A325 TC bolts are twist-off tension control fasteners for structural steel joints. Each F1852 set is supplied as a matched assembly: a quenched-and-tempered medium carbon bolt, an A563 Grade DH heavy hex nut, and an F436 Type 1 washer. The splined tail shears off at the specified pretension, so the joint's tension is verified by looking at the bolt, not by reading a torque wrench.
Key Features
Splined Tail Proves the Pretension
The twist-off end breaks clean when tension reaches spec. Inspectors walk the joint and count sheared tails - no torque wrench, no turn-of-nut marking, no calibrated tool.
01
Matched Assembly,
One Lot
A325 TC bolts arrive as matched sets, with nut and washer hardness coordinated for pretension service. Swapping in a random replacement part breaks the lot traceability.
02
120 ksi Workhorse Grade
Tensile minimums are 120 ksi (827 MPa) through 1″ diameter and 105 ksi (724 MPa) above; yield is 92 ksi (634 MPa) up to 1″ and 81 ksi (558 MPa) beyond. Code-compliant strength without alloy-steel cost.
03
Three Finish Options
Plain black, hot-dip galvanized (A153), or mechanically galvanized (B695). Galvanized assemblies use over-tapped DH nuts and F436 washers.
04
Slip-Critical and Bearing-Type Rated
Covers both connection types under the RCSC Specification - the full pretensioned range in steel buildings, roof trusses, and bridge stringers.
05
Specifications
|
Item |
Specification |
|
Product Name |
A325 TC Bolt / A325 Tension Control Bolt |
|
ASTM Designation |
ASTM F3125 Grade F1852 |
|
Assembly |
Bolt + nut + washer, matched lot |
|
Material |
Quenched-and-tempered medium carbon steel |
|
Tensile |
120 ksi (827 MPa) min ≤1″; 105 ksi (724 MPa) min >1″ |
|
Yield |
92 ksi (634 MPa) min ≤1″; 81 ksi (558 MPa) min >1″ |
|
Proof Load |
85 ksi (586 MPa) |
|
Thread |
Class 2A (UNC) |
|
Head Type |
Heavy hex |
|
Nut |
A563 Grade DH heavy hex, over-tapped when galvanized |
|
Washer |
F436 Type 1 |
|
Finish |
Plain / Hot-dip galvanized (A153) / Mechanical galvanized (B695) |
|
Sizes |
1/2″ to 1-1/2″, nine sizes |
|
Lengths |
1-1/2″ to 6″ |
Applications
Steel Buildings
Column splices, beam-to-column moment connections, and roof trusses in commercial and low-rise frames.
Bridges & Transportation
Cross frames, diaphragms, and stringer connections on decks exposed to de-icing salt; HDG A325 TC bolts are the standard there.
Industrial & Plant
Mezzanines, pipe racks, equipment support frames, and conveyor structures; splined-tail inspection keeps repetitive connections moving without a torque audit.
Communication & Support Steel
Cell towers, billboard structures, and platform framing where one-sided wrench access matters.
FAQ
Q: Are A325 and F1852 the same bolt?
A: Yes. A325 is the legacy name; ASTM F3125 Grade F1852 is the current designation for the twist-off version. Both names point to the same 120 ksi structural bolt.
Q: Can A325 TC bolts be hot-dip galvanized?
A: Yes - to ASTM A153 or A123. Galvanized F1852 sets use over-tapped A563 DH nuts and F436 washers, the standard choice for bridge and coastal steel.
Q: How do I confirm correct tension on site?
A: The splined tail shears at the specified pretension. Walk the joint and count missing splines - that is the visual record. No torque audit required.
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