Why? There are many reasons, but a primary one is unfamiliarity with the operation and capabilities of laser systems. Other reasons, such as relatively high initial cost and concern about using lasers in a manufacturing environment are also frequently cited.

Laser welding can be used in place of many conventional welding processes, such as TIG, MIG, resistance, and electron beam to name a few. While each of these techniques has established a niche in the manufacturing world, the versatile laser welding process will operate efficiently and economically in many different applications. Its versatility will permit the laser system to be used for different welding applications such as spot and seam welding. Some laser welding systems can even be configured to do additional functions such as cutting, drilling, and serializing.

In this article, we will look at how the various laser welding processes work, and what benefits they can offer. Today, tens of thousands of lasers are used in industry for cutting, welding, drilling, marking, and numerous other applications. That number will continue to rise as engineers become more comfortable with their use. While most laser applications are dedicated to one product or process that involves high-volume, long-run  manufacturing, the versatility of the laser to supply energy to hard-to-reach spots, vary the output energy over a wide range, operate under the control of computers and robots, and put minimal heat into the part makes it ideal for flexible manufacturing operations.

Welding is a process where materials are heated to a molten state and are fused together. Lasers generate light energy that can be focused and absorbed into materials and converted to heat energy. By employing a light beam in the visible or near infrared portion of the electromagnetic spectrum, we can transmit this energy from its source to the material to be processed using fixed or fiber optic beam delivery optics. These optics can then focus the beam to a small spot with enough thermal energy to melt the material and create a weld.

What does this all mean to the manufacturing engineer? To appreciate the potential of employing lasers in welding operations, you must redefine some of the traditional approaches to viewing “efficiency” as it relates to energy conversion. The laser is a relatively inefficient converter of electrical energy in output light, with the laser achieving from 2 to 30 percent energy conversion, depending on the type of laser being used. However, because of the coherence of the beam, virtually all of this energy can be delivered and focused to a small spot, as small as a few thousandths of an inch. Consequently, for applying thermal energy to small areas, there are no methods as efficient as lasers. This ability to selectively apply energy offers many distinct advantages, not the least of which is the ability to minimize the surrounding heat affected zone.

Generally, there are three types of lasers that are commonly used in welding operation: CO₂, Nd:YAG (both lamp and diode pumped), and fiber lasers. Within the scope of this article, we will not delve into the actual laser operation theory, since our real interest is manipulating the output laser light for welding.

All three of these laser types operate in the infrared portion of the electromagnetic spectrum, and are invisible to the human eye. The Nd:YAG and fiber lasers operate in the near infrared spectral region at a wavelength of approximately 1 micron.  This wavelength is absorbed quite well by most metals. The near infrared radiation also permits the use of standard, relatively low cost, fused silica or other glass optics to achieve focused spot sizes as small as a few thousandths, depending on the laser.

The CO₂ (carbon dioxide) laser, on the other hand, operates in the far infrared portion of the spectrum at 10 microns, and has an initial absorption of only 10 to 20 percent for most metals.  carbon dioxide laser light is absorbed by normal glass optics, and therefore requires optics made from special materials.  Because the focused spot size is a function of the laser wavelength, the focused spot size will be larger.  This could be a limiting factor when making small and microwelds. The carbon dioxide laser was commonly used in the early days of the laser industry, when it was the only laser capable of power levels of 1 KW or more. Today these lasers are being replaced by the fiber laser which has a power capability of 50 KW and beyond.

Normal welds or “conduction welds” are made by using the thermal conductivity of the metals being welded to transmit the thermal energy of the laser beam. These welds are generally smooth and aesthetically pleasing, but are limited in penetration to from 2 -6 mm depending on the laser.

By using a technique known as “keyhole welding,” higher power lasers (>10⁶ W/cm²) can make deeper penetration welds. ¹  By increasing the intensity of the laser focused spot above the metal boiling point, a vaporized hole is formed in the weld puddle. This hole is filled with ionized metallic gas, and becomes an effective absorber, trapping about 95 % of the laser energy into a cylindrical volume know as a “keyhole.” Temperatures within this keyhole can reach as high as 25,000 °C, making the keyholing technique very efficient. ²  Instead of heat being conducted mainly downward from the surface, it is conducted radially outward from the keyhole, forming a molten region surrounding the vapor. As the laser beam moves along the work-piece, the molten metal fills in behind the keyhole and solidifies to form the weld. This technique permits faster weld speeds, and deeper penetration.

 

 

In arc welding, the intense heat needed to melt metal is produced by an electric arc. The arc is formed between the actual work and an electrode (stick or wire) that is manually or mechanically guided along the joint. The electrode can either be a rod with the purpose of simply carrying the current between the tip and the work. Or, it may be a specially prepared rod or wire that not only conducts the current but also melts and supplies filler metal to the joint. Most welding in the manufacture of steel products uses the second type of electrode.

 

1. Soft Soldering;

2. Hard Soldering;

3. Brazing.

There are a variety of types of welding joints, each with particular features that make it well suited to different tasks. In order to create a successful metal joint, it's essential that you choose the right type of joint for the right type of metal and for the purpose you're creating the joint to serve.
  

Butt Joints

A butt joint, also called a butt weld, is a common method used for joining pieces of metal end to end. It's typically used for pipes and pressure values as they are flat. The two pieces are connected adjoining each other with the seam in the middle.

T Joints

As you may have guessed, a T joint resembles the letter T. One piece of metal is connected to the middle of another piece at a perpendicular angle. T joints are popular in construction because they're extremely strong, especially when the weld is placed on the side of the joint where the pressure will be applied.

Corner Joints

Corner joints create a corner between pieces of metal. They can be further broken down into open and closed options. Open corner joints refer to when the pieces of metal don't sit flush together, and the space between the two need to be filled in with filler metal during the welding process. Closed corner joints refer to the two pieces sitting right next to each other. Here, the welding only needs to create a seam to hold them in place.

Lap Joints

A lap joint refers to any metal joint that relies on an overlap. They're among the strongest types of weld, although to be at maximum strength, the metal must overlap at three times the thickness of the joint.

