The term “solar fasteners” is used to describe any fasteners used to install a solar power system. Typically, solar fasteners are standard parts that are used in other industries besides solar. Sometimes a solar company will design a custom fastener specific to their system. Different types of fasteners may be required depending on the method of installation.

To start; a fastener is a piece of hardware that affixes two or more objects together. Solar power design uses two broad categories of fasteners: mobile fasteners and permanent fasteners.

Mobile fasteners are bolts, nuts, washers, and some screws. Those fasteners are designed to create a temporary union between two objects. This temporary union means you can remove these fasteners without causing damage to the assembly. Rivets, welds, lockbolts and some screws are considered permanent fasteners, designed to create a permanent assembly between two objects. This means that if you remove one of these fasteners, you’ll cause damage to the union. The correct fastener will be dictated by the design of the solar system.

Extreme environmental conditions are frequently present at the location of a solar power installations. Solar fasteners need to be durable enough to maintain the structural integrity of a PV (photovoltaic) system. Choosing the right fastener, in right material, with the right coating, will help ensure the longevity of the joint.

Washers can be plated or finished with a variety of coatings, ranging from the highly corrosion resistant DURA-CON coating to more simplistic metallic or painted finishes. Washers are sometimes coated for functional purposes, and sometimes for purely aesthetic reasons. Whatever the reason for using a particular coating or finish on a washer, we’re here to help to understand which would be best for your application. Let’s start with the three most common finished applied to washers.

Zinc / Trivalent Zinc

The most popular commercial platings, zinc is both economical and corrosion resistant, commonly used in environments where excessive moisture will not be present. On top of the zinc, a clear chromate finish is applied to create an additional layer of protection against white oxidation spots that can form in the presence of moisture. The most common way of applying zinc coatings to fasteners is through electroplating.

Black Oxide

Black oxide is a "conversion coating", meaning it is formed by a chemical reaction with the metal to form an integral surface, as opposed to an "applied coating" like zinc which bonds to the metal. A post-coating oil finish is typically applied to inhibit the development of rust.

Galvanized

Hot dip galvanizing can be highly effective as a method to apply a sufficient thickness of zinc for corrosion protection in particularly harsh environments. Steel reacts with molten zinc during the galvanizing process, which forms layers of zinc-iron alloy that are bonded metallurgically with the steel surface. The hard barrier created during this process not only resists mechanical damage, but also has a very low rate of corrosion.

If you have further questions about finishes for washers, please don’t hesitate to contact us for more information.

Certain applications require specialty washers that don’t necessarily fit into one of the earlier specified categories of flat washers, spring washers, lock washers and structural washers. Here we will look at three of the most common specialty washers used in industrial applications.

Tab Washers

Tab washers are a less common type of lock washer, featuring a tab that can be bent up against the flat of a bolt head or hex nut, thereby preventing rotation of both the washer and bolt or nut. The tabs on these types of washers can be internal or external, can have one tab or multiple tabs, and can be manufactured in large outer diameters of up to 12 inches.

Slotted Washers (C Washers)

Slotted washers feature a slot in the side that creates the appearance of the letter C and allows the user to install and remove the washer without completely disassembling the joint. Slotted washers can be used in a variety of ways, but are often used as shims or as a way to increase productivity in the process of repositioning an assembly.

Finishing Washers (Countersunk Washers)

Finishing washers, also known as countersunk washers, are used primarily for decorative appearance. A countersunk screw can be recessed into the finishing washer to create a flush, flat surface, therefore also creating a very clean appearance.

If you have further questions about specialty washers, please don’t hesitate to contact us for more information.

The term structural washer is generally inclusive of washers used in an assembly with structural bolts, or any assembly that is integrative to the structural integrity of an engineered joint.

Load Indicating Washers (Direct Tension Indicator Washers - DTI)

Load indicating washers were developed in the 1960s and contain raised protrusions that collapse as an assembly is tightened. To develop the correct tension, these washers should be used when installing A325 or A490 structural bolts. Both of the most common load indicating washer, standard DTIs and Squirter™ DTIs, are made to meet the specifications of ASTM F959.

Square Washers

Square washers look exactly as they, shaped like a square to fit into channels and slots. The flat sides prevent the washers from rotating in an assembly, and are thicker and wider than common round washers, helping to distribute heavy loads more evenly.

