Answer:  The simple answer here is no.  ASTM A709 is a specification that covers carbon and high-strength structural steel plates and bars intended for use in bridge applications. There are multiple grades of A709 and Grade 36 covers the structural steel made from mild carbon steel, such as A36.  Although Portland Bolt would manufacture an A709 Grade 36 bolt out of the same material we would use for A307 Grade A bolts or F1554 Grade 36 anchor bolts (which are standard mild steel fastener specifications), ASTM A709 is not a fastener specification. This specification only covers structural steel used in bridge applications. It does not provide the manufacturer with the bolt guidelines which are necessary for the manufacturing process, such as bolt configuration, thread type/amount, compatible nuts/washers and so on. Without having these necessary details, the bolt would not be manufactured without a long discussion regarding every little detail between the manufacturer and the purchaser.

For more information on why bolts cannot be ordered to steel specifications, see the FAQ Ordering Bolts to ASTM A36.  It saves time and money for both parties if a proper bolt specification is called out.  To see a list of different bolt specification grades and their strength requirements, visit our Strength Requirements by Grade Chart. If you have further questions regarding this topic or similar topics, please give us a call.  We have 9 estimating bolt experts and we are happy to assist you with whatever fastener questions you may have.

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Answer: Unfortunately there appears to be no documented information on how much rod engagement into a coupling nut is required to achieve the strength of the rod or bolt being used with it.  Coupling nuts are manufactured to the same ASTM specifications as regular hex nuts, and ASME B18.2.2 provides dimensional specifications for coupling nuts.  Standard coupling nuts are 3 diameters in length.  However, there is no reference to coupling nuts in the actual ASTM A563 or A194 nut specifications.

Your first step is making sure that the ASTM grade of coupling nut being used with the threaded rod or bolt is the same grade as the recommended grade of nut that would be used with the rod or bolt.  For example, ASTM A193 B7 rods or bolts require an ASTM A194 2H Heavy Hex nut, so if you were to use a coupling nut with an ASTM A193 B7 rod, the grade of coupling nut should also be ASTM A194 2H.  Although the amount of thread engagement is not specified, our coupling nut supplier recommends the bolt or rod should be threaded a minimum of one diameter in length into one end of the coupling nut.

There may be an application which requires that the threaded parts going in each end of the coupling nut are engaged approximately one half of the coupling nut thickness.  In this case, a hole may be drilled in the middle of one side of the coupling nut.  This aids in the visual inspection to ensure that both rod ends are in fact meeting in the middle, not off center.  According to IFI-128, note 7,  the hole should be located at mid nut thickness and have a diameter of 0.2 to 0.4 times nominal nut size for sizes 2-1/2″ and smaller.  For sizes 2-3/4″ and larger, the hole is 1″.  Coupling nuts are manufactured without this hole unless otherwise specified.

As long as the correct grade of coupling nut is used and the bolts or rods are engaged a minimum of one diameter, the bolt should theoretically break before the threads strip.  Again, this is only a common rule of thumb and we have no documented specifications that cover this issue.  In any situation involving coupling nuts, we would recommend consulting with the engineer of record or a structural engineer to determine the appropriate length of coupling nut and amount of thread engagement required.

The post Coupling Nut Thread Engagement appeared first on Ask the Expert.

Answer: The answer can be found in AISC Design Guide 1,Section 2.11.3:

“Anchor rod projections that are too short or too long must be investigated to determine if the correct anchor rods were installed. If the anchor rod is too short, the anchor rod may be projecting below the foundation. If the rod projection is too long, the embedment may not be adequate to develop the required tensile strength.”

Too Low

If your anchor bolts are poured too low, the AISC offers five options.

1. Partially engage the nut
   

   “Often, when the anchor rod is short, it may be possible to partially engage the nut. A conservative estimate of the resulting nut strength can be made based on the percentage of threads engaged, as long as at least half of the threads in the nut are engaged. Welding the nut to the anchor rod is not a prequalified welded joint and is not recommended.”

2. Redrill and use an epoxy anchor
   

   “If the anchor rod is too short and the rods are used only for column erection, then the most expedient solution may be to cut or drill another hole in the base plate and install a drilled-in epoxy-type anchor rod.”

