Table of Contents:

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• What Is a Fastener?
• Different Types of Fasteners
  • • Screws
    • Nails
    • Bolts, Nuts and Washers
    • Anchors
    • Rivets
• Different Uses for Fasteners
• Quality Fasteners From the Fastener Experts

Types of Fasteners

Fasteners play a critical role in the construction of all sorts of everyday objects. If you've done any DIY projects, you've likely used fasteners to help get the job done. At All Points Fasteners, we're passionate about the role quality fasteners can play for handy homeowners and professionals alike. Let's take a moment to define fasteners and overview some of the different types, as well as the various uses for them.

What Is a Fastener?

Let's start by defining what a fastener is. The term fasteners encompasses a fairly broad category of tools, such as screws, nuts and bolts, that share a common purpose: to mechanically hold objects together. Of course, things like glue can fulfill this function, but glue is not a type of fastener. Therefore, we need to add to our definition. Hardware fasteners mechanically hold objects together.

Typically, fasteners form a non-permanent joint. In other words, when you use a fastener to connect two components, you can remove it, and the separate pieces should come apart without suffering any damage. The same wouldn't be the case with a welded joint, for instance. The one exception to this rule are rivets, which fall under the category of fasteners, but create permanent joints.

Though most fasteners form a non-permanent joint, this does not mean you only use fasteners when you want to be able to take something apart, and it doesn't mean the joint is weak by any means. Fasteners can reliably hold together objects that can experience a great degree of stress. That means they're a great choice for permanent and non-permanent joints alike, providing versatility for the type of project you want to use them for.

Different Types of Fasteners

Mechanical fasteners come in many forms, including screws, nails, nuts, bolts, washers, anchors and rivets. Each of these different types of fasteners is a category unto itself, with many types to choose from. If you've ever been in a fastener aisle at a hardware store, you know how many different types of fasteners are out there. Let's look at each of these common examples of fasteners and break them down a bit further.

1. Screws

For many people, when they think of fasteners, screws are the first thing to come to mind. Screw fasteners are one of the most versatile types of fasteners out there. Their threaded shafts give them durable holding power, and unlike a bolt, they don't require anything to hold them in place. Typically, you use a drill to make a pilot hole in a material and then use a screwdriver to drive the screw in place. Screws come in a wide variety of types and sizes. Some of the most common types of screws include:

• Wood screws have coarse threads and a tapered head.
• Deck screws are similar to wood screws, but include self-tapping designs and corrosion resistance for outdoor applications.
• Drywall screws feature a self-tapping head that can countersink without causing damage to drywall.
• Sheet metal screws have sharper threads for connecting metal to other materials.
• Machine screws have a uniform thickness and don't taper off at the bottom.
• Masonry  Screws A masonry screw is specially designed to cut into concrete and brick. A drywall screw has twin threads to allow for quick, easy installation.
• Board screw This is designed specifically for wood or wood-type materials such as MDF or fibre board. They are self-tapping in as much as they will tap their own threads and do not need to be used with a pre threaded insert. It has a sharp point for easy starting and holds a grip within the wood so it will not slip.
• Exterior screw This is treated with an anti-rust coating to prevent corrosion or rust and is ideal for decking, joists or fences.

Size:

Be sure to choose a screw that is long enough for the job. If you are joining two materials together, you want to choose something

that is long enough to penetrate and grab both pieces. A screw that is too short may not be able to keep the materials fastened. A screw that is too long, on the other hand, may damage the wood on the other end.

You also want to choose the right diameter for the job as well. A screw that is too large may look unattractive or split softer, more fragile wood. On the other hand, a screw that is too small may not hold the materials well.

Heads:

Screws also have their own types of heads. They can be flat, which will allow you to countersink the screw into the material; rounded heads, which tend to be more decorative; or flanged, which eliminate the need for washers. You also have a choice in what type of drive you use on the screw. The most popular drives for contractors are:

• Hexagonal, which fits in magnetic bits and drive quickly; and
• Square, which doesn't strip as quickly as others.
• Other less common drives include slotted, quadrex and Torx.

For the best results, chose the right screw for your application. If you're not sure what you need, go ahead and give us a call.  We'll be more than happy to help you figure out what self tapping screw will do the job for you.

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2. Nails

Nails have been used since ancient times, and they are still an everyday household item. You can easily spot the difference between a screw and a nail because a nail doesn't have threading. While a nail doesn't provide the same holding power a screw does, it has greater shear strength, making it the better choice for some applications.

Many types of nails take their names from their applications, which can make it a snap to find the right variety of nail for a job. They typically have specific characteristics designed for working with the materials or application at hand.