Cross Bracing Washers (Hillside Washers)

Cross bracing washers, also known as hillside washers, are used when connecting structural beams to cross-bracing rods or cables. These washers feature a curved top surface that allows rods to pass through and a nut to be secured at different angles, while the flat bottom side sits flush against structural beams. Cross bracing washers also contain a locking tab that make them stay in place when force is applied.

Malleable Washers

Malleable washers are cast iron round washers most commonly used in wood dock construction. The large bearing surface of these oversized washers prevents nuts and bolt heads from pulling into their wood substrate.

If you have further questions about structural washers, please don’t hesitate to contact us for more information.

Spring washers have flexibility that is utilized to prevent loosening during vibration. They are “sprung” in order to maintain a consistent preload on the adjacent fastener as the joint experiences movement.

Split Lock Washers (Helical Washers)

Split lock washers, or helical washers, looks like a ring with uneven ends. When tightened, these ends flatten to add tension to an assembly, thereby preventing the joint from loosening as a result of vibration. Split lock washers are used in a wide array of applications, but if your application is likely to experience extreme vibration, it might be better to consider a wedge washer or other type of lock washer.

Conical Washers (Dish Spring Washers)

Known by many different names, including conical spring washers, cupped spring washers, Belleville washers and more, conical washers create a very compact spring due to their shell-like shape. Conical washers are unique in their ability to be stacked, either in the same direction to create increased spring stiffness, or in the opposite direction to create increased range of motion.

Wave Washers

Wave washers have been pressed to create a wavy pattern, which acts as a spring when compressed with a threaded fastener. Due to their relative lightness, wave washers produce low preload forces.

If you have further questions about spring washers, please don’t hesitate to contact us for more information.

Apart from the variety of standard flat washers covered in our last article, the next most common type of washers are lock washers. Lock washers contain mechanisms that prevent bolts and nuts from loosening in the face of torque and vibration, thereby creating their namesake “lock” on the assembly.

Internal Tooth Lock Washers

Internal tooth lock washers feature a series of “teeth” extending inward that “bite” into the bearing surface. The teeth help prevent a bolt head or nut from loosening, but also aid in absorbing shock and vibration.

External Tooth Lock Washers (Star Washers)

External tooth lock washers, sometimes known as star washers, feature teeth on the outside of the washer ring that bite into the bolt or screw head. For these washers to work properly, they should be used with screws and bolts that have larger diameter heads, such as pan head and button head fasteners.

Internal / External Tooth Lock Washers

These types of washers are exactly what they sound like, a combination of internal teeth and external teeth, and are often used in electrical bonding. Internal / external tooth lock washers are helpful when trying to span elongated holes, but can also be used between adjustable pieces of an assembly to help maintain the position of the components after the original tightening.

Wedge Washers

Wedge washers, or beveled washers, have serrations on one bearing face and are used in a pairing. The serrated face of each washer is paired against the serrated face of the other in the pair, causing them to indent into the nut and stopping the possibility of rotation. Wedge lock washers are commonly used in construction equipment, railroad, automotive, solar and wind power applications.

If you have further questions about lock washers, please don’t hesitate to contact us for more information.

For the next installment of our Everything but the Bolt educational series, we’ll be digging into the various types of washers available for industrial uses. Some applications will only require a basic flat washer, while some applications will require a very specific type of washer, either for functionality or to adhere to certain code requirements.

The most common type of washer is a basic round flat washer, also known as a plain washer. Flat washers used in conjunction with bolts provide a smoother bearing surface on the underside of the bolt head or nut.

USS Flat Washers

USS flat washers were developed as a standard (the USS is the abbreviation for United States Standard) for basic engineering requirements in most industrial applications. The specifications of Outer Diameter (OD), Inner Diameter(ID) and Thickness (Th) are made to appeal to the widest use and highest stability, allowing users to create extreme tightness at the joint in which they are being used.

SAE Flat Washers

SAE flat washer specifications were developed specifically by the Society of Automotive Engineers to meet automotive manufacturing requirements in a broad sense. They typically have smaller outer diameters and less thickness than their USS counterparts. Although SAE washers are mostly used in automotive applications, they are also recommended for use any time the assembly includes Grade 5 or Grade 8 hex cap screws.

