Answer: Both ASTM A194 Grade 2H nuts and ASTM A563 grade DH nuts are high strength nuts that undergo a heat treating process required to develop their strength characteristics. However, they are not necessarily interchangeable.

An A194 Grade 2H nut can always be substituted for an A563 Grade DH nut. In fact, the ASTM A563 nut specification specifically states that substituting an A194 Grade 2H is acceptable.

ASTM A563 – Table 3 – Note D states:

“Nuts made in accordance with the requirements of Specification A194/A194M, Grade 2H, and marked with its grade symbol are an acceptable equivalent for Grade DH nuts. When A194 zinc-coated inch series nuts are supplied, the zinc coating, overtapping, lubrication and rotational capacity testing shall be in accordance with Specification A563.”

Due to availability and/or cost issues, ASTM A194 Grade 2H nuts may be preferable to an ASTM A563 Grade DH nut. It is not uncommon for A563 Grade DH nuts to be completely unavailable in some diameters and finishes. The reverse is also true for A194 Grade 2H nuts, which can be unavailable or impractical from a cost perspective in certain diameters and finishes. Does this mean a supplier should substitute A563 Grade DH nuts for A194 Grade 2H nuts?

The answer is no. An ASTM A563 grade DH nut may be substituted for an ASTM A194 grade 2H nut under most, but not all, circumstances. A194 Grade 2H nuts undergo additional heat treating and testing processes that A563 Grade DH are not subjected to. This additional processing and testing allows A194 Grade 2H nuts to be used in high temperature applications. In particular, ASTM A193 Grade B7 (a high temperature bolt specification) specifically requires the use of A194 nuts. A563 Grade DH nuts are not an acceptable substitution for this bolt specification.

Both ASTM A563 Grade DH nuts and ASTM A194 Grade 2H nuts are compatible with the following ASTM bolt specifications:

• A307 Grades A and B
• A449 Type 1
• A325 Type 1
• A354 Grades BC and BD
• A490 Type 1
• F1554 Grade 36, 55, and 105

The compatibility of nuts for various grades of bolts can be verified with our Nut Compatibility Chart.

Below is a transcript of a recent live chat that we had on our website addressing shear strength. The chat was fielded by our very own Dane McKinnon and serves as a good example of what kind of response you can expect when you ask us a question. We’re substituting a generic name below for the customer to protect their privacy.

• Visitor: Henry
• Operator: Dane McKinnon
• Company: Portland Bolt
• Started: 26 Jan 2010 12:07:57
• Visitor: 26 Jan 2010 12:22:18

Henry:
What is the shear strength of grade 8 bolts 1/4″ – 1″

Call accepted by Dane McKinnon. Currently in room: Dane McKinnon, Henry.

Dane McKinnon:
Good afternoon Henry. Shear strength is typically 60% of tensile strength, and the minimum tensile strength of a grade 8 bolt is 150,000 psi. We have an FAQ that addresses this question here: http://www.portlandbolt.com/faqs/bolt-shear-strength-considerations

Henry:
How are all grade 8 bolts the same tensile strength?

Dane McKinnon:
They are all the same tensile strength per square inch. The larger ones have a larger cross section of material, and so are therefore stronger. To calculate the tensile strength of a particular size, you would multiply 150,000 psi by the tensile stress area, found here: http://www.portlandbolt.com/technicalinformation/thread-pitch.html

Henry:
Thank you

Henry is now off-line and may not reply. Currently in room: Dane McKinnon.

Dane McKinnon has left the conversation. Currently in room: room is empty.

Have a bolt related question of your own? Try our live chat feature and get the answer you need quickly.

Answer: Absolutely not! Externally threaded fasteners should never be “chased”. During the hot-dip galvanizing process, excess zinc has a tendency to build up in the threaded portion of a fastener. Chasing threads is a term used to describe re-cutting threads after galvanizing to remove this excess zinc gained during the galvanizing process. Chasing threads will not only remove the excess zinc, but often removes much, if not all of the zinc coating and eliminates the corrosion protection on the threaded portion of the fastener. Chasing, if not performed with extreme precision, can also remove additional steel from the threaded portion of the fastener resulting in threads that are undersized and out of tolerance.

