Let's get right down to the basics. The most important group, of items, that hold your whole scooter together is fasteners. Nuts and bolts can be very confusing to the novice. The concept of assembling components held together with socket-head, button-heads, Torx-head, setscrews, elastic lock nuts (Nylocks), flex-nuts, 12 points and cap screws could become a mind-boggling choice. Add to these decisions the variations of sizes, SAE, metric, grades, finishes and materials and the task to choose the proper fastener can become daunting. I'll try to cut through the minutiae here so you won't be forced into a 4-year engineering degree to understand what type fasteners are appropriate for your motorcycle.

When it comes to hardware, size does matter. Whether you are building a bike from scratch or just replacing some cadmium plated, dull-looking bolts on your Harley for polished chrome ones, You should understand how bolts are sized, along with the proper terms for the different applications and styles.

Here in the USA we use standard types of fasteners, wrenches and tools to install these fasteners. The Society of Automotive Engineers, SAE for short, developed these standards early in the last century, so we Americans who use fractions of inches, instead of tenths-of-meters, would all have a common structure to base our hardware sizes.

This shot shows bolts with coarse and fine threads from left to right.

One of the most common fasteners on your Harley is a 1/4x20 socket cap screw. Now be truthful. Can you go out to your bike right now and point out just one 1/4x20 cap screw? Don't feel bad. There's a large cross section of guys who can't point one out either, and some work on bikes everyday. To understand bolt sizes you'll need is a basic understanding of fractions and inches. Experience, working with sockets, wrenches and fasteners helps a lot.

Bolts are described by the diameter of the shaft, or shank, and the number of threads per inch. So a 1/4x20 socket head cap screw or commonly referred to as an Allen bolt, is 1/4 of an inch in diameter and has 20 threads per inch. All you need is the length of the fastener or how deep it goes into the material for the final dimension, i.e. 1/4x20x1-inch is one inch long. If a bolt is too short for your application, you won't have enough thread engagement to properly hold your bike together. Sometimes, if a bolt is too long, it will "bottom out" and not become tight. It may also interfere with other components.

The number of threads-per-inch determines the difference between "Fine" and "Coarse" threads. Both have advantages when chosen properly. On your American bike there are typical uses for coarse vs. fine threaded fasteners. There are exceptions to these rules, just like in the English language, but in general, coarse threaded bolts are used to fasten a solid piece, billet or casting. Fine threaded bolts are coupled with nuts on the backside of the pieces. The coarse threaded fastener has more "meat" between the threads to grip better in cast materials while the fine thread has more surface area so you can maintain a higher torque value (tightness) on a forged or hardened nut.

Let's shift back to our 1/4x20 example. That's a coarse thread fastener. If you wanted a fine threaded fastener that is a 1/4-in. diameter you would ask for a 1/4x28. Which means it has 8 more threads per inch than the coarse threaded 1/4x20. This holds true for all basic sizes of SAE fasteners. For example 5/16x18 is coarse threaded while 5/16x24 is fine threaded, 3/8x16 is coarse while 3/8x24 is fine threaded and so on. Got it now?

Running from left to right again, the first bolt is a flathead cap screw. The second a socket cap screw. The third is as buttonhead cap screw, and finally, the last, a hex cap screw.

Bolts are also graded, designating how "hard" they are. Maybe you've heard of a "Grade 8" fasteners and wondered what that was all about. Well, wonder no more. Everything has trade-offs and bolts are no exception. The "harder" bolt you choose, the higher the grade number, and the more brittle or "less shear resistant" it becomes. Just because you are using a higher grade, or harder bolt, it might not be the appropriate fastener.

Think of bolts as plastic. If you have a softer plastic rod, it will flex, stretch and bend. If you have a brittle or hard plastic rod, you can pull on it and it won't stretch or break, but if you put side tension on the hard rod, it will snap with very little effort. These two characteristics are important to remember when choosing a bolt. The standard scale of bolt hardness ranges from Grade-2 (soft) to Grade-12 (hard), but a grade 8 is about as hard as you'll find on a Harley. Make sure you are using the same grade washer as the fastener. If you use a lower grade washer (softer) it will "give" or deform in time resulting in a loose bolt.

On a standard "Hex-Cap" or bolt with 6 sides on top, kind of shaped like a stop sign (only different), you'll see markings on the head, cap, or top of the fastener. They indicate what grade the bolt is. Most of the bolts you will be using on your motorcycle will be either a grade 5, which will have 3 slash marks on the top, or a grade 8 which will have 5 slash marks cast into the top. Don't ask me why the SAE decided to mark them this way (probably just to confuse the uninformed).