Fender Washers

Fender washers offer an outside diameter, and therefore bearing surface, that is much larger than that of USS flat washers. The large outside diameter design helps to better distribute applied forces when tightening an assembly. Fender washers are most commonly used in sheet metal, plumbing, automotive and electrical applications.

Thru Hardened Washers

Thru hardened washers provide additional strength and protection by going through a process of hardening or carburizing. While typically of a smaller size than standard USS washers, hardened washers are recommend for us with Grade 8 bolts, as well as other heat-treated fasteners.

ANSI Washers

ANSI washers are flat washers that meet standard provided by the American National Standards Institute (ANSI). Type A washers take into consideration both narrow and wide sizes, while Type B washers come in narrow, regular and wide sizes. Though the difference between the two types can be very minimal, the precise sizing can come in handy for applications where the washer dimensions are critical to an assembly’s functionality.

If you have further questions about flat washers or plain washers, please don’t hesitate to contact us for more information.

In our last installment of Know Your Nuts, we’re reviewing some of the less common but still very important specialty nuts available for niche uses. All specialty nuts have a particular use case in which they excel, whether they’re being used for security, to overcome an engineering hurdle, or for a specific industry. Below are examples of several specialty nuts that may be beneficial to you when designing your fastened connections.

Coupling Nuts

Coupling nuts are threaded fasteners for joining two male threads together, such as threaded rods, pipes and other parts, including those with different sized parts. Coupling nuts can also be used to extend rod assemblies to longer length from shorter components. When a right hand/left hand coupling nut is required, the part needed is known as a sleeve nut.

Cage Nuts

Cage nuts typically consist of a square nut encased in a spring steel cage with wings that can be used to compress and release the nuts. Also known as captive nuts or clip nuts, the most common use of cage nuts is in different types of equipment racks and mounting rails.

Castle Nuts

Castle nuts, or castellated nuts, have grooved heads that align with holes in a mated bolt, allowing a cotter pin to be inserted and therefore locking the nut in place. Installed like a traditional hex nut, the castle nut is commonly used in low torque applications as a simple to use, low-cost means of protection against loosening caused by vibration.

Weld Nuts

Weld nuts are a type of specialized nut engineered specifically for the purpose of being welded to another metal component. Weld nuts are helpful when a very high strength connection is needed in an application with limited space. Weld nuts come in a variety of shapes, including square, round, tabbed and flange. Since weld nuts need to be welded, they usually come uncoated, to be painted or finished later after the welding is completed.

Wheel Nuts

A wheel nut, more commonly known as a lug nut, serves the specific purpose of securing a wheel to a vehicle. Automobiles, trucks, and other large vehicles with rubber tires are the most typical applications for wheel nuts.

Rivet Nuts

Rivet nuts, also known as blind rivet nuts or rivnuts, are one-piece internally threaded and counterbored tubular rivets. Rivet nuts are a type of threaded inserts, and can be anchored entirely from one side. One form of rivets nuts are designed to bulge on the back side as a fastener is tightened, locking the assembly into place. Rivet nuts are most commonly used in applications where the substrate is too brittle or thin for regular hole tapping, especially in tubing for electronics, aerospace and more.

Self-Clinching Nuts

Self-clinching nuts, also called swage nuts, provide a great solution for design engineers when a strong reusable thread is needed for their application. Self-clinching nuts can fasten softer materials permanently by anchoring into the material, and are often used in sheet metal and cable railing assemblies.

Tri-Groove Nuts

Tri-Groove nuts belong to a family of specialty fasteners known as “security fasteners” or “tamper-proof fasteners” and are commonly used in public applications like parks, campgrounds and community centers. Tri-Groove nuts are installed using a unique socket designed to grip the indentations on the outer body of the nut, allowing it to be turned along the threads. It’s typical for these security fasteners to be used with driver-less fasteners, like carriage bolts and concrete anchors, ensuring a fully tamper-resistant assembly.

Break Away Nuts

Break away nuts, or shear nuts, are another type of security fasteners used in assemblies where tampering could be a concern. These conical-shaped nuts feature a hexagonal gripping point, and are designed to allow the hex head to snap off, or “break away”, once the maximum torque is reached. What remains is a protective cone nut that is tamper-proof and extremely difficult to remove since nothing remains to be gripped.