Edge Joints

Edge joints tend to be a weaker type of welding joint, so they are more commonly used in sheet metal. Two pieces of metal are held with their edges parallel and a seam is made along this joint. If an edge joint is required for bigger or more weight-bearing construction, it can be strengthened using filler metal. 

There are a variety of types of welding joints, each with particular features that make it well suited to different tasks. In order to create a successful metal joint, it's essential that you choose the right type of joint for the right type of metal and for the purpose you're creating the joint to serve.
  

Butt Joints

A butt joint, also called a butt weld, is a common method used for joining pieces of metal end to end. It's typically used for pipes and pressure values as they are flat. The two pieces are connected adjoining each other with the seam in the middle.

T Joints

As you may have guessed, a T joint resembles the letter T. One piece of metal is connected to the middle of another piece at a perpendicular angle. T joints are popular in construction because they're extremely strong, especially when the weld is placed on the side of the joint where the pressure will be applied.

Corner Joints

Corner joints create a corner between pieces of metal. They can be further broken down into open and closed options. Open corner joints refer to when the pieces of metal don't sit flush together, and the space between the two need to be filled in with filler metal during the welding process. Closed corner joints refer to the two pieces sitting right next to each other. Here, the welding only needs to create a seam to hold them in place.

Lap Joints

A lap joint refers to any metal joint that relies on an overlap. They're among the strongest types of weld, although to be at maximum strength, the metal must overlap at three times the thickness of the joint.

Edge Joints

Edge joints tend to be a weaker type of welding joint, so they are more commonly used in sheet metal. Two pieces of metal are held with their edges parallel and a seam is made along this joint. If an edge joint is required for bigger or more weight-bearing construction, it can be strengthened using filler metal. 

There are a variety of types of welding joints, each with particular features that make it well suited to different tasks. In order to create a successful metal joint, it's essential that you choose the right type of joint for the right type of metal and for the purpose you're creating the joint to serve.
  

Butt Joints

A butt joint, also called a butt weld, is a common method used for joining pieces of metal end to end. It's typically used for pipes and pressure values as they are flat. The two pieces are connected adjoining each other with the seam in the middle.

T Joints

As you may have guessed, a T joint resembles the letter T. One piece of metal is connected to the middle of another piece at a perpendicular angle. T joints are popular in construction because they're extremely strong, especially when the weld is placed on the side of the joint where the pressure will be applied.

Corner Joints

Corner joints create a corner between pieces of metal. They can be further broken down into open and closed options. Open corner joints refer to when the pieces of metal don't sit flush together, and the space between the two need to be filled in with filler metal during the welding process. Closed corner joints refer to the two pieces sitting right next to each other. Here, the welding only needs to create a seam to hold them in place.

Lap Joints

A lap joint refers to any metal joint that relies on an overlap. They're among the strongest types of weld, although to be at maximum strength, the metal must overlap at three times the thickness of the joint.

Edge Joints

Edge joints tend to be a weaker type of welding joint, so they are more commonly used in sheet metal. Two pieces of metal are held with their edges parallel and a seam is made along this joint. If an edge joint is required for bigger or more weight-bearing construction, it can be strengthened using filler metal. 

There are a variety of types of welding joints, each with particular features that make it well suited to different tasks. In order to create a successful metal joint, it's essential that you choose the right type of joint for the right type of metal and for the purpose you're creating the joint to serve.
  

Butt Joints

A butt joint, also called a butt weld, is a common method used for joining pieces of metal end to end. It's typically used for pipes and pressure values as they are flat. The two pieces are connected adjoining each other with the seam in the middle.

T Joints

As you may have guessed, a T joint resembles the letter T. One piece of metal is connected to the middle of another piece at a perpendicular angle. T joints are popular in construction because they're extremely strong, especially when the weld is placed on the side of the joint where the pressure will be applied.

Corner Joints

Corner joints create a corner between pieces of metal. They can be further broken down into open and closed options. Open corner joints refer to when the pieces of metal don't sit flush together, and the space between the two need to be filled in with filler metal during the welding process. Closed corner joints refer to the two pieces sitting right next to each other. Here, the welding only needs to create a seam to hold them in place.

Lap Joints

A lap joint refers to any metal joint that relies on an overlap. They're among the strongest types of weld, although to be at maximum strength, the metal must overlap at three times the thickness of the joint.

Edge Joints

Edge joints tend to be a weaker type of welding joint, so they are more commonly used in sheet metal. Two pieces of metal are held with their edges parallel and a seam is made along this joint. If an edge joint is required for bigger or more weight-bearing construction, it can be strengthened using filler metal. 

There are a variety of types of welding joints, each with particular features that make it well suited to different tasks. In order to create a successful metal joint, it's essential that you choose the right type of joint for the right type of metal and for the purpose you're creating the joint to serve.
  

Butt Joints

A butt joint, also called a butt weld, is a common method used for joining pieces of metal end to end. It's typically used for pipes and pressure values as they are flat. The two pieces are connected adjoining each other with the seam in the middle.

T Joints

As you may have guessed, a T joint resembles the letter T. One piece of metal is connected to the middle of another piece at a perpendicular angle. T joints are popular in construction because they're extremely strong, especially when the weld is placed on the side of the joint where the pressure will be applied.

Corner Joints

Corner joints create a corner between pieces of metal. They can be further broken down into open and closed options. Open corner joints refer to when the pieces of metal don't sit flush together, and the space between the two need to be filled in with filler metal during the welding process. Closed corner joints refer to the two pieces sitting right next to each other. Here, the welding only needs to create a seam to hold them in place.

Lap Joints

A lap joint refers to any metal joint that relies on an overlap. They're among the strongest types of weld, although to be at maximum strength, the metal must overlap at three times the thickness of the joint.

Edge Joints

Edge joints tend to be a weaker type of welding joint, so they are more commonly used in sheet metal. Two pieces of metal are held with their edges parallel and a seam is made along this joint. If an edge joint is required for bigger or more weight-bearing construction, it can be strengthened using filler metal. 

There are a variety of types of welding joints, each with particular features that make it well suited to different tasks. In order to create a successful metal joint, it's essential that you choose the right type of joint for the right type of metal and for the purpose you're creating the joint to serve.
  