3. Extend using a coupling nut
   

   “When the rods are designed for tension, the repair may require extending the anchor rod by using a coupling nut…”

4. Butt weld extensions to the existing, already in place bolts if they are weldable anchors.
   

   “When the rods are designed for tension, the repair may require extending the anchor rod by (using a coupling nut) or welding on a piece of threaded rod. ASTM F1554 Grade 36 anchor rods and ASTM F1554 Grade 55 with supplement S1 anchor rods can be extended by welding on a threaded rod. Butt welding two round rods together requires special detailing that uses a run out tab in order to make a proper groove weld. The run out tab can be trimmed off after welding, if necessary, and the rod can even be ground flush if required.”

5. Extend the anchor by welding on splice bars to add on a threaded rod
   

   “It is also possible to extend an anchor by using splice bars to connect a threaded rod extension.”

Too High

If your anchor bolts are poured too high, the AISC only has one recommendation: use plate washers to make up the difference.

“When anchor rods are too long, it is easy to add plate washers to attain an adequate thread length to run the nut down to the base plate. As noted previously, anchor rod details should always include an extra 3 in. or more of thread beyond what the detail dimension requires to compensate for some variation in anchor rod projection.”

More detailed information and diagrams can be found in section 2.11.3 of AISC Design  Guide 1.  Your project engineer should also be consulted before any of these repairs are undertaken to make sure the best method for the specific application is chosen.

The post Anchor Bolts Installed Too Low or Too High appeared first on Ask the Expert.

Answer: This question is often brought to Portland Bolt’s attention by customers wondering how to install an anchor bolt sleeve with a 1-1/8” diameter rod.  This issue arises due to the fact that anchor bolt sleeves are not manufactured in 1-1/8” diameter. We knew of two different solutions, but were left wondering which was the preferred method of installation. In order to better answer this question, we contacted the anchor bolt sleeve manufacturers, Contec and Wilson, and obtained their expertise.

Installation Options

1. Buy a smaller diameter anchor bolt sleeve (in this case, a 1” diameter sleeve) and cut a larger hole into the plastic anchor bolt sleeve.
2. Buy a larger diameter anchor bolt sleeve (in this case, a 1-1/4” diameter sleeve) and use duct tape to fasten the anchor bolt sleeve to the anchor bolt.

Manufacturers’ Recommendation

“Both options are fine, but option number 1 (buying the smaller diameter and cutting a larger hole) is more labor intensive.  All the contractors we have dealt with opt to use the larger sleeve hole and duct tape.  It is faster and achieves the same results.” – Contec, Inc.

“The best option would be to buy the larger diameter anchor bolt sleeve and use duct tape to fasten it to the anchor rod.” – Wilson Anchor Sleeve LLC

It seems that the manufacturers are in agreement. When you need an anchor bolt sleeve to fit a diameter that is not manufactured, it is best to buy a larger sized anchor bolt sleeve and fasten it to the anchor bolt using duct tape.  This is the fastest method, which is often critical on a job site.  It is always the contractor and engineer on the job who have the ultimate say; make sure to consult with them to make sure all of the variables involved on your specific job are taken into consideration before making the final decision.

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Answer: In our Live Chat, numerous customers have asked us about tolerances under the F1554 specification relating to things like diameter, length, straightness, and many other parameters. While a customer always has the option of specifying a particular set of tolerances they may require for any bolt, what are the default tolerances for anchor bolts under the ASTM F1554 specification? Let’s take a look.

Section 10 of the specification covers dimensional tolerances.  Here is the breakdown for each dimensional tolerance that is given in the specification.

• Body Diameter (if rolled threads) – not less than the minimum pitch diameter.
• Body Diameter (if cut threads) – not less than the minimum major diameter.
• Bend Section (thickness of the steel in the area that is bent)- shall have a cross section not less than 90% of the area of straight portions.
• Length is measured from the underside of the head to the end of the threads for headed bolts or from the inside of the bend to the end of the threads for bent bolts.  It is broken down into two categories of length.
  1. For bolts 24” or shorter the length tolerance is  ± 1/2”.
  2. For bolts longer than 24” the length tolerance is  ± 1”.
• Hook length (short leg) –  ± 10% of the specified hook length, or  ± 1⁄2 in., whichever is greater.
• Bend Angle—The bend angle of hooks shall not vary from that specified by more than  ± 5°
• Thread Dimensions – Unless otherwise specified should be Unified Coarse Thread Series per ANSI/ASME B1.1 and have either Class 1A or 2A tolerances.
• Thread Length—+1.0 in./−0.00 in. from the length specified

This is the complete list of tolerances that are defined within the ASTM F1554 specification.  If a customer desires a tolerance beyond the stated values listed above, or, if they wish to have anchor bolts meet a tolerance that is undefined in the specification, the customer would need to explicitly define the values they are requiring to the manufacturer at the time of inquiry.