If you have further questions about specialty nuts, please don’t hesitate to contact us for more information.

Next up in our educational series called Know Your Nuts, we’re talking about different types of shaped nuts. The use of shaped nuts varies from type to type, but in general, they all share some aspect of their design with more common standard nuts, with an extra feature added to achieve a specific functionality. Below are four of the shaped nuts most commonly used in construction and industrial applications.

Cap Nuts

Cap nuts are traditional hex nuts with the addition of a smooth dome on one side. These are used in assemblies where protection of the bolt or threaded is important after assembly, either for performance or for safety. Cap nuts can also be used for purely aesthetic reasons, such as in automotive uses or in residential construction, where the end of a bolt could cause an unsightly distraction for the user.

Acorn Nuts

Acorn nuts are a type of cap nut, where the domed side is pointed with a higher crown. This creates greater internal depth, allowing the bolt or rod to be threaded further into the nut.

Square Nuts

As opposed to the traditional hex (hexagonal) nut with its six sides, square nuts only have four sides and look exactly as they sound, a perfect square. Square nuts are typically used where there is an inset or channel in the receiving surface, such as in furniture, railroad applications, or other metal assemblies. The larger surface area of square nuts allows them to more easily resist loosening.

Wing Nuts

Wing nuts feature a head with two “wings” across from each other, making the nut able to be tightened and loosened by hand. Sometimes referred to as a “butterfly nut”, these are mostly used for the purpose of temporary fastening, but can also be found in bicycles and musical instruments.

If you have further questions about shaped nuts, please don’t hesitate to contact us for more information.

In our next edition of Know Your Nuts, we’ll be looking at the two most common types of nuts for wood. These nuts are used in applications where a durable thread is needed but the substrate is too soft for repeated assembly and disassembly. A common commercial use for these products is in the ready-to-assemble furniture industry, where products are shipped flat and need to be assembled by the consumer.

Tee Nuts

Tee nuts feature a thin, long body with a T-shaped flange at one end. The flange, which has 3 or 4 prongs attached to it, digs into the substrate to be flush with the surface, leaving it completely flat. Tee nuts are often used to fasten particle board, composite materials or wood more securely.

Insert Nuts

Insert nuts, sometimes called hex drive inserts, create a threaded socket for a wooden substrate, functioning much like a wall anchor. After a hole is pre-drilled, insert nuts are put into the hole, either by screwing or hammering it in. No matter how the nut is inserted, the external, teeth-like protrusions bite into the wooden substrate, which prevents the nut both from turning and from pulling out.

If you have further questions about nuts or inserts for wooden assemblies, please don’t hesitate to contact us for more information.

For our third edition of Know Your Nuts, we’re going to review the two most common types of structural nuts. The category of “structural nuts” includes heavy hex nuts that meet ASTM A194 GR. 2H, ASTM A563 GR. C, and ASTM A563 GR. DH specifications.

Grade 2H Nuts

Grade 2H nuts are a type of heavy hex nuts that distribute loads over a larger area, due to their size being about ten percent taller and ten percent wider and taller than standard hex nuts. Because Grade 2H nuts are similar in strength to Grade 9 bolts - roughly 20% stronger than typical steel nuts - uses in heavy machinery are quite common, such as assemblies in earth-moving equipment.

Grade DH Nuts

Grade DH nuts are heavy hex nuts made from medium carbon steel that have been heat treated. Designed and recommended to secure F3125 A490 structural bolts in assemblies, these nuts are often marked by the letters “DH”, although they are not required to be marked unless specified by the purchaser.

If you have further questions about structural nuts, please don’t hesitate to contact us for more information.

In our next edition of Know Your Nuts, we’re going to review the different types of all metal lock nuts. Designed to develop a “prevailing torque” between the bolt threads and nuts threads, all metal lock nuts increase the resistance to rotation in an assembly. Unlike nylon insert lock nuts, these nuts are effective in higher temperature environments (withstanding temperatures up to 1,400 °F ), since they’re completely made of metal. Below is a summary of the most common all metal lock nuts available.

