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What Are Structural Rivets?

What Are Structural Pop Rivets?

Structural pop rivets (structural blind rivets) are rivets that are specially designed with a locking mechanism to hold the mandrel in place. Before we talk about how exactly a structural pop rivet works, we should begin with how pop rivets in general work.

Pop or Blind rivets are comprised of two parts: the hat and the mandrel. A rivet hat is the portion of the rivet that deforms and stays in the installation. The mandrel is the portion of the rivet that is pulled into the rivet and mostly removed. A standard pop rivet mandrel has a designed flaw near the base of the mandrel which makes it easier to snap.

To install a rivet, first a hole needs to be drilled into the two materials. The hole should be just wide enough for the rivet hat to fit into. Once the rivet is sitting in the two materials, a rivet installation tool is used to pull the mandrel through the rear of the hat while keeping the hat pressed firmly against the installation surface. As the mandrel is pulled into the hat it deforms the back of the hat causing it to widen and pull firmly up against the rear of the installation surface. Once the torque is reached the weakened point of the mandrel will snap resulting in a complete rivet installation.

How Do Structural Rivets Work?

Structural Blind Rivet Diagram

Structural rivets work slightly different from the typical blind rivet. A structural blind rivet has a built-in (internal) locking mechanism that is designed to hold the mandrel inside of the rivet after the exposed portion snaps. This is commonly referred to as an interlock rivet. Notice how in the diagram to the right, the portion of the mandrel to the left of the hat is also much larger in a structural rivet than in a standard pop rivet.

There are several reasons structural rivets keep the mandrel locked inside the hat once installed:

  • Increased Shear Strength
  • Increased Pullout Strength
  • Higher Resistance To Vibrations
  • In some cases, they are also said to be considered weather-proof

How To Install Structural Rivets

Installing a structural blind rivet can be done basically the same way as installing a standard pop rivet:

  1. Line up the two installation materials
  2. Choose the appropriate drill bit to match the diameter of the structural rivet
  3. Drill a hole through both materials
  4. Insert the rivet through both materials into the hole
  5. Attach a rivet installation tool onto the mandrel
  6. Activate the tool to draw the mandrel out towards the installation surface
  7. Once the mandrel snaps it is completely installed

How To Remove Structural Rivets

Removing a structural rivet is just as simple as removing a standard blind rivet. To remove a structural rivet:

  1. Punch a starting hole into the center of the rivet
  2. Get a drill bit that is the same diameter as the hole originally drilled
  3. Add some lubricant to the drill bit
    1. *If the rivet is spinning, cover it in tape to prevent it from spinning
  4. Drill through the rivet with the drill bit until it goes completely through the hole

Common Industry Uses For Structural Rivets

  • Commercial Vehicles
  • Sheet Metal
  • Electrical
  • HVAC
  • Agricultural Equipment

Common Pop/Blind Rivet Installation Tools

Hand Operated Riveter
Hand Riveter
Industrial Lever Riveter
Industrial Lever Riveter
Battery Operated Riveter
Battery Operated Riveter
Pneumatic Riveter
Pneumatic Air Riveter

*Pro Tip: Rivet measuring can be quite confusing try using an Rivet Gauge or our all-encompassing Rivet Guide to answer all of your rivet questions!

Well Nuts: What Are They And How Are They Used?

What Are Well Nuts?

well nuts pre-installation

A Well Nut is a removable rivet nut made of two parts. A flanged rubber portion made of EPDM Neoprene and a brass insert nut. Well nuts only require one side of the hole to be exposed so they can be used for blind fastenings.

How Do Well Nuts Work?

A well nut, also called a rubnut, rubber nut or rawlnut, is a fastener used when something needs to be connected to a surface (in most cases where only one side is available).

Installing well nuts is a simple task:

  1. A hole must be drilled into the installation material. The hole will need to be the diameter of the rubber portion of the insert.
  2. Then slide the insert into the hole so that the flange is the only portion of the nut exposed. At this point, a hole must be drilled into the material you wish to attach if it has not been drilled already.
  3. Slide a washer onto the machine screw. You want to use a washer to press down on the flange portion of the well nut. Otherwise, the well nut will try to spin during installation.
  4. Line up the two holes and insert a machine screw that matches the threading of the well nut.
  5. Begin driving the machine screw (and washer) into the threads. As the well nut tightens, the rubber portion will start to deform and pull against the back of the installation surface creating a tight strong hold.