Some common kinds of nails include the following:

• Common nails have a thicker shank for greater holding power for many different applications, but the thick head will be visible on most projects.
• Box nails offer easier driving with a steel construction and diamond-point tip.
• Brad nails can easily blend into wood trim.
• Finishing nails are for more detailed work and have a small, flat head designed to blend in with project finishes, such as those on crown molding.
• Drywall nails are designed for easy concealment and reduced slippage.
• Flooring nails are designed for use with various flooring materials.
• Framing nails can include a variety of styles, often designed for flush installation and easy concealment.
• Roofing nails have a wide head and are often corrosion-resistant.

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3. Bolts, Nuts and Washers

Nuts and bolts are another common type of fastener. These two pieces work in tandem to hold components together. You insert the bolt through the two parts you want to join, then fasten it in place with a nut on the end. Here are some of the most common types of bolts you'll use:

• Carriage bolts have domed or countersunk heads with a square component under the heat to keep the bolt from moving while tightening the nut.
• Flange bolts include a circular flange beneath the head for distributing loads evenly.
• Plow bolts are for heavy-duty applications, such as heavy equipment, with non-protruding heads.
• Hex-head bolts are six-sided with machine threads.
• Square-head bolts have square heads, offering an easier grip for wrenches.
• Allen bolts have a hexagonal socket for use with Allen wrenches.

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Below are some of the most popular types of nuts and their designs:

• Coupling nuts are hex-shaped and join two male threads together.
• Flange nuts have a wide, serrated flange on one end that serves a similar function as a washer but without any added movement.
• Hex nuts are the most common variety, featuring a hex shape and internal threads.
• Lock nuts include designs to prevent loosening due to vibrations.
• Slotted nuts have sections cut out to create a locking mechanism with the help of a cotter ping.
• Square nuts feature a square shape for greater surface area.
• Wheel nuts are designed for securing wheels onto vehicles.

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Nuts and bolts can function on their own, but sometimes, you'll want to add a washer in between. A washer is a flat disc with an opening in the center. This little piece can distribute the fastener's load more evenly across the surface of the material. Some types of washers are:

• Beveled washers add stability when attaching unparallel surfaces.
• Flat washers are round and thin.
• Lock washers use various mechanisms to prevent nuts, screws and bolts from vibrating loose.
• Structural washers are thicker and used in heavy-duty applications.

4. Anchors

Anchors get their name because they serve a similar function to a boat's anchor, which embeds itself in the seabed to keep a ship from moving. Generally, people use these fasteners to connect something to a material like drywall or concrete. They embed themselves in the material and hold the object you're affixing in place. Some common types of anchors include:

• Internally threaded anchors
• Externally threaded anchors
• Masonry screw and pin anchors
• Screw anchors
• Hollow wall anchors
• Sleeve anchors
• Drive anchors

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5. Rivets

A rivet creates a permanent joint between two objects. They consist of a cylindrical shaft with a head on one end and a tail on the other. You use a unique tool to expand the tail, so the rivet stays in place. Rivets are remarkably durable, compared to other types of fasteners. Some common types of rivets include:

• Blind rivets
• Semi-tubular rivets
• Solid rivets
• Split rivets
• Drive rivets

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Different Uses for Fasteners

What are fasteners used for? That question is somewhat tricky to answer, because fasteners have nearly limitless applications. Homeowners are likely to use fasteners for many DIY projects and basic household tasks. Workers in various industries can use industrial fasteners for all sorts of projects. If you need to attach two components, a fastener is likely the way you'll do so. Here are some examples of common fastener uses.

• Vehicle assembly: You can find small fasteners throughout an automobile, including under the hood, in the suspension system and wherever else there is a connection between two parts or components, such as lock nuts on tires.
• Picture hanging: Small fasteners are prevalent in virtually every area with decorations hanging on the walls. Homeowners and other decorators use them when placing pictures and for other essential purposes.
• Building and construction: A metal fastener can serve multiple purposes to ensure materials stay together during construction projects.
• Furniture assembly: Furniture makers rely on fasteners when assembling their products and preparing them for sale to customers.
• Cabinet installation: Home improvement contractors need an assortment of fasteners when working on kitchen cabinet installation and renovation projects.
• Electronics manufacturing: Fasteners play a prominent role in the production of electronic machinery, components and goods used in the workplace and at home.
• Wall installation: Workers use anchors in tandem with screws to create firm mounts on drywall panels.
• Roofing projects: Roofing nails and framing nails are essential when installing new roofs or conducting repairs and maintenance on existing structures.
• Woodworking: Not all fasteners are for holding two metal objects together. Carpenters and other construction and building professionals use wood screws to form solid connections between parts made of plywood and other wood materials.
• Flooring installation: Companies require flooring nails when installing some types of products in homes, office buildings, factories, warehouses and commercial and retail establishments.