Flange Nuts

Flange nuts feature a wide flange at one end that acts like an integrated washer, distributing the torquing pressure placed the nut across the surface of the material it’s being secured to. Often including serrations on the underside of the flange, these nuts are regularly used in assembly lines where the speed of using a single fastener, as opposed to separate nuts and washers, can help increase productivity and overall output.

Keps Nuts

Keps nuts are similar looking to standard hex nuts, but also include an attached, free-spinning washer. The washer is sometimes called a k-lock or star washer. A trademark of ITW Shakeproof, the name Keps is a reference to the “kep” in ShaKEProof, with an “s” typically added because more than one is purchased at a time.

Stover Lock Nuts

Stover lock nuts are single-piece, prevailing torque hex nuts that feature a conical top, flat bottom bearing surface, and chamfered corners. In Stover lock nuts, the locking action is created by distortion of their top threads during torquing, and can withstand severe shock loads and vibration.

Two-Way Reversible Lock Nuts

In a two-way reversible lock nut, a standard hex nut is compressed with two or three indentations on the flat sides of the nut. These compressions can be circular or rectangular, but must be equal distances from each other. In order to create a controlled locking mechanism, the compressions slightly distort the center threads that lock when engaged with the mating bolt or screw. Designed for use with machine screws and low-carbon bolts, the two-way reversible lock nut allows for automatic assembly.

If you have further questions about all metal lock nuts, please don’t hesitate to contact us for more information.

In the first installment of our Everything but the Bolt educational series, we’re taking a look at all different types of nuts. While many applications only need a very basic nut, we’ll review the different types of nuts (both standard and specialty), and give you the information you need to make a decision about which nut is best for your application.

We’ll start with the most quintessential version of a nut on the market - common hex nuts. Below is a description of the different types of common hex nuts available.

Finished Hex Nuts

A finished hex nut is the most basic of nuts - the six-sided nut that almost everyone first pictures in their mind when they hear the word “nut” in an industrial context.  Hex is short for hexagon, referencing the six sides of the nut. These nuts feature internal threading and are commonly used with machine thread bolts and screws, in applications where no “locking” mechanism is required.

Hex Jam Nuts

Hex jam nuts are low profile - usually only about half as thick as a standard hex nut. Commonly used as a type of lock nut, the jam nut is "jammed" against a standard nut to lock the two in place. Jam nuts are also sometimes used in applications where a traditional, larger profile hex nut would not fit.

Machine Screw Nuts

Designed specifically to be used with machine screws, these hex nuts are much smaller sizes than full-size hex nuts and feature flat tops and chamfered corners. Threads can be coarse (UNC) or fine (UNF), and zinc plating is the most common type of finish applied to machine screw nuts.

Nylon Insert Lock Nuts

Nylon insert lock nuts are very similar to basic finished hex nuts, but feature a nylon insert lock to help secure the nut into place. When a nylon insert lock nut is installed onto a bolt or screw, the nylon insert wraps around the threads, protecting the connection from loosening due to vibration.

If you have further questions about common hex nuts, please don’t hesitate to contact us for more information.

Have you ever looked at the head of a bolt and wondered what the markings mean? Maybe there's a series of letters and numbers, maybe just a few lines.

The markings on the heads of bolts serve two different purposes:

1. The markings can indicate who manufactured the bolt. This will vary from manufacturer to manufacturer, but is usually one, two or three characters.

2. The markings can identify the standard to which the bolt was made. For instance, if a bolt head contains three radial lines, then it's a Grade 5 bolt. If it contains five radial lines, then the bolt is Grade 8. If the bolt is manufactured to a particular grade based on standards set by the American Society for Testing and Materials (ASTM), then the marking will show a combination of letters and numbers.

Mudge Fasteners wants to help you decipher these head markings and when you'll need to know them. Download our bolt head markings chart to reference any time you need to figure out the grade of a bolt you're using or looking for. If you still have questions not addressed in the chart, don't hesitate to contact us for help.

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Do you know what the differences between American Standard (imperial) fasteners and metric fasteners are? If you’re choosing fasteners for a particular application, it will be important to know these differences.

Sometimes, the choice between using imperial fasteners or metric fasteners are just a matter of preference. Other times, it may depend on the market you're selling your end product to - if your target market is using metric fasteners regularly, it would be wise to stick with metric fasteners. This is why some manufacturers who are based in the United States where imperial fasteners are standard, but sell more volume in Europe where metric fasteners are standard, choose to use metric fasteners in their products.