Are Well Nuts Waterproof?well nut after being installed

One of the most common questions about well nuts is “are they waterproof?” Yes, well nuts are considered to be a waterproof fastener but it is more accurate to call them water-resistant. Well nuts create a waterproof hole by tightly pressing the deformed rubber over and into the hole to completely seal it.

There are several ways in which they will not create a waterproof seal:

  • If the Rubber on the nut dries out
    • Rubber will eventually dry out causing cracks in the nut. This can cause leaks and will eventually need to be replaced. Time to replacement will vary but salt water environments may decrease the life of the rubber.
  • If the nut becomes submerged in deep depths
    • Even though these nuts are considered to be waterproof, after a certain depth the pressure buildup on the fastener may cause the rubber to deform further and lose its seal on the hole.
  • If the screw loosens on the nut
    • Screws can loosen over time due to accidental shocks and vibrations. If the screw begins to loosen, the rubber will begin to retake its original shape and break the seal on the hole. We recommend using a threadlocker solution when installing fasteners to prevent accidental loosening.

What Are Well Nuts Used For?

Well nuts are mostly prized for their water resistant, marine grade and blind fastening properties but can be used in many different situations. These blind insert rivet nuts can be used to deter vibrations and shocks in machinery. They are also quite common in compressors and mirrors for similar reasons.

Well nuts also provide a unique quality most fasteners do not. They can act as an insulator between two materials to prevent galvanic corrosion from occurring.

Well Nuts Vs. Rivnuts

Well nut benefits:

  • Water Resistant
  • Marine Grade
  • Blind Fastening
  • Deter Negative Effects Of Vibrations and Shocks
  • Easily Replaceable

Rivnut Benefits:

  • Many Different Materials
  • Blind Fastening
  • Significantly Stronger Pull-Out Strength

*Pro Tip: While well nuts are an excellent and versatile fastener, their grip is almost exclusively based off of the deformed rubber forming a hold over and inside of a hole. Due to this, well nuts have a weaker pull-out strength than many other fasteners and this consideration should be weighed when preparing for an installation.

Double Expansion Anchors – How Do You Use Them

What Is A Double Expansion Anchor?zinc double expansion anchors

A double expansion anchor is a type of masonry anchor used for anchoring into materials of questionable strength or quality. In the world of masonry anchors, most rely on deforming a portion near the bottom of the anchor once inside a hole to prevent the anchor from coming loose.

Double expansion anchors differ from other masonry anchors. Instead of the bottom portion of the anchor expanding dramatically to create a strong grip, the entire anchor expands, but only slightly, in size to distribute the pressure over the entire surface area of the anchor.

When Do You Use One?

Basically, most masonry anchors are one way entry devices; they’re not meant to come out. In large slabs of concrete, most of these anchors work fine because the concrete is so strong that the anchors can place a large amount of force against it without risk of damaging the concrete. This becomes a problem with certain masonry materials.

Brick is a perfect example of a softer small masonry material. Due to its size and shape, brick can be considered delicate. Common expansion anchors placed in brick will almost certainly crack or damage the brick.

A double expansion anchor would be used when the material being installed in is of a weak material or of questionable quality. They expand evenly and distribute their holding power over the entire hole. This minimal expansion over a much wider surface area still provides a strong holding power that does not damage the brick.

double expansion anchors pre and post expansion

Installing A Double Expansion Anchor

To install a double expansion anchor, follow the steps below:

  1. Using an SDS drill bit, drill a hole into the brick the same diameter as the anchor. The hole will need to be slightly longer than the anchor in-depth.
  2. After cleaning out and debris from the hole, insert the double expansion anchor into the hole with the threaded portion near the bottom.
  3. Next drill a hole through the material that will be anchored to the brick.
  4. Line up the holes and use a matching machine screw to catch the threads of the anchor. The initial spins can be done by hand.
  5. Using a screwdriver, tighten the machine screw until it tightens against the surface of the material being connected to the brick. *Note: The length of the machine screw will vary depending on what you are attaching to the brick.

One of the unique things about double expansion anchors is that they can be easily removed from an installation hole and reused. To remove one simply take out the machine screw and it will form back into its original shape. Then it can be removed from the hole.

Cotter Pins: What Are Cotter Pins?

How Do Cotter Pins Work?cotter pins

A cotter pin acts as a locking mechanism and can be used in many different situations. Cotter Pins are a simple to use fastener that require nothing more than a bolt with a hole in it (and a drill if the bolt does not have a hole), a pair of pliers and a castle nut.