The list could go on and on. Look around your home or business, and you'll see fasteners holding countless objects together.

What Are the Benefits of Using Small Fasteners in Manufacturing?

Screw fasteners are prevalent in numerous industries, including manufacturing. Some advantages of using them in this area include:

• Increased designing flexibility: Fastener screws give designers and engineers more options when creating products. For example, companies that manufacture electronic devices like laptops and tablets can make these items less expensive for consumers by using fasteners instead of welds and adhesives when attaching specific parts and components. Screws also make these items easier to repair.
• Reduced waste: Many products require the assembling of multiple parts and components. Fasteners enable companies to complete the process with fewer materials, which generates less waste and lowers production costs. Manufacturers only need to create small, pre-drilled holes to accommodate screws, nuts and bolts to facilitate the final assembly.
• Lower product weight: Several industries are now turning to lighter, more agile products to reduce manufacturing costs, improve their appearance and make objects easier to handle and use. Small screws are perfect for these items, as they meet the basic fastening requirements and lower the product's weight.

Quality Fasteners From the Fastener Experts

At All Points Fasteners, we carry a diverse inventory of high-quality fasteners, including uncommon fasteners you may not find at your local hardware store. We carry products from leading manufacturers with an excellent reputation for designing and constructing exceptional products that solve problems, reduce costs and stand the test of time. You can count on anything you purchase from us to meet your expectations and add value to your projects.

Reliable Screw Fastener Selection Assistance

Are you having trouble deciding which fasteners are right for your applications or projects? We're here to help. Our experts can give you the advice and guidance you need to find the right fastener for any job. And if we don't have the part you're looking for in our inventory, we can source it for you quickly to minimize downtime.

Our company is American-owned and -operated, so you can expect a quick turnaround on your orders. We always go the extra mile to provide excellent customer service, so you can trust us to help you get the job done.

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You'd expect an engineer to know everything about a basic subject like nuts and bolts right? Well fasteners are one of those topics that seem simple at first but turn out to have much more depth than you expected. What follows are 10 tricks on this 'basic' subject that might surprise you!

UPDATED MARCH : It has come to my attention that there is testing data available that makes the counter argument to my first point in this article. In the interest of transparency and good scientific discussion, I've provided links to all sources mentioned at the end of point #1. When faced with contradictory test results, if we assume the methodology and integrity of all sources are without fault, it is reasonable to conclude that your results may vary. Many factors could significantly affect testing results including variances from manufacturing process, fastener & clamped materials, heat treating, surface finishes, ambient conditions, and bolt diameter.

1. Split washers have been experimentally proven to be ineffective locking devices and can even aid self loosening over time. And yet I see these things in use everywhere, so what gives?

In theory split washers (aka lock washers or helical spring washers) are supposed to work by squishing flat between the nut and the mounting surface when you tighten them. At this point the sharp edges of the washer are supposed to dig into the nut and mounting surface to prevent counter-clockwise rotation.

In practice a split washer is unable to gain any purchase against hard surfaces and does not actually prevent rotation. The problem is that split washers make for poor springs and bottom out after only a small percentage (on order of 10%) of a bolt's total clamping load.

The only time a split washer might prove useful would be for fastening onto soft easily deformed surfaces such as wood, where the washers springiness & sharp edges could actually work.

The evidence against split washers started stacking up in the 's when a gentleman named Gerhard Junker published some of his lab experiments. He invented a machine specifically for testing the effect of vibrations on threaded fasteners. The first thing he discovered was that transverse vibration loads generate a much greater loosening effect than do axial vibrations. Good to know.

If you want to learn more, please visit our website Hebei Bentley Technology.

His second discovery was made by plotting the bolt tension vs vibration cycles to create a 'preload decay chart'. When he compared the preload decay of a bolt & split washer combo to bolt by its lonesome, he found that the split washer caused the connection to loosen sooner, as seen below.*

Not to worry, there are better locking options available. Chemical lockers like Loctite, deformed thread lock nuts, and Nyloc nuts should be your everyday go-to locking devices. If you have some money to burn then wedge lock (Nord-lock) washers &
Serrated flange nuts are probably the best way to go.

When lives are on the line you may want to employ a 'positive locking device' such as a castle nut or a slotted nut. No amount of vibration will break this kind of connection:

Since this one is sure to stir things up when you mention it the guys at the office, I've provided my sources below.