If you need to use a wide variety of sizes within a relatively small range for your application, then metric fasteners may be a better choice, since they scale in size more easily than standard fasteners. Also easier is the process of subdividing units of measurement in the metric system.

We created a chart to help you sort through the differences in materials, mechanical properties, markings, thread sizes, tensile strengths and more.

If you still have questions about the differences between metric and imperial fasteners not addressed in this chart, just contact us, we’ll be happy to help.

The primary activities of standards organizations, bodies, standards developing organization (SDO) or standards setting organization (SSO) are developing, coordinating and producing technical standards that address the needs of a relatively wide base user base. Many of these organizations affect the fastener industry, and depending on which parts you’re dealing with, one or more of the organizations listed below may be involved.

ASTM International: American Society for Testing and Materials
ASTM International is the leader in development of international standards around the globe. At least 12,000 ASTM standards that are currently in use throughout the world, improving product quality and enhancing safety of the products bearing the ASTM seal.

SAE International: Society of Automotive Engineers
Based in the United States, the Society of Automotive Engineers (SAE) is global consortium of 138,000+ engineers and technical experts. These experts use their collective knowledge to primary focus on aerospace, consumer automotive and commercial vehicles. The SAE is committed to life-long learning and developing standards via voluntary consensus.

AISI: American Iron and Steel Institute
North American steel producers formed the American Iron and Steel Institute (AISI) over a century ago, earning it the title of the oldest trade association in the United States. AISI advocates for policies supportive of domestic manufacturing that also provide high-quality products to a wide range of customers, with the goal increasing the market for North American steel in both traditional and innovative markets.

ANSI: American National Standards Institute
The American National Standards Institute (ANSI) is best known as the voice of the United States standards and conformity assessment. ANSI oversees creation, promulgation and use of thousands of guidelines that impact nearly every sector of business, with topics ranging from construction equipment to acoustical devices, and from energy distribution to dairy and livestock production. ANSI also offers accreditation programs to assess management systems and conformance standards.

ASME: American Society of Mechanical Engineers
The American Society of Mechanical Engineers (ASME) provides manufacturers with standards for guidelines and tolerances for bolt conformity.  Some types of bolts, like the hex cap screws used in automotive applications, require very narrow tolerances, while construction grade fasteners have more broad tolerances. All of the tolerances are laid out by the ASME specifications are crucial in the manufacturing process.

IFI: Industrial Fasteners Institute
Established in 1931, the Industrial Fasteners Institute (IFI) is a standards organization and publisher based in Ohio, whose primary focus is representing North American mechanical fastener manufacturers. IFI standards are regularly used as a guide to design by machinists, mechanical engineers and manufacturers of bolts, nuts, machine screws and other engineered fasteners.

When it comes to fasteners, IFI does not create standards, but rather manages standards, creating technical information and handbooks to represent, support and protect fastener manufacturers.

ICC: International Code Council
The International Code Council (ICC) is a member-focused association, dedicated to the development of model codes and standards. These codes and standards are used during the design, build and compliance processes of construction, with the goal of creating safe, affordable, sustainable and resilient buildings. Most commodities in the United States, as well as many global markets for commodities, implement ICC code compliance for regulation.

UL: United Laboratories
United Laboratories (UL) aims to advance the building products industry’s goal of achieving safety and innovation. To do this, UL provides cost-effective, reliable product testing and certification with flexible, customized service options.

ISO: International Organization of Standards
The International Organization of Standards (ISO) is an independent, international, non-governmental organization that brings together experts to share knowledge and develop voluntary, consensus-based, market relevant International Standards. With a membership of 161 national standards bodies, ISO supports innovation to provide solutions to global challenges.

DIN: German Institute for Standardization
The German Institute for Standardization (DIN) creates standards that have been developed at the national, European and international level. With DIN, anyone can submit a proposal for a new standard, and if accepted, DIN carries out the standards project according to procedures authored by relevant Standards Committees. When it comes to fasteners, DIN standards are typically only for parts manufactured in metric sizes.

