There is no difference between these bolts. The “X”, “SC”, and “N” simply identify the type of connection the bolts are used in. “X” and “N” are bearing type connections, where the bolts are being used in shear.
“X” means these particular A325 heavy hex structural bolts will be used in a bearing type connection where the threads will be excluded from the shear plane, whereas “N” means the threads are included in the shear plane. “SC” signifies a slip-critical connection where the bolts are not being used in shear, but instead, the tension from the connection resists the shearing force. You simply require the same standard A325 heavy hex structural bolt but will be using them in three different connection types.
| SC | Slip-critical connection. |
|---|---|
| N | Bearing type connection with threads included in the shear plane. |
| X | Bearing-type connection with threads excluded from the shear plane. |
“SC”, “N”, and “X” specify solely the type of connections to use the A325 bolt in.
According to Note 2 in Section 3.8 (Ordering Information) of the new F3125 specification covering high strength structural bolts, “Bolts are sometimes detailed with names such as A325 HS, A325 SC, A325 x or A490 N. These names relate to connection design and bolt installation, but do not change the manufacturing requirements and are preferably not shown on bolt orders.”
There are other types of A325 bolts that do affect the type of bolt that needs to be purchased. For these, see the following chart.
| TYPE 1 | Medium carbon, carbon boron, or medium carbon alloy steel. |
|---|---|
| TYPE 2 | Withdrawn November 1991. |
| TYPE 3 | Weathering steel. |
| T | Fully threaded A325. (Restricted to 4 times the diameter in length) |
| M | Metric A325. |
| S | Modified thread length or head dimensions. |
The majority of A325 bolts being made in the market are A325 Type 1 and are available both plain and hot-dipped galvanized. Type 2 was withdrawn in 1991 and no longer is in use. Type 3 is a naturally corrosion-resistant weathering steel that typically is used in a plain finish (no finish). Availability for the steel can be limited and standard, mass-produced bolts start at 5/8″ diameter. Below 5/8″ diameter, heat-treatable weathering steel is not commonly available.
A325T bolts (covered under supplementary requirement (S1) of the A325 specification signifies that the A325 bolt must be completely threaded, but is limited to 4 times the diameter in length. Fully threaded A325 bolts longer than 4 times the diameter do not comply with the specification, will not be available in the marketplace, and technically cannot be manufactured. ASTM A449 should be considered in lieu of A325 bolts with extended threads that don’t meet the requirements of A325T. However, ASTM 3125, the new combined high strength structural bolting specification, added a new type S that allows for an A325 bolt to have altered thread length and head dimensions. Previously, altered thread lengths meant switching grades or accepting a bolt that didn’t technically conform to the A325 specification, but now marking the bolt head with an S allows for extended threads or using different head dimensions.
The connection information provided in this FAQ is applicable to not only A325 heavy hex structural bolts, but to A490 structural bolts as well.
Can we use A325N & A490N TC Bolts in Slip Critical Conditions/Connections?
@PP-The “N” designation has more to do with the joint/connection type than the bolt itself. The ‘N’ means that threads can be included in the shear plane. As for whether or not threads can be included in the shear plane in slip critical connections, we are not certain – you would need to contact a structural engineer or the AISC.
Is there any difference between A325 SC and A325 TC bolt in terms of tension and shear capacity?
Thanks in Advance.
@Tarkik- No, those two bolts are identical with respect to their mechanical properties.
In A325X bolts are used for SC connections?
@Kasi- There are three connection types, N, X, and SC. The connection type has nothing to do with the bolt itself, the same bolt is used in all. The difference is how the joint was designed, and whether it was designed to allow threads in the shear plane, exclude threads, or be slip critical. The individual joint design will dictate the connection type.
Looking for 3/4″ and 1/2″ dia A307 bolts for maximum and minimum length available…
@Sridhar- Normally, the shortest length available is about 1.5 times the diameter, so the shortest 1/2″ bolt would be 3/4″ long. For the maximum length, we can manufacture bolts to any length needed, up to 20 foot long and occasionally longer.
What is the maximum and minimum bolt length available for A307 bolts
@Sridhar- The available lengths will vary depending on the diameter, and can be as short as 1/2″ and as long as 36″+. Additionally, we are able to manufacture special length bolts if you are unable to find what you are looking for.