A) Article 1 n boltscience.com and Article 2 on Boltscience.com and Article 3 on Boltscience.com, all condeming split washers
B) pdf file from hillcountryengineering.com condeming split washers
D) Awesome video showing actual testing and how preload decay charts are generated.
*E) Alternate Testing Video #1 making the counter argument in favor of split washers.
*F) Alternate Testing Video #2  making the counter argument in favor of split washers.

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#2. Double Nutted joints with jam nuts are affected by order of clamping. While I'm talking about bolt locking techniques, I'll share another interesting one: For double nut connections involving the use of a jam nut & a standard nut, it REALLY matters what order you install them in.
The jam nut should go on first! Otherwise the effectiveness of the nut pair is greatly reduced. Double nut Source.

Before I move on to the next one I need to clarify the difference between static loads and fatigue loads. Static loads do not change over time. If a bolt is rated to yield at 3,000 lbs of tension, any static load less than that will not have a permanent effect.

However, if you were to vary that applied load over time you can fatigue the bolt until it breaks using less than 3,000 lbs! In the same way that a small stream can carve out the Grand Canyon, fatigue loads gradually chip away at the structural integrity of fasteners over time.

#3. The relationship between fatigue load and the number of cycles until bolt failure occurs can be predicted using experimentation. It turns out that you can make reasonably accurate predictions of the cycle count at failure by performing as few as three experiments (though I would recommend doing at least 6 to attain some real accuracy). All it takes are a few data points and a regression line to create a high cycle fatigue life curve (aka an S-N curve).

We don't put the ultimate static loading on the graph, but if we did it would be the highest point on the 'applied load' axis and the zero point on the 'cycles' axis.

Why is this useful? Now that you know bolts can break from small fatigue loads, imagine trying to build a bridge using riveted or bolted connections. How could you trust that you ever had a big enough fastener? It turns out that fatigue loads below a certain threshold will never cause the fastener to break.

As a very general estimate, a bolt will require an infinite number of cycles to break if the fatigue load is around 30% (+/-15%) of the ultimate static load. You can expect the bolt to break in a few thousand cycles if the fatigue load is about 80% (+/-10%) of the ultimate static load. (Note: the exact percentage can vary dramatically based on material composition and ambient conditions.)

#4. (UPDATED) For maximum strength tighten bolts up to the yield point'For maximum durability, don't! There is a common misunderstanding that a bolt within a securely fastened connection is impervious to outside forces if hey don't exceed the clamped load of the connection.

That is, the myth says a bolt clamped to 500 lbs won't experience additional stress unless outside forces applied to the clamp exceed 500 lbs.  This is not so! In fact ANY additional load, no matter how small, will add to the tension in the bolt. But not at a 1:1 rate.
Think of pulling on a fastened connection as if it were 2 stacked springs. Both springs stretch measurably, but the weaker one stretches more. Part of the external load is absorbed by the joint and part by the fastener.

To be crystal clear, as you tighten the nut the bolt will compress the two parts together. The bolt itself has an internal reaction force equal to the amplitude of the compression force, but the bolt itself is in tension.  If you were to graph the tension on the bolt while you tighten the nut, the plot would look like the graph below. To get the greatest clamping force out of the bolt we would to tighten it all the way up to the yield point. Any more force and the bolt will enter the plastic region and permanently deform.

In practice engineers don't design that way. Since any additional force will begin to yield the bolt, you want to give yourself some margin for error.  Engineers select a bolt tension that is somewhere between the calculable minimum functional clamping force and the yielding force'. while also accounting for error in the tension measurement method.

(Sources: Shingley's Standard Handbook  & Article on Fastenal )

#5. It is actually quite difficult to determine the exact load the fastener sees during clamping. We now know how important it is to avoid over tightening a bolt, but how do we know when it is yielding?

For everyday purposes the clamping force can be approximated by measuring the tightening torque. You can look up the recommended tightening torque for a given fastener size in my bolt sizing calculator or in a table like the one found here.  An alternate method is called the 'turn of the nut' wherein you tighten the bolt until it 'feels snug' before rotating it another 90 degrees to ensure adequate tightness.

Those methods work OK for most things, but some critical applications require you to be certain of the clamping force (think spacecraft or large weights above your head). The torque method has difficultly accounting for friction and lubrication, but at least the torque is mathematically correlated to the clamping force. On the other hand the turn of the nut method uses rotational displacement to bypass lubrication affects, but it doesn't even consider forces at all.

