Newest FAQs

Difference between F594 & A194 nuts

What is the difference between F594 and A194 nuts?

For this FAQ, we are focusing on the 304/316 alloys and their common, default strength conditions. Within both F594 and A194, there are many less common, exotic grades and multiple strength conditions. Exploring all possible permutations of all grades would be unnecessarily complicated. For more details, the actual ASTM standards can be purchased from ASTM,... Read more

Thread Class for All Thread Rod

Is all thread rod produced with a Class 2A thread?

There are three classes of thread fit associated with fasteners: Class 1A/1B, Class 2A/2B, Class 3A/3B. The “A” refers to the externally threaded fastener component, typically the bolt, while “B” refers to the internally threaded fastener component, usually a nut. As the number of thread class increases, the threading tolerances become more precise. Most construction... Read more

Heat-treatment After Forging

Do headed bolds receive heat treatment before or after the heads are forged?

Not all grades of bolts require heat-treating, but those specifications that do are heat-treated after the heads are forged. Heat-treating is performed in a controlled environment using specific quenching and tempering temperatures and durations. The bolts are then tested to ensure the strength of the heat-treated bolts meet the requirements of the given specification. Since... Read more

Shipping Quantities of +/- 10%

Why do some manufacturers have a policy of shipping quantities of +/- 10%?

Portland Bolt does not abide by the practice of shipping quantities of +/- 10%. We feel this policy is ludicrous. We ship exact quantities and the reason is explained below. Shipping +/- 10% is done as a cost-cutting measure by many manufacturers. Since several parts are lost during the manufacturing process (some are used for... Read more

A194 Grade 4 vs. Grade 7 Nuts

What is the difference between A194 Grade 4 and A194 Grade 7 heavy hex nuts?

While A194 Grade 4 and A194 Grade 7 nuts are mechanically identical and have the same intended applications, the only difference is the chemical values (aka steel used to manufacture). Grade 4 was created to be a low-cost alternative to Grade 7 by using a lower cost raw material. Unfortunately, this did not work out.... Read more

What is the meaning of UNO?

What is the meaning of UNO?

What is the meaning of UNO? UNO is an acronym that stands for, “Unless Noted Otherwise”. UNO is a blanket statement that covers all specified items related to the callout but leaves exceptions in specific situations. For instance, A325 bolts may be specified in the general notes, but a different fastener specification/grade may be specified... Read more

Measuring Round bend U-bolts

How does Portland Bolt measure round bend U-bolts?

Portland Bolt measures round bend U-bolts based on the dimensions outlined in the Industrial Fastener Institute Standard IFI-136. The length (L) is measured from end of bolt to inside of the bend, while the width (C) is measured between the legs. Some companies will show the length to the bottom or centerline of the bend... Read more

Can A490 bolts be galvanized?

Can A490 bolts be galvanized?

The ASTM F3125 Grade A490 specification does not allow either hot-dip galvanizing (per ASTM F2329) or mechanical galvanizing (per ASTM B695) due to the risk of hydrogen embrittlement. The only coating currently allowed on A490 bolts is a zinc aluminum coating meeting any of the following specifications: ASTM F1136, F2833, or F3019. ASTM Committee F16... Read more

Fine Thread Structural Bolts

Can A325 and A490 structural bolts be supplied with fine thread?

No. The specification calls out that those bolts must be Unified National Coarse thread and have class 2A tolerances. The F3125/F3125M specification reads: 4.2 Threads: 4.2.1 Uncoated bolt threads shall be as specified in Table 1. 4.2.2 Coated bolts shall have threads meeting Table 1 requirements before coating. TABLE 1 Thread Fit, ASME 120 ksi... Read more

Plain Finish Bolts

What is a "Black" Bolt?

The vast majority of bolts that Portland Bolt provides are either hot-dip galvanized or plain steel with no coating. In the construction fasteners industry, we typically refer to the plain steel as “black.” On our quotes and orders at Portland Bolt, we abbreviate that to “blk”. Other companies may refer to bolts with no coating... Read more