally designed for fastening wood to metal, or metal to metal as the square neck area of the bolt was meant to fit in to a square socket in the metal. This portion of the neck serves to hold the bolt stationary as a nut is screwed on or off. These days, we use carriage bolts for all kinds of uses, and when fastening on a boat they are most often used for fastening wood to wood, but could also be used for fastening wood to metal such as in bronze knees.
Why are carriage bolts only partially threaded?
The unthreaded portion of a carriage bolt is there for a reason, I assure you! Structures, and boats in particular, work, flex, twist, and move when they're put to use. Even the strongest, stoutest built vessel is alive with movement when subjected to all of the forces put on it out in the water. This movement is exactly why having a partially threaded bolt is important.
Know what kind of carriage bolt you're buying!
I recently checked out some of my competitors' products and was surprised at how inexpensive some of their carriage bolts are. Having gone through lots of product testing myself I was surprised they could sell a carriage bolt at such a price. Then I ordered some...
It's so easy to purchase low grade fasteners (especially online) but is that what you really want to use? When pouring time, effort, blood, sweat, and tears in to a boat build or restoration it would be disheartening to see it all come undone by fasteners that are not up to the task because they're the wrong alloy or in this case are threaded where they shouldn't be. Trust that at Fair Wind Fasteners we've taken the time to test for quality, and would NEVER sell anything we wouldn't use ourselves.
Have a look at some of the comparison photos below, you'll easily be able to see which Silicon Bronze carriage bolt is ours, and which is theirs. Is it even a carriage bolt if it's fully threaded? I say no.