There are better options though. Load indicating washers can accurately verify bolting loads by squishing open a paint sack after reaching a specific load. The drawback with these is that they only work once.  http://www.boltscience.com/pages/tighten.htm The other option comes from a company called smart bolts who came out with a fastener featuring a built-in tension indicator. This is by far the most accurate method of measuring bolt clamping load. On the other hand, a single box of these bolts can cost around 10 times as much as a standard fastener!

Neat, I just wish I could afford one.

How different tightening methods compare in terms of accuracy.

#6. If you've ever designed a part with a threaded hole, you may have wondered:'How many threads do I need to make a strong connection?' The answer is that it varies, but six at most.

Bolts actually stretch very slightly when force is applied, which causes the loading on each thread to be different. Because of this stretch, when you apply a tensile load on a threaded fastener the first thread at the point of connection sees the highest percentage of the load. The load on each successive thread decreases from there, as seen in the table below.

Additional threads beyond the sixth will not further distribute the load and will not make the connection any stronger. 

So will a bolt break before the nut strips? Yes! Nuts typically have no less than three internal threads, but nut thickness standards have been selected on the basis that the bolt will always sustain tensile fracture before the nut will strip.

#7. Have you ever seen a fastener labeled with a 2A or 3B rating and wondered what that meant?That number-letter combo is used to indicate the thread class of the fastener. Thread classes include 1-4 (loose to tight), A (external), and B (internal). These ratings are clearance fits which indicates the level of interference during assembly.

• Class 1 is a good choice when quick assembly and disassembly is a priority.
• Class 2 is the most common thread class because it offers a good balance between price and quality.
• Class 3 is best used in applications requiring close tolerances and a strong connection.
• Class 4 is precision tight, typically used for lead screws and such.

#8. All fasteners are available with either coarse or fine threads and each option has its owndistinctadvantages.
Finely threaded bolts have slightly larger cross-sectional areas than coarse bolts of the same diameter, so if you are limited on the bolt size due to dimensional constraints, choose a fine thread for greater strength. Fine threads are also a better choice when threading a thin walled member. When you don't have much depth to work with, you want to utilize their greater number of threads per inch. Fine threads also permit greater adjustment accuracy by requiring more rotations to move linearly.

On the other hand, coarsely threaded bolts are less likely to be cross threaded during assembly. They also allow for quicker assembly and disassembly, so choose these when you will be reassembling a part often. If the threads will be exposed to harsh conditions or chemicals, a coarsely threaded fastener should be considered for its thicker plating/coating. Coarse ly threaded fasteners are much more commonly available in the united states.

#9. Would you expect a bolt to be stronger or weaker at very high temperatures? How about at cryogenic temperatures?

Most people answer 'weaker' to both question, but being weaker at both temperatures doesn't even make sense when you think about it. Why would steel be strongest at whatever typical room temperature happens to be?  It's not.

As a rule, metals are strong & brittle at low temperatures and soft & ductile at high temperatures, within their solid phase temperature range. Room temperature is just another non-extreme point on the curve.

#10. You can make bolted connections more resistant to shear loads by using clever design instead of larger bolts. For maximum strength, try to use the correct thread length for the connection. In the image below you can see two connections which are identical except that the one on the right has a properly sized thread length. It exposes the bolt shank (rather than the threads) to the applied load at the connection seam.

All else remaining the same, the connection on the right will be stronger because the shank has a larger cross-sectional area and no stress concentrations.

Another clever trick is to design connections so that the applied load will be on multiple sections of the bolt, as opposed to just one section. In the images below there are two connections. The one on the right is twice as strong as the one on the left because it would have to shear the bolt off in two places to become free. Also, the single shear configuration can also lead to bending loads on the fastener and loosening of the connection (see #1).

#11. Have you ever cursed the day you were born because you just stripped out a Phillips head screw? While it is nice that Phillips screw drivers don't slip off screws like flat heads do, it's a real pain when the head can no longer be rotated because the screw head has melted into a hollow cone.

As frustrating as that is, it turns out that Phillips head screws are designed to strip out via the tapered point and rounded edges. The technical term is called a cam-out and every time it happens the relative surface motion wears out your screw.  Alternate screw heads like torx and pozidriv are specifically designed not to cam-out.

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If fascinating facts about fasteners are your thing then you should check out  Carroll Smith's 'Nuts, Bolts, Fasteners, and Plumbing Handbook' aka 'Screw to Win'. Smith's Engineer To Win is another good one. Actually every book by Carroll Smith is pure gold.

Contact us to discuss your requirements of Double Head Screw Nut. Our experienced sales team can help you identify the options that best suit your needs.