Heavy Hex Bolts Supplier

HEAVY HEX BOLTS - GENERAL

Heavy hex bolts have a head that is larger than a standard (finish) hex head. Standard heavy hex bolts are made of low to mid carbon steel. The large head offers a greater bearing surface that distributes the clamping load over a greater area.

The ASTM A307 specification covers carbon steel bolts and studs ranging from 1/4" through 4" diameter. This is your everyday, run of the mill bolt specification often manufactured using A36 round bar. There are three grades A, B, and C which denote tensile strength, configuration, and application.

The ASTM A193 standard covers alloy steel and stainless steel bolting materials for high temperature or high pressure service. This specification includes fasteners intended for use in pressure vessels, valves, flanges, and fittings. Although, this material is often available in UNC national coarse thread, diameters above one inch are typically specified 8 threads per inch (tpi).

ADDITIONAL SPECIFICATION

HEAVY HEX BOLTS - STRUCTURAL

Heavy hex structural bolts are designed for steel-to-steel structural connections. The ASTM A325 and A490 specifications cover high strength heavy hex structural bolts from 1/2" diameter through 1-1/2" diameter. These bolts are intended for use in structural connections and therefore have shorter thread lengths than standard hex bolts. The A325 and A490 specifications are not intended for general applications.

The ASTM A490 specification covers quenched and tempered, alloy steel, heavy hex structural bolts from 1/2" diameter through 1-1/2" diameter with a minimum 150 ksi tensile. A490 bolts are similar in application and dimensions to A325 Hex Cap Screws heavy hex structural bolts but are made from an alloy steel rather than a medium carbon steel, resulting in a higher strength fastener.

ADDITIONAL SPECIFICATION

GOVERNING STANDARDS

ASTM A307 - Standard Specification for Carbon Steel Bolts, Studs, and Threaded Rod 60 000 PSI Tensile Strength

ASTM A193 - Standard Specification for Alloy-Steel and Stainless Steel Bolting for High Temperature or High Pressure Service and Other Special Purpose Applications

ASTM A325 - Standard Specification for Structural Bolts, Steel, Heat Treated, 120/105 ksi Minimum Tensile Strength

ASTM A490 - Standard Specification for Structural Bolts, Alloy Steel, Heat Treated, 150 ksi Minimum Tensile Strength

DIN 6914 10 - Heavy Hexagon Structural Bolts

SUGGESTED STARTING VALUES

The estimated torque calculations are only offered as a guide.

Use of these tables by anyone is the sole responsibility of that person and they assume all risk.

Due to the many variables that affect the torque-tension relationship such as surface texture, and lubrication and human error, the only way to determine the correct torque is through experimentation.

Torque values calculated using formula T = KDP where T = Torque, K = torque coefficient (dimensionless), D = nominal diameter (inches), P = bolt clamp load, lb.

K Value: Plain, non-plated, as received condition = .20

Clamp Load = 75% of specified Proof Load

HEAVY HEX BOLTS

Bolt DiameterWidth Across FlatsWidth Across CornersHeight
1/2 7/8 1.01 11/32
5/8 1-1/16 1.227 27/64
3/4 1-1/4 1.443 1/2
7/8 1-7/16 1.66 37/64
1 1-5/8 1.876 43/64
1-1/8 1-13/16 2.093 3/4
1-1/4 2 2.309 27/32
1-3/8 2-3/16 2.526 29/32
1-1/2 2-3/8 2.742 1
1-3/4 2-3/4 3.175 1-5/32
2 3-1/8 3.608 1-11/32
2 1/4 3-1/2 4.041 1-1/2
2 1/2 3-7/8 4.474 1-21/32

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Torque Values for A307B Heavy Hex Bolts

Bolt DiameterMinimum Clamp LoadTightening Torque lb-ft
1/2 12000 100
5/8 19000 198
3/4 28,000 350
7/8 39,000 569
1 51,000 850
1-1/8 56,000 1,050
1-1/4 71,000 1,479
1-3/8 85,000 1,948
1-1/2 103,000 2,575

Torque Values for A325 Heavy Hex Bolts

Bolt DiameterMinimum Clamp LoadTightening Torque lb-ft
1/2 12000 105
5/8 19000 210
3/4 28,000 365
7/8 39,000 595
1 51,000 890
1-1/8 56,000 1,100
1-1/4 71,000 1,550
1-3/8 85,000 2,045
1-1/2 103,000 2,700

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Torque Values for A490 Heavy Hex Bolts

Bolt DiameterMinimum Clamp LoadTightening Torque lb-ft
1/2 15000 130
5/8 24000 265
3/4 35000 460
7/8 49000 750
1 64000 1120
1-1/8 80000 1575
1-1/4 102000 2230
1-3/8 121000 2910
1-1/2 148000 3885

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Torque Values for A193 B7 Heavy Hex Bolts

Bolt SizeClamp LoadTightening Torque lb-ft
1/4-20 2513 10
5/16-18 4125 21
3/8-16 6113 38
7/16-14 11150 61
1/2-13 11175 93
9/16-12 14325 134
5/8-11 17813 186
3/4-10 26288 329
7/8-9 36375 530
1-8 47738 796
1 1/8-8 82934 1166
1 1/4-8 78754 1641
1 3/8-8 97119 2226
1 1/2-8 117515 2938
1 3/4-8 163800 4778
2-8 218138 7271

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Heavy Hex Bolts - Mechanical Properties

GradeSizeTensile ksi minYield ksi min
A325 1/2" - 1 120 92
  1 1/8 - 1 1/2 105 81
A490 1/2 - 1 1/2 150 130
A193 B7 Up to 2 1/2 125 105
  2 5/8 - 4 115 95

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Structural Bolts

Inch GradeTensile Strength (Min)MaterialTreatment
A490 150,000 psi Alloy Steel  
A325 120,000 psi Carbon Steel  
B7 (A193) 125,000 psi Alloy Steel  
A307 60,000 psi Carbon Steel  

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