Chrome hardware has never been more popular. Demand for shiny specialty nuts, bolts, screws, and washers increases yearly. Attention to detail is always high on the list for custom machines, and chrome fasteners are the finishing touch. Modern enthusiasts pour a lot of blood, sweat, and tears into their motorcycle of choice to make it just right, and that includes knowing the ins and outs of chrome-plated hardware. We all know why chrome is desired in the first place: It's pretty and shiny! A flawless, mirror-like finish is what's so appealing. But a perfect luster must be accompanied by high strength and excellent durability, though in the past this wasn't always a given.
Certain high-profile problems traditionally associated with chrome-plated fasteners-a reputation for hassles in usage, lack of fastener strength, and poor durability-are the downsides. Not uncommon are nightmare stories of fasteners seizing during installation, shearing off at the head, or the chrome cracking and peeling. These problems can be cruelly frustrating, since the hassle of extracting a broken bolt or chasing out stripped threads isn't usually seen as productive time. Most often these issues occur due to poor metal quality or incorrect manufacturing techniques.
For example, unless thickness is very carefully controlled, adding a layer of chrome plating to a fastener increases interference between male and female threads beyond the original design specification. This is the cause of galling (or seizing), which occurs when the metal high points between fastener and casting (or nut and bolt) lock together.
Mysterious breakage of improperly produced chrome-plated fasteners is far too common. The culprit is a little-known but highly controversial condition known as "hydrogen embrittlement." Created by the absorption of atomic hydrogen into the fastener's surface during the chrome-plating process, it reduces the strength and elasticity of fasteners significantly, hence the easy snapping (shearing) of a too-brittle fastener at the head or body. Basically, hydrogen gas is trapped under the chrome. When stress is applied to the fastener during use, or through torque during installation, the hydrogen gas migrates to the points of highest stress concentration within the fastener. Ruptures occur internally, and breakage happens when the lesser strength and increased brittleness of the metal are exceeded. Shearing is sudden, and there are no visible warnings in advance. The scary part is that a fastener can be installed, everything seemingly fine, and later on fail, most often at the worst possible time. Ironically, the stronger-grade fasteners made of high-strength, high-carbon-alloy steel can be the worst offenders. The higher the carbon content in the alloy, the stronger the base metal, and, sadly, the more susceptible it is to hydrogen embrittlement. The key to eliminating hydrogen embrittlement is a post-bake process. The fastener is heated to a specific temperature for a specific period of time to bleed out the hydrogen gas through the chrome plating. So if a chrome-fastener supplier offers Grade 5-quality fasteners or even higher-carbon-content Grade 8, they darn well better be post-baked.
Less drastic, but certainly no less annoying, is cracking and peeling of the chrome. This condition is typically caused by sharp edges on the fastener, which create pressure points that result in small fissures and chips in the chrome plating. When stresses are applied, this microscopic damage to the plating often migrates and magnifies. More often than not, this cracking occurs not when the fastener is installed, but instead when it's time to remove it. Too much of this behavior can lead to a sort of one-time-use mentality regarding chrome nuts and bolts. It doesn't have to be this way. More gentle radiuses and proper stress relief after the plating process occurs are the answer to this hassle.
These aren't the only issues that need to be addressed, either. Some critical fasteners on your Harley-Davidson simply shouldn't be swapped for chrome without serious research into whether a shiny substitute is up to the stresses and tensions required of the factory part. Usually a responsible manufacturer of chrome and/or stainless hardware will not list a replacement in its catalog if there's any potential problem. The rule of thumb should be "if it isn't listed, don't do it." Trouble is, you might not know what is or isn't offered by a manufacturer. In that case, consult at least three professionals, and if the consensus is that it's safe to substitute, go ahead. If not-leave it alone.
Sometimes, the sheer hassle of replacing all the screws for an inspection cover or some similar situation makes using a chrome fastener more trouble than it's worth, especially if you're not mechanically inclined. For those of us in this boat, there are covers and inserts for practically any area of your machine where fasteners are used.
The bottom line is that nowadays any of these evils can be avoided. Adding that shiny finishing touch to your machine doesn't have to be a hassle and won't give you problems later if you're willing to do a little work in advance by carefully sourcing chrome fasteners from a manufacturer that uses high-grade metal and employs the correct manufacturing procedures.