How To UseBy Don Casey
The Right Fastener
Published: August/September 2013
First, assess the load this fastener will need to handle. Then choose among very different fasteners for different challenges. Don't worry, Don's here to help you figure it out.
Anything you want to attach to your boat has to be fastened in some way. Today we have astounding glues that are stronger than the materials they bond, and some tapes are capable of joining railroad cars. Most of the time, though, mechanical fastening will be the attachment method of choice. Metal fasteners set the bar for strength, offer unmatched longevity, and most can be disassembled without destruction. Select wisely and install carefully to ensure your fasteners hold to their maximum strength.
Selecting the right fastener (see below) begins by assessing the load that will be placed on it. Any metal fastener will hold well against a sideways (shear) force. But with a tensile force pulling the fastener straight out, holding strength becomes increasingly dependent on the threads (or formed head in the case of rivets) holding the fastener in place. The load on lifting and towing eyes is almost entirely tensile — it is trying to stretch the fasteners or pull them from their holes. When the tide goes out, docklines start to tug upward on cleat fasteners. Pedestal seat bases pry up mightily on their forward fasteners, then on their aft ones as your body weight shifts in a chop.
When Choosing A Metal Fastener, The First Question Is What Type. Here Are Some Options:
- Bolts require nuts and access to both sides of the fastener hole.
- Machine screws are identical to bolts but thread into a tapped hole. Sheet-metal and wood screws are self-tapping, cutting threads into the smooth surface of a drilled hole.
- Rivets have no threads. They come with a factory head on one end, with the other end deformed at installation to create a second "head." The rivets contemporary boat owners are likely to use will be blind rivets, commonly called pop rivets, which can be installed even if you only have access to one side of the fastener hole.
Illustration: ©2013 Mirto Art Studio, www.mirtoart.com
Click on illustration to enlarge
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Buying Quality Fasteners
For marine applications, the fastener material of choice, excluding aluminum rivets, will nearly always be stainless steel. Bronze is equally good but only for fastening bronze hardware. Avoid entirely typical hardware store offerings of brass and plated steel.
Where do you get high-quality marine fasteners? Your local boat-supply store should carry a good selection. Many hardware stores also stock stainless fasteners. However, not all stainless steel is created equal. Try to get a look at the box the specific fasteners came in. Retail fasteners labeled "18-8" are nearly always type 304. You will be better off, particularly if your boating waters are salt, using the more corrosion-resistant type 316.
Finding and obtaining 316 fasteners has become infinitely easier with the Internet and fast shipping. Check Jamestown Distributors, a notable source of virtually every type of fastener that any boat owner (or builder) might need. Unfortunately, you may have to buy 100 when you only need four, so also look for a local source, such as West Marine, and check if they have quality type 304 and 316 screws and bolts. Each fastener will cost more, but you'll spend less overall if you don't need the quantity.