A490 TC bolts are twist-off tension control fasteners for the highest-strength structural connections. Grade F2280 delivers the largest pretension available in the ASTM structural range, so moment frames, crane runways, and machinery foundations get maximum clamp force per bolt.
Products Features
150 ksi on Every Diameter
Minimum tensile is 150 ksi (1035 MPa) with 130 ksi (896 MPa) yield and a 120 ksi (827 MPa) proof load - the strongest grade in ASTM F3125.
01
Alloy Steel, Hardened Through
The AISI 4140-type alloy core is quenched and tempered for uniform hardness across the full cross-section, so even the largest diameters hold rated tensile strength without weak spots.
02
Twist-Off, Self-Verifying
The spline breaks clean at the required pretension. A sheared tail is the quality record: the joint is tensioned, confirmed by counting during inspection.
03
Plain Finish Only
A490 TC bolts are specified in plain black finish only. Pickling and coating processes introduce hydrogen, and delayed fracture can follow under load. Corrosive outdoor connections call for a galvanized structural grade instead.
04
Grade-Marked Heads, Traceable Lots
The heavy hex head carries the A490 grade mark and the manufacturer's symbol, and each lot is supplied with MTRs so the alloy chemistry traces back to the heat.
05
Products Specifications
|
Item |
Specification |
|
Product Name |
A490 TC Bolt / A490 Tension Control Bolt |
|
ASTM Designation |
ASTM F3125 Grade F2280 |
|
Material |
Alloy steel (AISI 4140 type), quenched & tempered |
|
Tensile Strength |
150 ksi (1035 MPa) min, all diameters |
|
Yield Strength |
130 ksi (896 MPa) min |
|
Proof Load |
120 ksi (827 MPa) |
|
Thread |
UNC thread, Class 2A |
|
Head Type |
Heavy hex (per F3125) |
|
Nut |
A563 Grade DH, heavy hex |
|
Washer |
F436 Type 1 |
|
Finish |
Plain (black) only |
|
Assembly |
Bolt + nut + washer, matched lot |
|
Sizes |
1/2″ through 1-1/2″ |
|
Lengths |
1-1/2″–6″ |
Products Applications
High-Rise Moment Frames
Column-to-beam moment connections and transfer girders where drift and fatigue, not cost, govern the spec.
Crane & Heavy Lifting
Runway girders, monorail beams, and hoist support steel. A490 TC bolts resist the reversed and impact loading cranes apply to their support framing.
Heavy Industrial Plant
Mill buildings, furnace support steel, and machinery foundations in steel plants, smelters, and power stations.
Long-Span & Special Structures
Stadium trusses, theme-park ride steel, and long-span roofs where maximum clamp in minimum bolt count shortens erection time.
FAQ
Q: Why can't A490 TC bolts be galvanized?
A: Hydrogen embrittlement. 150 ksi alloy steel is prone to hydrogen-induced delayed fracture, and both pickling and galvanizing introduce hydrogen. F2280 is plain (black) finish only. For corrosive environments, use A325/F1852 HDG.
Q: Are A490 TC bolts reusable?
A: No. Once the spline tail has sheared, the assembly cannot be re-tensioned to a reliable load. RCSC treats twist-off bolts as single-use: a loosened or removed A490 TC bolt is replaced, never re-torqued.
Q: A490 or A325 - which TC bolt should I specify?
A: A490 for interior, maximum-load connections; A325 for outdoor or bridge steel that needs hot-dip galvanizing. If corrosion decides, choose A325; if clamp force decides, choose A490. Send the drawing if the call is unclear.
Send diameter, grip, and quantity - the quote follows with MTRs, lot traceability, and a lead time.
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