One misconception with regard to galvanized threads is that the threads are cut undersized to accommodate for the extra 2-6 mils of thickness that hot-dip galvanizing adds. Actually, bolts are threaded the same regardless of whether or not they will be galvanized. It is the galvanized nuts that are tapped oversize to ensure a proper fit. When galvanized bolts are chased and some or all of the zinc is removed from the threaded area, the galvanized nuts which are tapped oversize will be too loose and not generate the proper clamping force required of the connection. The tolerance for tapping galvanized nuts is covered under A563.

ASTM F2329 is a relatively new specification that covers galvanized fasteners and supersedes A153. This specification (5.4.1) clearly prohibits the alterations of threads after galvanizing stating, “Fasteners that have been hot-dip galvanized shall not be further altered (such as subjected to a cutting, rolling, finishing-tool operation) by the galvanizer unless specifically authorized in writing…”

Portland Bolt’s custom galvanizing system is specifically designed for threaded fasteners and uses centrifugal force to clean the threads. After parts are removed from the molten zinc they are immediately spun using a high-speed centrifuge to remove the excess zinc. This process creates high quality galvanized threads and a trouble-free nut fit. Although some galvanizing companies do a good job of processing fasteners, the reality is that many other galvanizing companies simply do not have the specialized equipment and systems to properly galvanize fasteners. For galvanizing companies, fasteners are a hassle. Galvanizers charge their customers a price per pound and profitability for them is driven by the amount of weight they can put through their system per hour. Galvanizing companies prefer to galvanize large structures like beams, plates, and poles that are heavy, in and out of the tank quickly, and don’t require the high degree of quality control that threaded fasteners require. For this reason, many fastener manufacturers will be forced to “chase” the threads of fasteners after they have been hot-dip galvanized.

Ensure you are receiving galvanized bolts in which the threads have not been chased by questioning your supplier as to the methods used to clean the threads. Any form or re-cutting of the threads after they have been galvanized is simply unacceptable.

Answer: Most grade 8 bolts require a permanent marking symbol that is designated by 6 radial lines. However, the SAE J429 specification that covers grade 8 fasteners does not require grade markings for studs (fully threaded rods) or slotted and cross recess head products. Therefore, you will not be able to visually identify a threaded stud that is certified to an SAE specification.

On the other hand, ASTM specifications require studs to be marked on one end with a grade symbol and manufacturer’s identification. Our Fastener Identification Markings chart will help to identify various SAE and ASTM grade markings. For more information, see our FAQ on the differences between SAE and ASTM graded fasteners.

Why do fastener salespeople try to substitute products?

Before we explore why these and other types of substitutions are often unacceptable, let’s take a step back and figure out why salespeople are so anxious to substitute one product for another. Whether you’re selling bolts, shoes, or cars, any Sales 101 course teaches that if you don’t have exactly what the customer is looking for, substitute something else before that customer has a chance to buy what they really want from your competitor. Trying to sell a customer a pair of Nike running shoes instead of the Adidas they preferred because you were out of stock in their size has no potential liability issue attached. Salespeople, especially commissioned ones, simply want to close the sale regardless of whether or not you end up with what you need. However, shoes don’t hold up bridges, support high-rise buildings, or secure light poles to their foundations. Allowing a salesman to substitute a different grade or configuration of fastener that an engineer has specified, could have catastrophic implications.

Most fastener companies do not employ engineers.

Most fastener companies, whether they are a manufacturer like Portland Bolt or a distributor who simply buys and resells standard fasteners, do not employ structural engineers who are qualified to recommend substituting anything other than the exact grade and configuration of product that was originally specified. Engineers identify a specific grade of fastener for a connection based on a variety of factors that include strength, ductility, configuration, thread pitch, corrosion resistance, etc.

Limited or no manufacturing capabilities.