How To Install A Cotter Pin

Installing a locking pin is a simple process:

  1. Attach the castle nut to the bolt and fasten it into place.
  2. Make a mark on the bolt or leave the castle pin installed.
  3. Using a drill and bit, drill a hole into the bolt at this point straight through the cross section of the bolt. You can make a starting point by using a metal punch.
  4. Remove any metal filings from the hole and insert the cotter pin.
  5. Using pliers, bend the ends of the cotter pin away from each other so the cotter pin cannot come out of the hole.

Pro Tip: When bending the cotter pin, try to round the points to look back in at the fastener. This will prevent them from catching on anything accidentally.

To Watch The Installation Of A Cotter Pin Check Out The Video Below:

Are Cotter Pins Necessary?

Cotter pins, while not considered necessary to every installation, may be necessary depending on the application. For example: A motorcycle front wheel is often held on by a castle nut and a cotter pin as it is subject to intense constant vibrations.

How Are Cotter Pins Measured?

Cotter pins have two measurements that matter for an installation. To choose the correct cotter pin you need to know the diameter and the length of the pin.

To determine the length of the cotter pin measure from the base of the rounded portion (“the eye”) to the end of the shorter side.

To determine the diameter of the cotter pin measure both pins together. The rounded portion is not supposed to fit through the hole so the hole should not be bigger than the eye.

cotter pin measurement diagram

Are Cotter Pins Reusable?

Cotter pins can be made from several different materials that are soft enough to bend. Typically, when deforming the pin once, the pins keep their strength and provide a strong locking mechanism that can be relied on.

As a general rule, cotter pins should not be reused as the extra bending weakens the pin. This can lead to the pin failing where a fresh pin would not resulting in a broken lock allowing the nut to spin loose.

How To Remove A Cotter Pin

Removing a cotter pin is an extremely simple task. Simply use pliers to bend the arms of the pin back straight enough to squeeze through the hole. If the pin is worn, these arms may simply snap off and then the rounded eye portion can simply be pulled out and replaced with a new one.

Why Should You Use A Cotter Pin

Cotter pins are used in many different installations. They can act as a quick locking mechanism that is easy to remove and replace but their main benefit is that they will prevent a nut from coming loose due to vibrations of any kind.

While many varieties of lock nut exist that are quick to install, they all come loose over some amount of time depending on how strong the vibrations are. A cotter pin completely removes the chance of a nut loosening unless the force acting on the nut is strong enough to shear through the pin.

Fasteners In Salt Water Environments: What You Need To Know

Fasteners In Salt Water Environments

One of the biggest complaints we hear about are fasteners rusting prematurely. The first question we are likely to ask is “Are you within 20 miles of a salt water environment?”

Surprisingly, an overwhelming amount of customers say yes. It is commonly understood that metal rusts and that it rusts worse in corrosive environments. It is not commonly understood that those environments spread beyond what the eye can see, however, this should be one of the bigger factors taken into consideration when buying fasteners.

Stainless steel is a prime example of this. Almost anyone you talk to can tell you stainless steel is corrosion resistant, but did you know that grade 410 stainless steel is less corrosion resistant because it is heat-treated to be harder? or that grade 304 stainless is not suited for highly corrosive environments?

In fasteners, the material and sometimes even the grade matter when it comes to choosing the right fastener for your installations. There are several materials that do extremely well in salt-water environments, some that kind of work and some that are almost guaranteed to fail.

What You Should Use

fasteners for salt water: aluminum, silicon bronze, 316 stainless steel

There are generally a few materials that work extremely well in salt-water environments. Depending on your needs you should aim to choose from the following:

  • Grade 316 Stainless Steel
  • Aluminum
  • Silicon Bronze

These materials (or specific grades) are ideal for salt-water environments because they can resist the corrosive effects that salt-water very well.

Another option to try is HDG (Hot Dip Galvanized) fasteners. HDG is a form of zinc coating that will protect the fastener from harm and is usually a cheaper option but is not a perfect solution.

HDG fasteners can handle well in certain salt-water environments but results can vary depending on if they are submerged, water temperature and air temperature. Due to these factors, we do not recommend it as it will likely not perform as well as the materials listed above.

Pro Tip

Although 316 stainless steel and aluminum are both listed as good materials to use in corrosion resistant environments, you also do not want to mix the two. If you do, the process of galvanic corrosion is more than likely to occur, resulting in a significantly shortened lifespan for your fasteners.

To see the fasteners we carry in these selections check out our marine grade and aluminum fasteners pages.

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