Fasten Bolt 7 Letters
Fasten Bolt 7 Letters – Bolts, Nuts and Washers – They hold your ride together. But how well are they doing their job? Fortunately, you read Part 1, which covered engine and driveline fasteners primarily subjected to tension loads—forces exerted primarily along the longitudinal axis of a fastener. With the help of the good guys at ARP Bolts, we explain why specialty bolts are important and how proper metallurgy, heat treatment and fitting procedures are critical to the survival of tension fasteners. We also explain why common commercial hardware doesn’t cut it when used in critical voltage applications. Most of us need specialized hardware as it applies to the parts that produce and sustain the power of a transmission, which is the forte of most of ARP’s bulletproof bolts and studs. But what about the suspension and chassis of a hot rod or race car? That’s where aircraft fasteners have a role to play because things that fly in the sky (no need to pull over your shoulder at 20,000 feet) also make excellent chassis and suspension bolts for a high-performance ground vehicle.
Like many of the loads imposed on an airframe, suspension bolts and nuts are primarily subject to bending or lateral forces. Engineers call these bending forces, exerted perpendicular to the axis of a bolt, “shear loads.” Examples of land vehicles include most suspension bolts and nuts, but also fasteners used to hold pulleys, balancers, flywheels, timing gears, road wheels, sway bar ends, tie rod ends, and similar In this article, we’ll give you a basic overview of shear applications, as well as cover the proper application and selection of high-quality aircraft fasteners that are well-suited to many automotive shear applications. In this regard, we will also discuss some available troubleshooters in ARP screws.
Fasten Bolt 7 Letters
Need to prevent suspension parts from falling off? Use the bolts, nuts and shear washers that have held trusses together for over 70 years.
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“The single shear mount is a crime against nature and a perversion of bad engineering.” -Carroll Smith
If a bolt loaded in shear is supported on only one side of the load, it is said to be installed in “single shear.” If the bolt is supported on both sides of the load, it is in “double shear” and the installation is significantly stronger than an equivalent single shear support because it distributes the loads over a larger area while better resisting bending loads. All induced strains and loads are now in the same plane, minimizing torsion. The rod ends of the four-link suspensions, Panhard bars, Watt link, steering knuckles, control arms, and engine mount through-bolts should ideally be double-sheared. In fact, if designed from scratch, virtually any part of the suspension should be supported in double shear.
Most suspension bolts and rotating parts are subjected to bending or “shear” loads. If a bolt subjected to bending forces is supported on both sides, it is said to be in “double shear”. A properly designed double shear mounting tab and fastener is 70 percent stronger than a single shear joint for the same application.
Unlike a tension application, the most stressed part of a shear-loaded fastener is its shank, so it must fit as tightly as possible into the hole, just before an interference fit. The threaded portion of a shear bolt should never be loaded in shear; This not only decreases the cross-sectional area of the loaded part of the bolt, but also allows the threads to act as a low-speed saw and slowly “egg” the hole, thereby decreasing the integrity of the joint.
Diameter X 2 1/2” Barrel Length, Stainless Steel Brushed Finish. Easy Fasten Standoff (for Inside Use Only) [required Material Hole Size: 7/16”]
Shear bolts should also be designed to bend rather than fracture under overload. This means that ultimate tensile strength is less important for a shearing application than ductility, the ability to roll with punches. If a suspension bolt bends, at least you get home in one piece, where the bolt can be replaced. For bolts made of the same material, those heat-treated to a higher tensile strength tend to be better in tension, but because they are more brittle, they will generally be less desirable in shear.
A “shear bolt” is therefore a very different animal from a “tension” bolt. As discussed in Part 1, the most critical application tension screws have tapered shanks, which distribute longitudinal loads equally throughout the screw while reducing the chance of failure if the shank-to-first thread interface ends up tangential to the surfaces of the material they are joining (which is never good practice regardless). Most tension bolts are used in blind applications (internal threads), and in the automotive world, they tend to have coarse threads because they are installed in relatively low-strength iron or aluminum. Similarly, threads tend to be long, usually 1-1/2 to twice the nominal diameter of the screw.