Butt Joints

A butt joint, also called a butt weld, is a common method used for joining pieces of metal end to end. It's typically used for pipes and pressure values as they are flat. The two pieces are connected adjoining each other with the seam in the middle.

T Joints

As you may have guessed, a T joint resembles the letter T. One piece of metal is connected to the middle of another piece at a perpendicular angle. T joints are popular in construction because they're extremely strong, especially when the weld is placed on the side of the joint where the pressure will be applied.

Corner Joints

Corner joints create a corner between pieces of metal. They can be further broken down into open and closed options. Open corner joints refer to when the pieces of metal don't sit flush together, and the space between the two need to be filled in with filler metal during the welding process. Closed corner joints refer to the two pieces sitting right next to each other. Here, the welding only needs to create a seam to hold them in place.

Lap Joints

A lap joint refers to any metal joint that relies on an overlap. They're among the strongest types of weld, although to be at maximum strength, the metal must overlap at three times the thickness of the joint.

Edge Joints

Edge joints tend to be a weaker type of welding joint, so they are more commonly used in sheet metal. Two pieces of metal are held with their edges parallel and a seam is made along this joint. If an edge joint is required for bigger or more weight-bearing construction, it can be strengthened using filler metal. 

There are a variety of types of welding joints, each with particular features that make it well suited to different tasks. In order to create a successful metal joint, it's essential that you choose the right type of joint for the right type of metal and for the purpose you're creating the joint to serve.

Butt Joints

A butt joint, also called a butt weld, is a common method used for joining pieces of metal end to end. It's typically used for pipes and pressure values as they are flat. The two pieces are connected adjoining each other with the seam in the middle.

T Joints

As you may have guessed, a T joint resembles the letter T. One piece of metal is connected to the middle of another piece at a perpendicular angle. T joints are popular in construction because they're extremely strong, especially when the weld is placed on the side of the joint where the pressure will be applied.

Corner Joints

Corner joints create a corner between pieces of metal. They can be further broken down into open and closed options. Open corner joints refer to when the pieces of metal don't sit flush together, and the space between the two need to be filled in with filler metal during the welding process. Closed corner joints refer to the two pieces sitting right next to each other. Here, the welding only needs to create a seam to hold them in place.

Lap Joints

A lap joint refers to any metal joint that relies on an overlap. They're among the strongest types of weld, although to be at maximum strength, the metal must overlap at three times the thickness of the joint.

Edge Joints

Edge joints tend to be a weaker type of welding joint, so they are more commonly used in sheet metal. Two pieces of metal are held with their edges parallel and a seam is made along this joint. If an edge joint is required for bigger or more weight-bearing construction, it can be strengthened using filler metal. 

We're talking away
I don't know what
I'm to say I'll say it anyway
Today's another day to find you
Shying away
I'll be coming for your love, okay?

Take on me (take on me)
Take me on (take on me)
I'll be gone
In a day or two

So needless to say
I'm odds and ends
But I'll be stumbling away
Slowly learning that life is okay
Say after me
It's no better to be safe than sorry

Take on me (take on me)
Take me on (take on me)
I'll be gone
In a day or two 

Solid rivets are used in applications where reliability and safety count. A typical application for solid rivets can be found within the structural parts of aircraft. Hundreds of thousands of solid rivets are used to assemble the frame of a modern aircraft. Such rivets come with rounded (universal) or 100° countersunk heads. Typical materials for aircraft rivets are aluminium alloys (2017, 2024, 2117, 7050, 5056, 55000, V-65), titanium, and nickel-based alloys (e.g., Monel). Some aluminum alloy rivets are too hard to buck and must be softened by solution treating (precipitation hardening) prior to being bucked. "Ice box" aluminum alloy rivets harden with age, and must likewise be annealed and then kept at sub-freezing temperatures (hence the name "ice box") to slow the age-hardening process. Steel rivets can be found in static structures such as bridges, cranes, and building frames.

The setting of these fasteners requires access to both sides of a structure. Solid rivets are driven using a hydraulically, pneumatically, or electromagneticallyactuated squeezing tool or even a handheld hammer. Applications where only one side is accessible require "blind" rivets.

Solid rivets are also used by some artisans in the construction of modern reproduction of medieval armour, jewellery and metal couture.

High-strength structural steel rivets[edit]

Structural steel rivets like this one were used in the construction of the Golden Gate Bridge in the 1930s.

Women rivet heaters, with their tongs and catching buckets, Puget Sound Navy Yard, May 1919

Until relatively recently, structural steel connections were either welded or riveted. High-strength bolts have largely replaced structural steel rivets. Indeed, the latest steel construction specifications published by AISC (the 14th Edition) no longer covers their installation. The reason for the change is primarily due to the expense of skilled workers required to install high strength structural steel rivets. Whereas two relatively unskilled workers can install and tighten high strength bolts, it takes a minimum of four highly skilled riveters to install rivets.^{[citation needed]}

At a central location near the areas being riveted, a furnace was set up. Rivets were placed in the furnace and heated to glowing hot (often to white hot) so that they were more plastic and easily deformed. The rivet warmer or "cook" used tongs to remove individual rivets and throw them to a catcher stationed near the joints to be riveted. The catcher (usually) caught the rivet in a leather or wooden bucket with an ash-lined bottom. He placed the rivet into the hole to be riveted, then quickly turned to catch the next rivet. The "holder up or holder on" would hold a heavy rivet set or dolly or another (larger) pneumatic jack against the round head of the rivet, while the riveter (sometimes two riveters) applied a hammer or pneumatic rivet hammer to the unformed head, making it mushroom tightly against the joint in its final domed shape. Alternatively the buck is hammered more or less flush with the structure in a counter sunk hole.^[1] Before the use of pneumatic hammers, e.g. in the construction of RMS Titanic, the man who hammered the rivet was known as the "basher". Upon cooling, the rivet contracted and exerted further force, tightening the joint.