To further understand why bolt salespeople attempt to sell you a different grade or configuration of product than you actually need requires a deeper understanding of the types of companies that comprise the fastener industry. Let’s start with bolt manufacturers. Portland Bolt is a manufacturer of nonstandard anchor bolts and construction fasteners. Our manufacturing capabilities are extremely broad and encompass headed bolts through 2-1/2″ diameter, bent bolts through 4-1/2″ diameter, and threaded rods through 6″ diameter. We inventory just under one million pounds of round bar that will allow us to manufacture to virtually any ASTM bolt specification. On the other end of the spectrum are fastener distributors. These companies buy and resell mass produced and imported fasteners in addition to wrenches, ladders, tools, hard hats, and other construction related equipment. They have no manufacturing capabilities whatsoever. Somewhere in the middle of manufacturers and distributors lie hybrid companies who are primarily distributors, but also have limited manufacturing capabilities. Perhaps they thread mild steel round bar, but don’t have the ability to forge headed bolts or thread high strength round bar. If you don’t know the manufacturing capabilities of your primary fastener supplier you should ask.

With a better understanding of the industry it is easy to see that companies who do not have access to specific grades of steel or who do not have the ability to manufacture specific types of fasteners will undoubtedly attempt to pass off a different grade or style of fastener that they claim is “equal or better” than the grade or type of fastener that has been specified on your project. In this economy, desperation to consummate a sale may result in a salesperson attempting to substitute just about anything. If you take their word as gospel, you could be exposing your company to a tremendous amount of liability. Do you really want to gamble that a person who has been selling fasteners for six months really knows if the bolt they are passing off as an acceptable substitute really is? Knowingly supplying incorrect product can have devastating legal implications.

Product liability insurance……what’s that?

Ever asked your primary bolt supplier how much product liability insurance they carry? What if they suggest a substitution that gets rejected…worse yet…..after installation? What now? Well they will certainly step up and replace the product, pay for the cost of labor to remove and reinstall the correct fasteners that should have been supplied in the first place, and cover any back charges….won’t they? Don’t be so sure. Next time you talk with them you might find out if they carry enough insurance to fix their mistake. You might discover you’ll be on your own.

Common misconceptions.

Let’s look at the two most common misconceptions in the fastener industry.

Misconception #1 – Stronger is always better.

In the fastener industry, stronger is NOT always better. An engineer may have wanted a certain combination of strength and ductility that a particular fastener specification offers. Substituting a stronger fastener results in a reduction in ductility which could have disastrous results.
In the opening of this FAQ, we used an example of the common practice of substituting A193 grade B7 for F1554 grade 55 anchor rods (or just about any other ASTM specification for that matter). A193 grade B7 all thread rod is a high strength material that will exceed the strength of many other ASTM specifications. The tantalizing thing about B7 rod is that virtually every fastener company in the country stocks it. It is a quick fix for just about any situation due to its relatively low cost and immediate availability. However, B7 doesn’t meet the requirements of F1554 grade 55 due to the fact that F1554 grade 55 has a maximum tensile strength requirement of 95ksi that A193 grade B7 will always exceed (125 ksi minimum). In essence, B7 is too strong to meet the requirements of F1554 grade 55. There is a good chance that the engineer specifying the fasteners wanted the combination of strength, ductility, and possibility weldability that F1554 grade 55 provides.

Misconception #2 – Threaded rod with a nut tack welded can be substituted for headed bolts.

First, only mild steel rods should be welded. AISC recommends against welding high strength materials. Applying heat during a welding operation could alter the mechanical properties of high strength steel. Second, Portland Bolt’s in-house testing of certain rods with nuts in lieu of forged heads found a significant reduction in strength.

Summary

If you are a purchasing agent, project manager, superintendent, or in any other role that empowers you to procure fasteners for your company, you have a tremendous responsibility to your organization to purchase the exact product that has been specified on your project. If you allow a fastener company to sell you an alternate product they claim will be an acceptable substitute, it is your responsibility to make sure that product will work for your application. If you don’t, you may be opening a can of worms.

Answer: No, SAE only covers bolts up to and including 1½” diameter. SAE J429 (1999), the specification that includes Grade 2, 5, and 8 fasteners, states, “This SAE standard covers the mechanical and material requirements for inch-series steel bolts, screws, studs, SEMS, and U-bolts used for automotive and related industries in sizes to 1½ in. inclusive.”

