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. 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TYPE 2 Withdrawn November 1991.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.

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 Type 2 was withdrawn in 1991 and no longer is in use.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.

The connection information provided in this FAQ is applicable to not only A325 heavy hex structural bolts, but to A490 structural bolts as well.

Written March 9, 2011 by
Kyle PettijohnKyle Pettijohn

Phone: 800.628.9472


    It is my understanding that galnanized A325 bolts are not to be used to connect weathereing steel components due to the reaction of these materials (coatings). Is this correct!
    With thanks, James M Kett

    @James Kett – There is a possibility of galvanic attack when dissimilar metals come into contact with each other, however it depends a little on the atmospheric (weather) conditions. We do not have any metallurgists on staff, so for your specific application, perhaps one should be contacted to be sure.

    Appreciate the A325, Type 2 Structural Bolt, was withdrawn in Nov,1991, was it due to lack of performance, (rebound capability)or was it related to actual bolt failure?

    Recently in one of my project I came to see a phrase “SPOIL THREAD”. Could anybody can help me on this.?

    @Sreejith- I have not heard that terminology before. My only guess is that they want you to damage one of the threads so that the nut will nut be able to back off.

    @Gopal- I believe what you are looking for is a F1852 TC bolt that is being used in a slip critical connection with the threads allowed in the shear plane. The N and SC designates how it is used, the bolt itself is not any different. You would need to determine the bolt diameter and length that is appropriate for your needs, and then we or another supplier could supply it.

    @Gopal- The designer will need to determine if he/she wants the threads in the shear plane of the joint or not. If the threads are to be excluded, then ‘X’ is designated, if the threads are allowable in the shear plane, then “N” is designated. The threads can be included or excluded by adjusting the bolt length or adding/subtracting washers.

    @Gopal- You are asking about three different items. A325 is a specific kind of structural bolt, grade 5 is a general purpose bolt, and grade 8 is a very high strength general purpose bolt. These are three separate bolts that are each used in their own applications.

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