The last commonly used high strength structural steel rivets were designated ASTM A502 Grade 1 rivets.^[2]

Such riveted structures may be insufficient to resist seismic loading from earthquakes if the structure was not engineered for such forces, a common problem of older steel bridges. This is because a hot rivet cannot be properly heat treated to add strength and hardness. In the seismic retrofit of such structures it is common practice to remove critical rivets with an oxygen torch, precision ream the hole, then insert a machined and heat treated bolt.

Semi-tubular rivets[edit]

A typical technical drawing of an oval head semi-tubular rivet

Semi-tubular rivets (also known as tubular rivets) are similar to solid rivets, except they have a partial hole (opposite the head) at the tip. The purpose of this hole is to reduce the amount of force needed for application by rolling the tubular portion outward. The force needed to apply a semitubular rivet is about 1/4 of the amount needed to apply a solid rivet. Tubular rivets are sometimes preferred for pivot points (a joint where movement is desired) since the swelling of the rivet is only at the tail. The type of equipment used to apply semi-tubular rivets range from prototyping tools to fully automated systems. Typical installation tools (from lowest to highest price) are hand set, manual squeezer, pneumatic squeezer, kick press, impact riveter, and finally PLC-controlled robotics. The most common machine is the impact riveter and the most common use of semitubular rivets is in lighting, brakes, ladders, binders, HVAC duct work, mechanical products, and electronics. They are offered from 1/16-inch (1.6 mm) to 3/8-inch (9.5 mm) in diameter (other sizes are considered highly special) and can be up to 8 inches (203 mm) long. A wide variety of materials and platings are available, most common base metals are steel, brass, copper, stainless, aluminum and most common platings are zinc, nickel, brass, tin. Tubular rivets are normally waxed to facilitate proper assembly. An installed tubular rivet has a head on one side, with a rolled over and exposed shallow blind hole on the other.

Blind rivets[edit]

Three aluminium blind rivets: 1/8", 3/32", and 1/16"

Animation of a rivet being tightened

Pop rivet gun with rivet inserted

Blind rivets, commonly referred to as "pop" rivets (POP is the brand name of the original manufacturer, now owned by Stanley Engineered Fastening, a division of Stanley Black & Decker) are tubular and are supplied with a mandrel through the center. The rivet assembly is inserted into a hole drilled through the parts to be joined and a specially designed tool is used to draw the mandrel into the rivet. This expands the blind end of the rivet and then the mandrel snaps off. These types of blind rivets have non-locking mandrels and are sometimes avoided for critical structural joints because the mandrels may fall out, due to vibration or other reasons, leaving a hollow rivet that has a lower load-carrying capability than solid rivets. Furthermore, because of the mandrel they are more prone to failure from corrosion and vibration. Unlike solid rivets, blind rivets can be inserted and fully installed in a joint from only one side of a part or structure, "blind" to the opposite side.^[3]

Due to this feature, blind rivets are used mainly when access to the joint is available from only one side. The rivet is placed in a drilled hole and is set by pulling the mandrel head into the rivet body, expanding the rivet body and causing it to flare against the reverse side. As the head of the mandrel reaches the face of the blind side material, the pulling force is resisted, and at a predetermined force, the mandrel snaps at its break point, also called blind setting. A tight joint formed by the rivet body remains, the head of the mandrel remains encapsulated at the blind side, although variations of this are available, and the mandrel stem is ejected.

Prior to the adoption of blind rivets, installation of a solid rivet typically required access to both sides of the assembly: a rivet hammer on one side and a bucking bar on the other side. In 1916, Royal Navy reservist and engineer Hamilton Neil Wylie filed a patent for an "improved means of closing tubular rivets" (granted May 1917).^[4] In 1922 Wylie joined the British aircraft manufacturer Armstrong-Whitworth Ltd to advise on metal construction techniques; here he continued to develop his rivet design with a further 1927 patent^[5] that incorporated the pull-through mandrel, and allowed the rivet to be used blind. By 1928, the George Tucker Eyelet company produced a "cup" rivet based on the design. It required a separate GKN mandrel and the rivet body to be hand assembled prior to use for the building of the Siskin III aircraft. Together with Armstrong-Whitworth, the Geo. Tucker Co. further modified the rivet design to produce a one-piece unit incorporating mandrel and rivet.^[6] This product was later developed in aluminium and trademarked as the "POP" rivet. The United Shoe Machinery Co. produced the design in the U.S. as inventors such as Carl Cherry and Lou Huck experimented with other techniques for expanding solid rivets.

They are available in flat head, countersunk head, and modified flush head with standard diameters of 1/8, 5/32 and 3/16 inch. Blind rivets are made from soft aluminum alloy, steel (including stainless steel), copper, and Monel.

There are also structural blind rivets, which are designed to take shear and tensile loads.^[7]

The rivet body is normally manufactured using one of three methods:

NameDescription
Wire | the most common method
Tube | common in longer lengths, not normally as strong as wire
Sheet | least popular and generally the weakest option

There is a vast array of specialty blind rivets that are suited for high strength or plastic applications. Typical types include:

NameDescription
TriFold | a rivet that splits into three equal legs like a molly bolt. Typically used in soft plastics where a wide footprint is needed at the rear surface. Used in automotive interiors and vinyl fences. (See § Oscar rivets.)
Structural rivet(a) | an "external" mechanically locked structural blind rivet that is used where a watertight, vibration resistant connection is of importance. Typically used in manufacture or repair of truck bodies. A special nosepiece is required to apply this rivet.
Structural rivet(b) | an "internal" mechanically locked structural blind rivet that is used where a watertight, vibration resistant connection is of importance. Typically used in manufacture or repair of truck bodies.

Internally and externally locked structural blind rivets can be used in aircraft applications because, unlike other types of blind rivets, the locked mandrels cannot fall out and are watertight. Since the mandrel is locked into place, they have the same or greater load-carrying capacity as solid rivets and may be used to replace solid rivets on all but the most critical stressed aircraft structures.

The typical assembly process requires the operator to install the rivet in the nose of the tool by hand and then actuate the tool. However, in recent years automated riveting systems have become popular in an effort to reduce assembly costs and repetitive disorders. The cost of such tools range from US$1,500 for autofeed pneumatics to US$50,000 for fully robotic systems.