JIS: Japanese Industrial Standards
The Japanese Industrial Standards (JIS) organization is the primary body specifying standards for industrial activity in Japan. The JIS standardization process is coordinated by their Standards Committee and published through the Japanese Standards Association. The most common place JIS standards show up in the fastener industry are in relation to the automotive field.

COLA / LARR: Los Angeles Research Report
While not exactly a standards organization, here in Los Angeles the Department of Building and Safety reviews and approves the use of building, electrical, mechanical products within the City of Los Angeles. If a product is approved by LADBS, a letter is issued that contains a Los Angeles Research Report (LARR) Number, which require renewal every two years. During plan check, an engineer may ask for the LARR numbers of products used to be clearly identified. Fasteners, especially innovative, branded fasteners like those from Elco and DeWALT, are the most common products in construction to require an LARR.

RCSC: Research Council on Structural Connections
The Research Council on Structural Connections (RCSC) is a non-profit volunteer organization. RSCS is comprised of more than 85 experts in the fields of design, engineering, fabrication, erection and bolting of structural steel connections. Research projects funded by the RCSC seek to provide reliability, safety and standard practices for the international steel construction industry.

MS: Military Standard
This United States defense standard is used to help achieve standardization objectives by the U.S. Department of Defense. Often informally called mil-spec, this standardization helps achieve interoperability, ensuring fasteners meet certain requirements of reliability, total cost of ownership, commonality, logistics systems compatibility, and other similar defense-related objectives.

AN: Air Force-Navy Aeronautical
Like MS, AN is applied to fasteners and other parts that meet a specified standard put forth by the Air Force and Navy, generally regarding items used in aeronautical manufacturing. In some cases, MS and AN parts share the same item numbers, but that is not always. If you have any questions about which fasteners meet either MS or AN standards, please contact us.

NAS: National Aero Space
Developed by the aerospace industry, the National Aerospace Standards (NAS) are voluntary standards created by experts on certain subject matters from member companies, who participate in committees and working groups. The library of NAS standards, which contains more than 1,400 documents, cover a wide variety topics including bolts, rivets, washers, screws, nut plates, pins, knobs and more.

If you need help finding parts to meet any of these standards, please contacts us.

A bolt’s size is classified based on a number of dimensions, namely the bolt’s diameter, length of shank, thread pitch, grade, thread length and head size. Bolts can me specified in metric using millimeters, but the standard, internationally-recognized descriptions of bolt sizes are in inches.

If you’re looking to figure out the size of a bolt needed in an assembly and have a bolt that has worked on hand, follow the steps below to identify the dimensions of the bolt:

Step 1: Measure the shank’s diameter

The shaft of the bolt is called the shank, and its diameter is the first dimension used to describe a bolt size. This can be done using calipers or a bolt gauge.

Step 2: Determine the thread pitch

Thread pitch is a designation related to the number of threads per inch on the bolt’s shank. You can complete this measurement by simply counting the number of threads in an inch worth of shank. If the shank is less than one inch, you’ll need to multiply the number of threads to reach a full inch worth of threading.

Step 3: Measure the length of the shank

This is the measurement from where the shank meets the head to the very tip of the fastener.

Step 4: Determine the bolt’s grade

The grade of a bolt is determined by the type of metal used in the manufacturing of the bolt, as indicated by the bolt’s head markings. No one expects you to know all of the head markings by heart, just use our handy bolt head marking chart to make the determination.

Step 5: Determine the shape of the bolt’s head

This should be a simple one. While the most common bolt head is hex (six-sided), some applications require a four-sided square head or the dome-shaped head of a carriage bolt.

Step 6: Measure the length of the threaded portion of the bolt

As opposed to the shank length measured in Step 3, this measurement should specify only the length of the threaded portion of the bolt. One instance in which this would be useful to know is when determining whether you need a standard hex bolt or rather a fully threaded tap bolt.

Still having trouble determining how to measure a bolt for your application? Don’t worry, contact us and we’ll be happy to walk you through it.

Bolts are one of the most used fastener types in the world, finding usefulness in widely varied industries, from construction to automotive, manufacturing to renewable energy. By definition, a bolt is a fastener made up of a head at one end, a threaded shaft in the middle, and a chamfer (slightly bevelled edge which helps with inserting the bolt into nuts) at the other end.

