My company is looking to purchase A325SC, A325N, and A325X heavy hex structural bolts. What is the difference between these three?
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| TYPE 2 | Withdrawn November 1991.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 Type 2 was withdrawn in 1991 and no longer is in use.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.
I have an Engineer that’s specifying A490-SCA Bolts. Is this any different than Standard Slip Critical?
@Heber- No, A490 bolts are A490 bolts. The bolt itself is the same regardless of how it is used.
I am currently on a project that calls out to use A325-PT bolts. Can you tell me what the A325-PT bolts are used for? Thanks
@Ricky- PT means partial thread (as opposed to FT=full thread).
Is A325N, A325SC and A325TC bolts same? If not, then what are differences?
@Rajat- A325N and A325SC are connection types, so the bolts are the same regardless. A325TC is a bolt variety that performs the same function, but the TC stands for Tension Control. They are a round head bolt with a special spline and are installed with a special torque/tension hydraulic gun.
As it is there should be a difference between tread lengths between X and N bolts but where would we get the table for the bolts thread length
@Manoj- That is incorrect, all A325s, unless they are specially manufactured, will have the same thread length. When using them in X connections, you need to make sure that shims or extra washers are used in order to keep the threads out of the shear plane.
Are F1852TC and F1852SC same??If not what is the difference??
@Vamsi- TC typically means Tension Control which is a type of bolt with a spline drive that is designed to snap off at a predetermined tension. SC, at least in the realm of structural connections, means Slip Critical and describes a type of bolted joint, but not the bolt itself. We believe that TC bolts can be used in Slip Critical connections, and F1852 refers to an A325/120 strength tension control bolt, regardless of any additional letters.