While structural blind rivets using a locked mandrel are common, there are also aircraft applications using "non-structural" blind rivets where the reduced, but still predictable, strength of the rivet without the mandrel is used as the design strength. A method popularized by Chris Heintz of Zenith Aircraft uses a common flat-head (countersunk) rivet which is drawn into a specially machined nosepiece that forms it into a round head rivet, taking up much of the variation inherent in hole size found in amateur aircraft construction. Aircraft designed with these rivets use rivet strength figures measured with the mandrel removed.^[8]

Oscar rivets[edit]

Oscar Rivet shown with mandrel. (Dashed lines depict flare/flange after installation.)

Oscar rivets are similar to blind rivets in appearance and installation, but have splits (typically three) along the hollow shaft. These splits cause the shaft to fold and flare out (similar to the wings on a toggle bolt's nut) as the mandrel is drawn into the rivet. This flare (or flange) provides a wide bearing surface that reduces the chance of rivet pull-out. This design is ideal for high vibration applications where the back surface is inaccessible.

A version of the Oscar rivet is the Olympic rivet which uses an aluminum mandrel that is drawn into the rivet head. After installation, the head and mandrel are shaved off flush resulting in an appearance closely resembling a brazier head driven rivet. They are used in repair of Airstream trailers to replicate the look of the original rivets.

Drive rivet[edit]

A drive rivet is a form of blind rivet that has a short mandrel protruding from the head that is driven in with a hammer to flare out the end inserted in the hole. This is commonly used to rivet wood panels into place since the hole does not need to be drilled all the way through the panel, producing an aesthetically pleasing appearance. They can also be used with plastic, metal, and other materials and require no special setting tool other than a hammer and possibly a backing block (steel or some other dense material) placed behind the location of the rivet while hammering it into place. Drive rivets have less clamping force than most other rivets. Drive screws, possibly another name for drive rivets, are commonly used to hold nameplates into blind holes. They typically have spiral threads that grip the side of the hole.^[9]

Flush rivet[edit]

A flush rivet is used primarily on external metal surfaces where good appearance and the elimination of unnecessary aerodynamic drag are important. A flush rivet takes advantage of a countersink hole; they are also commonly referred to as countersunk rivets. Countersunk or flush rivets are used extensively on the exterior of aircraft for aerodynamic reasons such as reduced drag and turbulence. Additional post-installation machining may be performed to perfect the airflow.

Friction-lock rivet[edit]

These resemble an expanding bolt except the shaft snaps below the surface when the tension is sufficient. The blind end may be either countersunk ('flush') or dome shaped.

One early form of blind rivet that was the first to be widely used for aircraft construction and repair was the Cherry friction-lock rivet. Originally, Cherry friction-locks were available in two styles, hollow shank pull-through and self-plugging types. The pull-through type is no longer common; however, the self-plugging Cherry friction-lock rivet is still used for repairing light aircraft.

Cherry friction-lock rivets are available in two head styles, universal and 100 degree countersunk. Furthermore, they are usually supplied in three standard diameters, 1/8, 5/32 and 3/16 inch.

A friction-lock rivet cannot replace a solid shank rivet, size for size. When a friction-lock is used to replace a solid shank rivet, it must be at least one size larger in diameter because the friction-lock rivet loses considerable strength if its center stem falls out due to vibrations or damage.

Rivet alloys, shear strengths, and driving condition[edit]

Alloy typeAlphabetical letterDriven conditionMarking on head
PLAIN
2117 | AD | 2117T3 | DIMPLE
5056 | B | 5056H32 | RAISED CROSS
2017 | D | 2017T31 | RAISED DOT
2024 | DD | 2024T31 | TWO RAISED DASHES
7050 | E (or KE per NAS) | 7050T73 | RAISED RING

Self-piercing rivets[edit]

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Self-pierce riveting (SPR) is a process of joining two or more materials using an engineered rivet ^[10]. Unlike solid, blind and semi-tubular rivets, self-pierce rivets do not require a drilled or punched hole.

SPRs are cold forged to a semi-tubular shape and contain a partial hole to the opposite end of the head. The end geometry of the rivet has a chamfered poke that helps the rivet pierce the materials being joined. A hydraulic or electric servo rivet setter drives the rivet into the material, and an upsetting die provides a cavity for the displaced bottom sheet material to flow. The SPR process is described in here SPR process.

The self-pierce rivet fully pierces the top sheet material(s) but only partially pierces the bottom sheet. As the tail end of the rivet does not break through the bottom sheet it provides a water or gas-tight joint. With the influence of the upsetting die, the tail end of the rivet flares and interlocks into the bottom sheet forming a low profile button.

Rivets need to be harder than the materials being joined ^[11]. they are heat treated to various levels of hardness depending on the material's ductility and hardness. Rivets come in a range of diameters and lengths depending on the materials being joined; head styles are either flush countersunk or pan heads.

Depending on the rivet setter configuration, i.e. hydraulic, servo, stroke, nose-to-die gap, feed system etc., cycle times can be as quick as one second. Rivets are typically fed to the rivet setter nose from tape and come in cassette or spool form for continuous production.

Riveting systems can be manual or automated depending on the application requirements; all systems are very flexible in terms of product design and ease of integration into a manufacturing process.

SPR joins a range of dissimilar materials such as steel, aluminum, plastics, composites and pre-coated or pre-painted materials^[12][13]. Benefits include low energy demands, no heat, fumes, sparks or waste and very repeatable quality.