Other types of fasteners are not marked clearly, so it is important to purchase your fasteners from a reputable dealer. Cheaper fasteners are not hardened the same, or might not have the quality to stake your life on. Can you say "imported"? Beware. The process used to add "tensile strength" or to "harden" fasteners adds to the cost. The harder the bolt the more expensive it becomes. Most of the inexpensive standard hardware at the "Home Improvement" stores are unmarked are grade 2, which are very soft and flexible. They are fine for holding lumber together, but not what you want on your daily ride.

The head or cap of a fastener also determines its style. Different head styles are chosen for ease of installation, accessibility and the ability to take torque or tightness. The most common fastener is a "Hex-Cap" screw. These are the six-sided standard looking bolts that you use a box wrench to tighten. Twelve-Point screws are very similar to a hex cap except they have twice as many points and you'll need a 12-point sockets or box wrenches to tighten them. 12- points are commonly used to attach your lifter-blocks and head bolts on a Big-Twin engine, because generally you can apply a higher torque value to a 12-point fastener.

Socket Cap Screws or Allen head bolts are used all over American bikes. They have a cylindrical rod shaped head with a recessed hex in the top (which has six sides) You insert an Allen style wrench in it for operation.

Torx head bolts are found on many new Harleys and have a rounded cap with a modified star shaped recessed in the cap for a tool similar to an Allen wrench but with more surface area to allow for more torque without stripping the head. A Torx bolt is nearly the opposite of a 12-point cap screw. Torx bolts are also used for quicker assembly in manufacturing situations. They are easy to grasp and more stable on the end of the tool installing them, which makes for a faster installation. They are also well suited for pneumatic (air) tool installation.

Button-Head bolts have a rounded cap top, which also has a hex Allen style socket or a Torx drive socket. Button-Heads are very cosmetically appealing especially when chromed, but do not take well to higher torque values without stripping out.

Finally, a Flat-Head bolt has a cone under the head, which recesses flat into the surface that it mates to. Flat heads are also commonly called counter-sunk Allens. Flatheads also use an Allen (trade name) wrench to tighten them. NOTE: The Allen in the description of the fastener is describing the tool used to tighten the bolt, not the style of fastener. There are tons of different ALLEN bolts, to use the commonly misused term. So it's important to understand the difference and the vernacular to select the proper fastener.

Now for the tough ones, because it means new tools. One the left is the Torx cap screw and right, the 12-point cap screw.

Now, the shiny part. Everybody likes chromed bolts. The guys at the factory in Milwaukee would rather save a couple of cents per fastener, the time it takes for plating and the problems in dealing with plated fasteners and use cadmium or galvanized bolts just to prevent rust. High quality chrome fasteners are available to replace your dull looking ones on your factory machine. One of the top quality US suppliers of chromed and polished hardware is Gardner-Wescott, . They have been in the business of making chromed fasteners for your Harley or Hot-Rod for decades and have a huge variety of domestic high-quality fasteners for your appropriate customizing needs.

Chrome is a durable finish until it is exposed to excessive moisture or salt. If you live by the ocean or in areas where they salt the roads, you may want to consider stainless steel fasteners that are polished. Or you might just want to move somewhere more conducive to custom bikes. The choice is yours. Polished stainless-steel fasteners are almost (the key word "almost") as attractive as their chromed steel counterparts. Stainless steel is generally a stronger fastener and will not show rust but will dull as time and oxidation takes their toll. The process is much slower than a chromed bolt in a damp salty environment.

Chromed bolts will perform and look great here in the dry Southwest, which is also a great place to live. If you take your standard cadmium plated fasteners to your local bumper shop to get them chrome plated, it usually costs more than just replacing them with new production-chromed fasteners. If the plating process is not handled correctly, it may change the hardness characteristic of your fasteners. In addition poor plating will hinder tool fitment, or might chip off the fastener during use. The final point that also bears consideration, when using chromed or stainless-steel fasteners, is the appropriate use of Anti-Seize to avoid galling and binding of the bolts when tightening (see Permatex Loctite tech) which may result in the use of foul language and tool throwing.

If you are still a little confused and want to replace some of your hardware on your bike with chrome fasteners, pull the suckers and take them to a reputable shop such as Surgical-Steeds (more shameless self promotion). By bringing in your old hardware, as an example piece, you'll take the guesswork out of getting the correct fastener and size. If you're planning on building a bike from scratch, hopefully I've helped you make informed decision on what type of bolts to choose for your project. Regardless, it's very important to choose the right fastener and have it installed properly to insure a safe, good looking ride for the long haul.

Gardner-Wescott sells a variety of fastener sets as well as sets for engines, drivelines and wheels. If you can get the right group for your project, it takes the constant trips to the store out of the equation.

Remember, keep the rubber side down.
John at Steeds
www.surgicalsteeds.com

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