When diameters larger than 1½” are required, ASTM specifications should be considered since many cover fasteners larger than 1½” diameter. Generally speaking, for construction applications ASTM is the most appropriate standard. SAE is more commonly specified for automotive, equipment, or machinery applications.

We often see fastener distributors and manufacturers without forging capabilities talking customers into switching from a headed bolt to a rod with a nut since they are unable to provide the forged product that was engineered into the structure. Substituting a nut for a forged head is not limited to anchor bolts, but that is where we see it occur most frequently. Making the decision to switch from a bolt with a forged head to a rod with a nut should always be approved by an engineer to prevent any liability in making such a substitution should a failure of the fasteners occur.

Wedge Testing per ASTM F606

Headed Anchor Bolts

Rod with a Nut

Note: Wedge testing as shown above is required to obtain mechanical properties for most ASTM high strength fasteners. A greater difference was found for high strength fasteners than mild steel fasteners during Portland Bolt in-house testing of headed bolts versus rods with a nut. The reduced cross sectional area at the junction of the nut as compared to a bolt with a forged head caused the fasteners with a nut acting as a bolt head to break at lower strengths than the bolts with forged heads. Additionally, the high strength rods with a nut acting as a head broke just below the nut which would automatically constitute a failure since the wedge test requires the bolt to break either in the body of the bolt or in the threaded portion, not at the junction of the head.

Answer: According to the American Galvanizers Association (AGA) the weight of an item on average will increase about 3.5% from the zinc added during the galvanizing process. However, the AGA goes on to say, “…that figure can vary greatly based on numerous factors. The fabrication’s shape, size, and steel chemistry all play a major role, and other factors like the black weight, the different types of steel that get welded together, and the galvanizing bath chemistry can also have an effect.”

When considering galvanized fasteners this percentage is often lower. For example, the actual increase in the weight of a galvanized 1″ x 10″ A307 hex bolt compared to a plain hex bolt is approximately 0.26%. The zinc thickness requirement for hot-dip galvanizing threaded fasteners is covered by ASTM F2329. This specification states the average minimum coating thickness at 1.7 mils (.0017 in.). Overall the weight increase of fasteners due to zinc from galvanizing is fairly minimal.

Protective Coatings
ASTM recommends that if a protective coating is required for A490 bolts a Zinc/Aluminum Corrosion Protective Coating should be used in accordance with F 1136 Grade 3. This recommendation is based on findings from research conducted by the Industrial Fastener Institute (IFI 144). No other metallic coating is allowed unless authorized by ASTM’s fastener Committee F16. One trade name of this coating is Dacromet.

Weathering Steel
Another option is to specify ASTM A490 Type 3. This fastener is made from weathering steel which is inherently corrosion resistant. However, these fasteners are not as readily available in the marketplace as A490 Type 1.

Consulting a structural engineer involved on the project is always the best solution.

Answer: There are two specifying bodies when it comes to fasteners. ASTM (American Society for Testing and Materials) covers primarily bolts and fasteners for construction applications. SAE (Society of Automotive Engineers) covers fasteners for automotive, machinery, and OEM applications.

ASTM A307 grade B is made from a low carbon steel and is a relatively low strength heavy hex bolt or stud specifically intended for cast iron pipe flange connections. ASTM A449 is a medium carbon steel that is heat treated to develop higher strength characteristics than A307 grade B. Whereas A307 grade B is limited by its configuration (heavy hex head bolt or stud) and its application (cast iron flange connections), A449 can be used for general applications and is unlimited in its configuration. In other words, an A449 bolt can be any type of headed bolt, any shape of bent bolt, or straight rods that are fully threaded, have threads on both ends, or have tread on one end only. Grade 5 bolts are covered under SAE guidelines and by nature are a more precision fastener than ASTM bolts. They are virtually identical to ASTM A449 in chemistry and strength, but max out at 1-1/2″ diameter while A449 bolts extend to 3″ diameter.