Sizes[edit]

Installing rivets on M3 tank hull

Rivets come in both inch series and metric series:

The main official standards relate more to technical parameters such as ultimate tensile strength and surface finishing than physical length and diameter. They are:

Abbreviation | Issuing authority
AIA / NASM | Aerospace Industries Association (AIA) Imperial Standard, NASM is an acronym for National Aerospace Standards, MIL-STD.
AN / MS | United States Military Standard used by the USA army, navy, or air force is Imperial.
ASME / ANSI | The American Society of Mechanical Engineers (ASME) 18-digit PIN code Imperial system is approved by ANSI and adopted by the U.S. Department of Defense.
BS /BSI | British Standards Institution. provides four-figure BS numbers for Imperial standards and also provides similar BS numbers for official translations into English for the Internal market of the European Union (see below: DIN or SI)
SAE | The Society of Automotive Engineers is a worldwide organization that provides (mostly Imperial) specifications for design and testing for components used in the automotive industry.
JIS | Japanese Industrial Standard (JIS) is a metric system largely based on DIN with some minor modifications to meet the needs of the Japanese market, nortably used in Japanese electronic equipment.
DIN | Deutsches Institut für Normung is the German national metric standard used in most European countries because it closely resembles the newer International Standards Organizations (ISO) specifications. DIN fasteners use a DIN style identifier plus the material and the finish or plating (if any).
ISO | International Organization for Standardization (ISO) is a worldwide metric standard. Clarified ISO standards for (metric) fasteners are rapidly gaining international recognition in preference to the similar DIN, on which SI was originally based.

Imperial[edit]

Rivet diameters are commonly measured in ​¹⁄₃₂-inch increments^[14] and their lengths in ​¹⁄₁₆-inch increments, expressed as "dash numbers" at the end of the rivet identification number. A "dash 3 dash 4" (XXXXXX-3-4) designation indicates a ​³⁄₃₂-inch diameter and ​⁴⁄₁₆-inch (or ​¹⁄₄-inch) length. Some rivets lengths are also available in half sizes, and have a dash number such as –3.5 (​⁷⁄₃₂inch) to indicate they are half-size. The letters and digits in a rivet's identification number that precede its dash numbers indicate the specification under which the rivet was manufactured and the head style. On many rivets, a size in 32nds may be stamped on the rivet head. Other makings on the rivet head, such as small raised or depressed dimples or small raised bars indicate the rivet's alloy.

To become a proper fastener, a rivet should be placed in hole ideally 4–6 thousandths of an inch larger in diameter. This allows the rivet to be easily and fully inserted, then setting allows the rivet to expand, tightly filling the gap and maximizing strength.

Metric[edit]

Rivet diameters and lengths are measured in millimeters. Conveniently, the rivet diameter relates to the drill required to make a hole to accept the rivet, rather than the actual diameter of the rivet, which is slightly smaller. This facilitates the use of a simple drill-gauge to check both rivet and drill are compatible. For general use, diameters between 2 mm – 20 mm and lengths from 5 mm – 50 mm are common. The design-type, material and any finish is usually expressed in plain language (often English).

Applications[edit]

A riveted buffer beam on a steam locomotive

A riveted truss bridge over the Orange River

Detail of a 1941 riveted ship hull, with the rivets clearly visible

Impact method for solid rivet and semitubular rivets

Before welding techniques and bolted joints were developed, metal framed buildings and structures such as the Eiffel Tower, Shukhov Tower and the Sydney Harbour Bridge were generally held together by riveting, as were automobile chassis. Riveting is still widely used in applications where light weight and high strength are critical, such as in an aircraft. Many sheet-metal alloys are preferably not welded as deformation and modification of material properties can occur.

A large number of countries used rivets in the construction of armored tanks during World War II, including the M3 Lee (General Grant) manufactured in the United States. However, many countries soon learned that rivets were a large weakness in tank design, since if a tank was hit by a large projectile it would dislocate the rivets and they would fly around the inside of the tank and injure or kill the crew, even if the projectile did not penetrate the armor. Some countries such as Italy, Japan, and Britain used rivets in some or all of their tank designs throughout the war for various reasons, such as lack of welding equipment or inability to weld very thick plates of armor effectively.

Blind rivets are used almost universally in the construction of plywood road cases.

Common but more exotic uses of rivets are to reinforce jeans and to produce the distinctive sound of a sizzle cymbal.

Joint analysis[edit]

The stress and shear in a rivet is analyzed like a bolted joint. However, it is not wise to combine rivets with bolts and screws in the same joint. Rivets fill the hole where they are installed to establish a very tight fit (often called interference fit). It is difficult or impossible to obtain such a tight fit with other fasteners. The result is that rivets in the same joint with loose fasteners carry more of the load—they are effectively more stiff. The rivet can then fail before it can redistribute load to the other loose fit fasteners like bolts and screws. This often causes catastrophic failure of the joint when the fasteners unzip. In general, a joint composed of similar fasteners is the most efficient because all fasteners reach capacity simultaneously.

Installation[edit]

Solid and semi tubular rivets[edit]

There are several methods for installing solid rivets.

Rivets small enough and soft enough are often bucked.^[15] In this process the installer places a rivet gun against the factory head and holds a bucking bar against the tail or a hard working surface. The bucking bar is a specially shaped solid block of metal. The rivet gun provides a series of high-impulse forces that upsets and work hardens the tail of the rivet between the work and the inertia of the bucking bar. Rivets that are large or hard may be more easily installed by squeezing instead. In this process a tool in contact with each end of the rivet clinches to deform the rivet.

Rivets may also be upset by hand, using a ball-peen hammer. The head is placed in a special hole made to accommodate it, known as a rivet-set. The hammer is applied to the buck-tail of the rivet, rolling an edge so that it is flush against the material.

Testing[edit]

Solid rivets for construction[edit]

A hammer is also used to "ring" an installed rivet, as a non-destructive test for tightness and imperfections. The inspector taps the head (usually the factory head) of the rivet with the hammer while touching the rivet and base plate lightly with the other hand and judges the quality of the audibly returned sound and the feel of the sound traveling through the metal to the operator's fingers. A rivet tightly set in its hole returns a clean and clear ring, while a loose rivet produces a recognizably different sound.