While the terms “bolt” and “screw” are often used interchangeably, the primary difference between the two in general terms is that a bolt passes through a substrate and is captured on the other side by a nut, while a screw threads directly into the substrate.

Here are the most commonly used types of bolts and how they’re used:

Anchor bolt
Anchor bolts, or “anchors” for short, are generally used in concrete or masonry for structural applications. There are many specialized anchors that can be used in cracked concrete per ICC code approvals.

Carriage bolt
Carriage bolts are generally used to attach metal to wood, and feature a square undercut to the head, helping hold the bolt in place after tightening.

Hex bolts

Flange bolt
Flange bolts, sometimes known as frame bolts, are able to distribute the bearing load by utilizing a washer attached to the underside of the head.

Hanger bolt
Hanger bolts are threaded at both ends, with one tip featuring a wood screw point. Hanger bolts are often used in solar racking installation.

Hex bolt / Tap bolt
A hexagon bolt, almost always referred to as just a “hex bolt”, is what most people envision when the word “bolt” is evoked. With a six-sided head, the bolts feature threading for a portion of the shank. When the threading fills the entire length of the shank in a hex bolt, it is then known as a tap bolt.

Lag bolts

Lag bolt
Commonly and maybe more appropriately called lag screws, lag bolts create their own mating thread in wood and other materials when tightened.

Sex bolt
Instead of mating with a nut, sex bolts have a threaded shank that are then inserted into a mating female component. When the fastening components of an assembly cannot be exposed to abrasive threads, sex bolts are the part to use.

Square head bolt
A square head bolt is exactly what it sounds like it is… essentially a hex bolt but with a four-sided head instead of a six-sided head.

Stud bolt
Stud bolts feature hexagon nuts on both ends and operate by fastening components of the assembly between the two bolts.

U-bolts

T-head bolt
T-head bolts, also know as “hammerhead bolts”, feature T-shaped head that is usually inserted into a slot. These types of bolts are often used when insertion into the slot presents an opportunity to lock the bolt into place upon tightening, such as in concrete embed channels.

Toggle bolt
Toggle bolts feature expanding nuts and are used to mount objects to walls where the side of bolt opposite the head cannot be reached once inserted.

U-bolt
U-bolts are shaped similar to staples, featuring a bent design that creates a “U” with partial threading on both ends.

Still not sure which bolt type is best for your application? Contact Mudge Fasteners and let one of our fastener experts help you decide.

Bolts can be either ferrous or non-ferrous, meaning that they either contain iron (ferrous) or don’t contain iron (non-ferrous). So what’s the difference between the two, and what are the characteristics of each?

Obviously, the biggest difference is that ferrous bolts contain iron, while non-ferrous bolts do not. Ferrous metals are magnetic, and are also more vulnerable to corrosion and rust in outdoor environments. Non-ferrous metals tend to be significantly lighter that ferrous metals, which can be seen in the weight difference between materials like aluminum, copper and brass (non-ferrous) versus carbon steel (ferrous).

Ferrous metals, and the bolts made from them, are traditionally stronger and less expensive than their non-ferrous counterparts. Non-ferrous metals, and the bolts made from them, have a lower density, are non-magnetic, and are colorful or able to be made colorful.

Some examples of ferrous metals include non-alloy steels, stainless steel, low, medium and high carbon steel, and some alloy steels, such as chromium and nickel. Examples of non-ferrous metals include copper, aluminum and zinc.

All these factors affect what bolts you should choose for your application. Looking for super-durable, low-cost bolts? Maybe carbon steel bolts would be best for you. In need of something very light and corrosion-resistant? Then look for a bolt in the non-ferrous material family.

If you still have questions about ferrous versus non-ferrous bolts, Mudge is here to help. Contact us for more information from one of our knowledgeable fastener experts.

Carbon steel anchors (ferrous)

Purple aluminum hex cap screws (non-ferrous)

When selecting metals to be joined, especially when selecting what material a fastener in your application should be, galvanic series relationships are a useful guide. This information will help you determine which metals will have a minimal tendency to interact galvanically with each other... i.e. cause galvanic corrosion.

When looking at the galvanic series chart, the further away two metals are from each other, the higher the risk of galvanic corrosion, which can and should be prevented during the design phase.

If you need help selecting the correct fastener material for your application, contact us and we’ll be happy to give you the answers you need.