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Answer:  The answer to this question is no.  As stated in Section 1.1, the F1554 specification covers various configurations of, “…carbon, carbon boron, alloy, or high-strength alloy steel anchor bolts.”  In general terms, for a steel to be considered “stainless” it must contain at least 10.5% chromium as part of its chemical composition and will often have nickel or molybdenum as additional alloying elements.  The F1554 specification covers three different grades of material, Grade 36, Grade 55, and Grade 105.  As you can see in the chart below of the required chemical properties for each grade within the F1554 specification, there is no requirement for chromium (or nickel or molybdenum) in any of the grades covered by the specification.

Chemical Properties of ASTM F1554

(Above information taken from Section 8 – Tables 1 & 2 of the ASTM F1554 specification)

If anchors bolts need to be stainless steel then they should be specified under one of the ASTM specifications that cover stainless steel fasteners such as A193, A320, or F593.  More information on the differences between stainless steel bolts made under the aforementioned three specifications can be found here.

Portland Bolt can manufacture anchor bolts as straight rods, bent bolts, and headed bolts from both Type 304 and Type 316 stainless steel. If you would like a quote on stainless steel anchor bolts, you can submit a quote request through our website right now!

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Answer: Mechanical galvanizing (ASTM B695) is a process in which fasteners are tumbled in a barrel with a mixture of water, zinc powder, other chemicals, and glass impact beads. As the parts are tumbled in the slurry, the zinc is “cold welded” to the fasteners. While some mechanical galvanizers can process parts that over a foot long, and potentially up to a couple feet long, there are some difficulties processing long parts and especially any substantial quantity of long parts.

The process of mechanical galvanizing requires the parts to not only roll, but also tumble end over end thus acquiring the thickness and adhesion required by mechanical galvanizing specification. Larger parts do not tumble very well and thus are very difficult to coat. And when they do tumble, due to their long length and large weight, they can break the glass impact media used in the mechanical galvanizing process. The only effective way to mechanically galvanize parts over roughly 12” in length is to mix them with smaller product that will allow the process to be correctly performed and without damaging/hampering the process.

Some mechanical galvanizers will entertain longer parts, but only on a case-by-case basis and in limited quantities. For parts that number over 5 or 10 total quantity in a batch there would need to be special consideration by the mechanical galvanizer for the amount of product, length, and weight of each bolt. Large anchor bolts and construction fasteners that need corrosion protection over 12” long can be efficiently and successfully produced with a hot-dip galvanized finish that is more resilient and is actually bonded to the steel at a molecular level.

Portland Bolt performs hot-dip galvanizing within our 85,000 square foot manufacturing facility. Our in-house hot-dip galvanizing line is designed specifically for threaded fasteners. Hot-dip galvanizing is not restricted to the short length limitations that mechanical galvanized products are limited to. Contact us for your galvanized anchor bolt and nonstandard fastener requirements.

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Answer: Our two main concerns with providing galvanized bolts larger than 1-1/2” diameter with 8 threads per inch is the lack of overtap allowance standards for the mating nut and the potential for premature thread stripping due to the nut oversizing.

Overtap Allowances

All inch series hot dip galvanized hex nuts, regardless of grade, are tapped oversize to accommodate the extra 2 – 6 mils (.002 – .006) of zinc that is added to the threads of the bolt during the galvanizing process. Without this allowance, the nut would not thread onto the bolt. As you can see in the table below from ASTM A563, the diametral allowance increases with the size of the nut, maxing out at 0.050” overtap at 1-3/4” diameter and remaining the same up through 4”-4. You will also notice that the allowance for 8 TPI threads stops at 1-1/2” (0.027 for both UNC and 8-UN) and does not continue above it. The problem this causes is as follows: If you are manufacturing a 1-3/4”-8 UN nut, and are being asked to overtap it for hot dip galvanizing, how much do you overtap it? Do you assume that the pattern would continue and that the larger nut would need to be tapped 0.050” oversize, or is that too much for those finer pitch threads? That is an answer we don’t have, and that leads us into the second part of our problem, premature thread stripping.

Thread Oversizing Allowances

 Thread Stripping

An important fundamental of joint design is that, whenever possible, a joint should be designed so that the bolt’s breaking is the mode of failure, as opposed to the threads stripping, which can be a delayed and more catastrophic failure since it can go unnoticed until the joint is put into service. In calculating thread strength, the thread depth provides the resistance to stripping out, and that resistance must be greater than the tensile strength of the bolt or else the connection is unsafe. Two factors make large 8 TPI hot-dip galvanized fasteners less resistant to thread stripping. First, 8 TPI threads in large diameters have a shallower thread profile that of Unified National Coarse threads. A shallower profile means less thread depth, and thread depth is one of the major factors in stripping resistance. Second, when you oversize the internal threads of the nut (without any specific guidelines as per the above overtap allowance explanation), you are essentially removing more of the thread depth, depth that was already lessened due to the shallower thread profile.