Testing of blind rivets[edit]

A blind rivet has strength properties that can be measured in terms of shear and tensile strength. Occasionally rivets also undergo performance testing for other critical features, such as pushout force, break load and salt spray resistance. A standardized destructive test according to the Inch Fastener Standards is widely accepted^[16][17]

The shear test involves installing a rivet into two plates at specified hardness and thickness and measuring the force necessary to shear the plates. The tensile test is basically the same, except that it measures the pullout strength. Per the IFI-135 standard, all blind rivets produced must meet this standard. These tests determine the strength of the rivet, and not the strength of the assembly. To determine the strength of the assembly a user must consult an engineering guide or the Machinery's Handbook.^[18]

Alternatives[edit]

See also[edit]

References[edit]

 

Take on me (take on me)
Take me on (take on me)
I'll be gone
In a day or two

So needless to say
I'm odds and ends
But I'll be stumbling away
Slowly learning that life is okay
Say after me
It's no better to be safe than sorry

Take on me (take on me)
Take me on (take on me)
I'll be gone
In a day or two

*Note: Bolts are fasteners that require a nut or pre-tapped hole to be installed. Screws use their threads to provide their own holding power. The terms in the industry are commonly mixed so sometimes you will see something that is called a screw or a bolt that is actually the opposite. Example: Lag Bolts and Lag Screws are the same thing. We have broken them down according to their true definition.

Hex Head Bolts are one of the more common styles of bolt. The head is hexagon shaped and the bolt has a shank with thread on the end. They are made to be used with a hexagon nut or nylon insert nut, also known as a nylock nut. 

Hex Head Bolts are commonly used for joints. The shank acts as a dowel while the head and the nut work together to clamp down on the materials being joined. We recommend using washers with your hex head bolts and nuts to spread the load on the materials and to avoid the head being pulled through. The washer also helps to protect the materials you are joining. If the bolt and nut spins while tightening it will spin on the washer. 

A soldering iron is a hand tool that plugs into a standard 120v AC outlet and heats up in order to melt solder around electrical connections. This is one of the most important tools used in soldering and it can come in a few variations such as pen or gun form. For beginners, it’s recommended that you use the pen style soldering iron in the 15W to 30W range. Most soldering irons have interchangeable tips that can be used for different soldering applications. Be very cautious when using any type of soldering iron because it can heat up to 896′ F which is extremely hot.

 