Airframe fasteners in use on Ron Rollings’ 1957 Chevrolet rear suspension: Note the weight-saving mid-height Nylok on the double shear mount for these CalTracs bars. An AN bolt holds the shock down, but (like many shock mounts) it’s still only in one shear. We would add full height Nyloks to retain the spring U-bolts.
High tech engine tension bolts are great for engines. But not in shear. And forget about those generic commercial grade screws that don’t have full diameter, close tolerance shanks or short threads; they are generally made of low carbon steel and excessively heat treated; and have uncertain quality control. For generic critical shear applications, we need to look to the aerospace industry, which has developed a series of critical “air-cell” bolts to hold things together. Almost all aircraft fasteners are fine wire, which is more resistant to vibration and has a slightly higher load capacity compared to coarse wire of equivalent size. Aircraft fastener threads are Class 3, a tighter and more precise fit than loose, commercial Class 2 threads. Except for the original AN series of bolts, most current production aircraft fasteners also have the profile of J-shaped thread with a larger root radius and a modified crest to minimize stress concentration.
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Do not use commercial grade 5 or 8 bolts (silver in this photo) in critical shear applications. Compare your long poorly machined class 2 threads with the close tolerance shank and short class 3 threads on the gold plane AN and NAS fasteners. The long, full-diameter shanks fit snugly into the hole; Short threads ensure that no threads extend into the hole.
Manufactured under carefully controlled conditions and rigidly inspected, most fuselage bolts have long shanks and short, thin threads, long enough for an airplane washer, a nut, and at least two threads protruding through the nut. Stems have a tight fit within the bore, typically within 0.005 inch or even less of the nominal bore diameter. You may have to tap them into the hole using a punch and a mallet.
Because the threads are short, they come (depending on the specific series) in “grip increments” of 1/8 or even 1/16 of an inch, which is the full length of the stem from under the head to the start of the first thread cable. -in. In other words, you get an airplane screw by the grip length required, not by its overall length. (The only exception is some NAS flat head countersunk screws, where the grip length is measured from the top of the head to the start of the first thread entry, because the head is flush with the material being joined).
The total length of the aircraft screw “takes care of itself”. To the basic grip length, the overall bolt length adds a standard amount of threads for the series and bolt diameter to accommodate a lock nut (or a particular series of lock nuts on some NAS fasteners) and the bottom nut washer, plus of several additional threads. to ensure that the nut and its locking element are fully engaged.
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The length of the bolt grip is equal to the thickness of the material to be joined plus (if used) any washers under the bolt head. Transition of the complete cylindrical part of the rod to the first thread of the bolt with the bottom washer of the nut. The design basis for that transition is usually 0.063 inches (the standard AN washer thickness up to very large bolt diameters). If the material thickness is “between” the available grip lengths, use the next longest grip length and add an additional under-nut washer to make up the difference.
The old basic aircraft screw is the AN (Air Force-Navy) series, which has been around (and constantly refined) since World War II. Relatively inexpensive, they are “only” 125,000 psi tensile strength, but have great ductility and are perfect for most general shear applications. If your AN screws are bent, switch to several 160,000 psi NAS (National Aerospace Standard) hex head screws or MS (Military Standard) taper key and internal key screws. At the top end are several 180,000 psi MS or NAS bolts, 12-point or splined drive. Most of these series are optionally available with drilled heads for the safety thread, drilled shanks for a key, both shank and head drilled, or completely undrilled.
There are aerospace bolts available after 300,000 psi, but anything over 180,000-220,000 psi is not available affordably in the real world, and it’s questionable if they have a place on any land vehicle besides maybe Indy or Formula 1. These exotics are made of special “unobtanium” alloys, so they maintain ductility, even at higher strength levels.
Identify screws by the markings or part number stamped on the head.