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A490/A490M Heavy hex structural bolts


Heavy Hex Bolts

SeveralASTM specificationsrequire a hex head that is larger than a standard (finished) hex head. These specifications include: A193, A320and A307B. Although A325 andA490bolts also require a heavy hex head, please refer to Structural Boltsfor dimensional specifications, since these bolts have shorter thread lengths than standard heavy hex bolts.


Taida Bolt manufactures heavy hex bolts from 1/2" diameter through 2-1/2" diameter in most ASTM, AASHTO, and SAE specifications. Special tooling can be created to produce nonstandard head dimensions or bolt heads with your company's name and/or logo.



The ASTM A490 specification covers quenched and tempered, alloy steel, heavy hex structural bolts from ½” diameter through 1½” diameter with a minimum 150 ksi tensile. These bolts are intended for use in structural connections and therefore have shorter thread lengths than standard hex bolts. Refer to the Structural Bolts page of our site for thread lengths and other related dimensions. A490 bolts are similar in application and dimensions to A325 heavy hex structural bolts but are made from an alloy steel rather than a medium carbon steel, resulting in a higher strength fastener.

The A490 specification is applicable to heavy hex structural bolts only. For bolts with different thread lengths than specified for structural bolts but with similar mechanical properties, see Specification A354 grade BD.

ASTM A490 bolts shall not be coated by hot-dip galvanizing, mechanical deposition, or electroplating with zinc or other metallic coatings due to the potential risk of hydrogen embrittlement.

Additional testing in the form of Magnetic Particle Inspection for Longitudinal Discontinuities and Transverse Cracks is a requirement of the A490 specification.



Medium carbon and alloy steel.


Withdrawn in 2002.


Weathering steel.




Metric A490.

Connection Types


Slip critical connection.


Bearing type connection with threads included in the shear plane.


Bearing type connection with threads excluded from the shear plane.

Mechanical Properties


Tensile, ksi

Yield, ksi

Elong. %, min

RA %, min

1/2 - 1-1/2





Recommended Nuts and Washers



Type 1

Type 3

Type 1

Type 3





Note: Nuts conforming to A194 Grade 2H are a suitable substitute for use with A490 heavy hex structural bolts. Follow the link for an ASTM A563 Nut Compatibility Chart.


1.        The bolts shall not be coated by hot-dip zinc coating, mechanical deposition, or electroplating with zinc or othtransverse crackser metallic coatings due to the potential for hydrogen embrittlement. Read more about issues with galvanizing ASTM A490.

2.        Each sample representative of the lot shall be magnetic particle inspected for longitudinal discontinuities and .

  • Studs ASTM A193 B7 / ASTM A194 2H
  • Stud bolts ASTM A193 B7—ASTM A194 2H
  • Threaded rods ASTM A193 B7
  • Socket cap fasteners Din 912
  • Din912 Socket cap fasteners
  • Din7991
  • A325/A563/F436 Heavy hex structural bolts
  • A490/A490M Heavy hex structural bolts
  • ASTM A325/325M/A490/490M
  • A325/A325M ZP Heavy hex structural bolts
  • A194 2H/2HM / A563 Heavy Hex Nuts
  • ASTM A307 Carriage Bolts
  • IFI Hex Cap Bolts
  • Din931
  • Din933
  • Din558
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