|  | Nuts |  | Washers |
| Rivets |
Concrete Anchors |  | Inserts |  | Threaded Rod |  | Retaining Rings | Types of Bolts | Carriage BoltsAlso known as a “coach” bolt, has a domed or countersunk head. The square section under the head grips into the part being fastened preventing the bolt from turning when the nut is tightened.
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| Hex Head BoltsHex tap bolts, hex cap screws, trim head hex cap screws, and hex serrated flange bolts fall under this category. They share a hexagonal head and are driven with a wrench. Referred to as both bolts and screws.
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| Machine ScrewsA machine screw is a screw or bolt with a flat point. Available in a variety of drive types and heads, they fit a wide variety of applications. Often driven into tapped holes. Used with nuts and washers, also known as “stove bolts” or “stovers”.
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| Shoulder BoltsShoulder bolts (also known as shoulder screws or stripper bolts) are machine screws with a shoulder between the thread of the screw and the head of the part. Once installed, the non-threaded portion extends out of the surface of the application site, allowing the bolts to act as dowels or shafts for moving parts. They can be installed by hand or with a socket (Allen) driver.
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| Socket Cap ScrewsSocket cap screws are available in button socket, button flange socket head, flat socket, and socket cap. Driven with a socket wrench or a hex Allen key. The term socket head cap screw typically refers to a type of threaded fastener whose head diameter is nominally 1.5 times or more than that of the screw shank diameter.
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| Socket Set "Grub" ScrewsSet screws are most often headless (aka blind), meaning that the screw is fully threaded and has no head. A blind set screw, known in UK as a grub screw, is almost always driven with an internal wrenching drive, such as a hex Allen key. Socket set screws are installed in threaded holes or inserts.
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| Square Head BoltsSquare Head Bolts are similar to hex cap screws but with a 4-sided head. This head style allows for a wrench to grip more easily onto the head of the bolt. The head also provides a larger gripping area as compared to a standard 6-sided hexagonal head.
Shop our Square Head BoltsFastener Varieties MenuTypes of Screws | Deck ScrewsOur deck screws feature a type 17 point (notched point at the tip) to aid in chip removal during thread cutting which allows for an easy installation in wood and composite deck materials. A bugle head and square drive help to eliminate the stripping effect sometimes experienced with other types of drives.
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| Hex Lag ScrewsLag screws, also called lag bolts, are large wood screws. The head is external hex and are driven with a wrench. Used for lag together lumber for framing, machinery to wood floors, and other heavy duty applications.
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| Self-Drilling ScrewsSelf-drilling screws have a sheet metal thread with a self-driller cutting (TEK) point to pierce through 20 to 14 gauge metals. The higher the TEK number, the larger the drill point to pierce heavier gauge metals.
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| Sheet Metal ScrewsSheet metal screws (SMS) have sharp cutting threads that cut into sheet metal, plastic or wood. They have a fully threaded shank and sometimes have a notched point at the tip to aid in chip removal during thread cutting.
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| Wood ScrewsWood screws are partially threaded with large cutting threads and a smooth shank. They are designed to slide through the top piece of wood and tightly pull all boards together.
Shop Wood ScrewsFastener Varieties MenuTypes of Nuts | Cap NutsThe cap nut, also known as the acorn nut, gets its name from its shape. The nut has a domed top to prevent contact with the external thread.
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| Castle NutsUsed with cotter pins to prevent loosening, a castellated nut, also called a castle or slotted nut, is a not with slots cut into the top. Used in low-torque applications such as holding a wheel bearing in place.
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| Coupling NutsA coupling nut is a threaded fastener used for joining two male threads, most commonly threaded rod. The outside of the fastener is a hex so it can be driven with a wrench.
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| Flange Serrated NutsA flange nut is a nut that has a wide flange at one end which acts as an integrated washer that does not move or spin. The serrated flange distributes the pressure of the nut over the part being secured and creates a locking action to prevent loosening.
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| Hex Finish NutsHex finish nuts are used for fastening to a hex cap screw, socket cap screw or bolt. The most common nuts, hex finish nuts are hex shaped with internal threads and driven with a wrench.
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| Hex Jam NutsA jam nut is often used when a nut needs to be locked in place without clamping to another object. Hex jam nuts are hex shaped with internal threads, but they are thinner than hex finish nuts.
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| Heavy Hex NutsLarger, heavier, and thicker than a standard hex nut. Heavy hex nuts are hex shaped, internally threaded, and driven with a wrench. Often used with hex cap screws and carriage bolts.
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| Hex Machine NutsA machine nut is hex shaped with internal threads. Smaller than a hex jam or hex finish nut, they are used with machine screws under 1/4" diameter.
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| Hex Machine Nuts Small PatternA machine nut is hex shaped with internal threads. Smaller than a hex jam or hex finish nut, they are used with machine screws under 1/4" diameter.
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| Keps-K Lock NutsAlso known as a keps nut, a k-nut or a washer nut, a keps-k lock nut has an attached free spinning lock washer. Keps nuts are designed to make assembly more convenient.
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| Knurled Thumb NutsA knurled head thumb nut or thumb nut has a knurled outside surface rather than a hex, which facilitates tightening by hand. Often used in decorative finishes or applications.
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| Nylon Hex Jam NutsA low-profile lock nut is hex shaped, internally threaded with a nylon insert. The nylon material prevents loosening from vibration and cross threads to stop the nut from backing off of the fastener.
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| Nylon Insert Lock NutsA nylon insert lock nut is hex shaped, internally threaded with a nylon insert. The nylon material prevents loosening from vibration and cross threads to stop the nut from backing off of the fastener.
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| Prevailing Torque Lock Nuts (Stover)Commonly known as stover nuts, prevailing torque lock nuts have chamfered corners and a conical top. The distortion in the top threads resists loosening from vibration. Also called one-way nuts, they can only be installed one way and are often used in high temperature application because they are all metal with no nylon insert.
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| Square NutsA four-sided nut that may be flat or beveled on top. Square nuts provide a greater surface contact area which provides more resistance to loosening. Typically mated with square head bolts.
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| Structural Heavy Hex NutsStructural hex nuts are comparable to finish nuts but are made to be thicker and much stronger. They are typically used in steel to steel structural connections.
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| T-NutsA t-nut or tee nut is used to fasten wood, particle or composite board leaving a flush surface. A long thin body with a flange at one end resembles a T in profile. T-nuts often have 3 or 4 prongs that sink into the surface providing better retention.
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| Break Away or Shear NutsShear nuts are cone nuts with a hexagonal gripping point. They are designed with an intentional flaw to snap the hexagonal head off once the maximum torque is reached. Leaving behind a protective cone nut that cannot be easily removed.
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| Tri-Groove NutsTri-groove security nuts have a tapered diameter making them difficult to grip with grabbing devices such as adjustable wrenches or pliers. These nuts require a special unconventional gripping device to install them making them more secure than a typical nut.
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| Wing NutsWing nuts are threaded nuts with wings on each side of the body allowing for manual turning and installation. Easy hand assembly and used when the nut needs to be removed often.
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| Backup Rivet WashersRivet backup washers are used to create a larger install diameter giving the rivet a better hold and more support. Backup washers can help to prevent pull-through of a rivet.
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| Belleville Conical WashersBelleville conical washers are a type of washer that adds extra tension to a fastener assembly. They are commonly used in stacks to increase the load, deflection or both to an assembly depending on the stack. These washers can be considered lock washers because they add tension and absorb vibration to an assembly.
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| Dock WashersDock washers are heavy duty washers, often used to build docks. Also used in heavy duty construction where a thick washer is needed, dock washers are similar to fender washers with a small inside diameter hole.
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| Fender WashersFender washers are round washers with a small inside diameter hole. Fender washers are used to prevent pull-through and provide a greater bearing surface under the fastener.
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| Fender Washers - Extra ThickFender washers are round washers with a small inside diameter hole. Extra thick fender washers are thicker than standard fender washers and are used to prevent pull-through and provide a greater bearing surface under the fastener.
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| Finishing Cup WashersFinishing cup washers form a cup for the head of the screw or fastener to fit in, creating a finish flush with the top of the head. Used for finishing, cup washers are shaped like a cup.
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| Flat WashersFlat washers are round outer diameter thin plates with a center hole punched to the size of the bolt or screw. Flat washers are used to distribute loads of threaded bolts, screws and nuts evenly as the fastener is tightened.
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| Flat Washers - Extra ThickExtra thick flat washers thicker than standard flat washers. These washers are round outer diameter thin plates with a center hole punched to the size of the bolt or screw. Flat washers are used to distribute loads of threaded bolts, screws and nuts evenly as the fastener is tightened.
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| Flat Washers - Military StandardMilitary standard (MS) flat washers go through extensive inspection for chemical, physical and dimensional qualities. MS washers must meet specific inner diameter and outer diameter specifications.
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| Flat Washers - 900 SeriesFlat washers in the 900 series are round and thinner than a standard flat washer with a smaller inside and outside diameter.
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| Lock Washers - Split RingSplit ring lock washers are used to prevent nuts, bolts and screws from vibrating loose. These washers are rings which are split at one point and bent into a helical shape.
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| Lock Washers - High CollarHigh collar lock washers are designed to fit under the head of a socket cap screw. Split ring lock washers are used to prevent nuts, bolts and screws from vibrating loose. These washers are rings which are split at one point and bent into a helical shape.
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| Lock Washers - External ToothExternal tooth lock washers are used for locking and tension. Round washers with teeth on the outside, used for maximum holding power. Must be used with fasteners with adequate head diameter.
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| Lock Washers - Internal ToothInternal tooth lock washers are used for locking and tension. A round washer with internal teeth, designed to prevent a nut or screw head from loosening with the strut action created by the teeth.
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| NAS WashersNAS washers are round washers with a smaller inner and outer diameter. Often used in military applications because of the strict measurement specifications.
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| Neoprene EPDM WashersRound washers that are slightly beveled with a neoprene lining. Often used with sharp point and self-drilling TEK screws to make a watertight seal around the screw or metal roofing or siding.
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| Structural WashersStructural washers are thick and strong, built for heavy duty applications such as construction. These washers can be found in steel beams and girder fastener assemblies.
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| Square WashersSquare washers are square in shape and may be flat on both sides or flat on one side and beveled on one side. Often used with square head bolts, square washers prevent pull through and provide a larger surface area and greater hold than standard round flat washers.
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