Let’s look at an example for an ASTM A193 Grade B7 bolt with 3”-8 UN Class 2A threads and an ASTM A194 Grade2H nut with 3”-8 UN Class 2B threads for plain finish, galvanized with an overtap of 0.027”, and galvanized with an overtap of 0.050”.

Minimum stripping resistance for the external threads:

In comparison, the minimum tensile strength of a 3”-8 UN A193 Grade B7 bolt is 748,000lbs.

So clearly, even a modest amount of overtapping drastically reduces the stripping resistance, in this case a full 70,000lbs, which is 9% below where we would normally expect the bolt to fail. As the overtap increases to 0.050”, the difference between tensile and stripping resistance is 224,000lbs, or a whopping 30%.

Another example, using a 2”-8 A193 Grade B7 bolt, breaks down as follows:

Minimum stripping resistance of the external threads:

In comparison, the minimum tensile strength of a 2”-8 UN A193 Grade B7 bolt is 346,000lbs.

So, like the first example, the thread stripping resistance of a plain finish fastener well exceeds the tensile strength of the bolt, but drastically decreases with overtapping. Overtapping 0.027” decreases the stripping resistance by 78,000lbs and is 36,000lbs below the minimum failure point of the fastener, and overtapping 0.050” decreases the stripping resistance by 146,000lbs which is 104,000lbs below the minimum failure point.

In summary, ASTM A563 is the only nut specification that addresses specific modifications to thread geometry and proof load values for hot-dip galvanized nuts. Therefore, only thread and pitch combinations listed in Table 5 of ASTM A563 (above) are recommended for hot-dip galvanized fasteners.

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Die seam on a hex head bolt

Answer: There are several differences between bolts intended for use in construction and more precision fasteners, such those used in an OEM application. One difference for headed bolts is the process in which the head is formed on the bolt and the resulting appearance of the bolts.

Larger, construction headed bolts are typically made by hot-forging the head of the bolt in an upsetter. When bolts are hot-forged, the steel is held between two gripper blocks which clamp the steel just under where the head is being formed, leaving die seam marks under the head of the bolt. Because the bolt heads are formed at a high temperature, there will also be a small amount of swelling under the head.

Per ANSI B18.2.1. hex bolts, heavy hex bolts,  and square head bolts,  “..may have a reasonable swell or fin under the head or die seam on the body not to exceed the basic bolt diameter by the following:

• 0.030 in. for sizes up to 1/2″
• 0.050 in. for sizes 5/8 and 3/4″
• 0.060 in. for sizes over 3/4″ to 1-1/4”
• 0.090 in. for sizes over 1-1/4” to 2”
• 0.120 in. for sizes over 2” to 3”
• 0.190 in. for sizes over 3”

Cap screws, which are generally more of a precision fastener, have no such allowances. Cap screws are typically manufactured through a different process, called cold heading. For hot-forged construction bolts however, die seams are perfectly allowable per the standards stated above.

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Damaged Anchor Bolts

Answer: The anchor rods in this photo were damaged because they were covered with snow and the equipment operator did not see them.

Every situation is different, and we try to not make recommendations where bent anchors are concerned as we feel it is a question better answered by the project engineer, as he/she will be more familiar with the specific situation.  That said, the AISC has this to say about repairing damaged anchor bolts:

“ASTM F1554 permits both cold and hot bending of anchor rods to form hooks; however, bending in the threaded area can be a problem.  It is recommended that only Grade 36 rods be bent in the field and the bend limited to 45° or less.  Rods up to about 1” in diameter can be cold bent.  Rods over 1” can be heated to 1,200° F to make bending easier.  It is recommended that bending be done using a rod bending device called a hickey.  After bending, the rods should be visually inspected for cracks.  If there is concern about the tensile strength of the anchor rod, the rod can be load tested.”

- 2^nd Edition of the AISC Design Guide 1, under Base Plate and Anchor Rod Design

So field bending F1554G36 is acceptable as long as it is not more than 45°, and is it done per the parameters in the above paragraph.  For other grades of anchor, or if the bend is more than 45°, the project engineer should be consulted in order to make the proper decision.

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