OEM manufacturer ASME B18.2.1 · ISO 4014 · ISO 4017 · IS 1364 · ASTM F3125
Hex & Heavy Hex Bolts — ASME B18.2.1
Hex and heavy hex bolts are headed bolts tightened with a spanner on the hexagon head and a matching nut. Teshi Group manufactures them to ASME B18.2.1, ISO 4014/4017 and IS 1364 in carbon steel, alloy steel and stainless steel grades for piping, structural and equipment use.
Also called: hex head bolts, heavy hex bolts, hexagon bolts, structural bolts, machine bolts
What are Hex & Heavy Hex Bolts?
A hex bolt has a six-sided head forged or machined on one end and a threaded shank, either partly threaded or fully threaded. Heavy hex bolts have a larger, thicker head for the same diameter, which spreads load over a bigger bearing area and suits high-strength structural joints and pressure bolting with heavy hex nuts. Hex bolts are chosen where a fixed head is convenient, such as one-side access, equipment bases and structural steel connections. For pressure flanges, stud bolts are usually specified instead.
Key features
- Hex and heavy hex heads per ASME B18.2.1; metric to ISO 4014 (part thread) and ISO 4017 (full thread)
- Heavy hex heads are ⅛" larger across flats than standard hex for the same diameter
- Grades from general purpose ASTM A307 to high-strength ASTM F3125 (A325 / A490) and A193 B7
- Stainless steel A193 B8/B8M and ISO 3506 A2/A4 options
- Supplied with matching nuts and washers as sets
Specification
| Supply | OEM manufacturer — Teshi Group, India |
|---|---|
| Standard | ASME B18.2.1 (inch), ISO 4014 / ISO 4017 (metric), IS 1364 |
| Head types | Hex, heavy hex; part threaded or fully threaded |
| Grades — carbon steel | ASTM A307 Gr A / B, ASTM A563 nuts, SAE J429 Gr 2 / 5 / 8, ISO 898-1 class 4.6, 5.6, 8.8, 10.9, 12.9; ASTM F3125 (A325, A490) |
| Grades — alloy steel | ASTM A193 B7, B7M, B16; nuts ASTM A194 2H, 2HM, 3, 7, 7M, 16 |
| Grades — low-temperature | ASTM A320 L7, L7M, L43; nuts ASTM A194 7 / 7M with S3 impact test |
| Grades — high-temperature | ASTM A453 Gr 660 (A286, UNS S66286); ASTM A193 B16 |
| Grades — stainless steel | ASTM A193 / A320 B8, B8M, B8T, B8C (Class 1 and Class 2); nuts ASTM A194 8, 8M, 8T, 8C, 8F; ISO 3506 A2-70, A4-70, A4-80; ASTM F593 / F594 |
| Grades — 904L and 6Mo | 904L (UNS N08904), 254 SMO / 6Mo (UNS S31254) |
| Grades — duplex and super duplex | Duplex UNS S31803 / S32205 and super duplex UNS S32750 / S32760 (ASTM A1082 bolting, A276 / A479 bar) |
| Grades — nickel alloys | Monel 400 (ASTM B164, N04400), Monel K-500 (B865, N05500), Inconel 600 (B166, N06600), Inconel 625 (B446, N06625), Inconel 718 (B637, N07718), Incoloy 825 (B425, N08825), Hastelloy C276 (B574, N10276), Alloy 20 (B473, N08020) |
| Grades — titanium | ASTM B348 Grade 1, 2, 5 (Ti-6Al-4V), 7, 12 |
| Grades — copper-nickel | Cu-Ni 90/10 (C70600) and 70/30 (C71500) against order |
| Grade availability | Every grade listed is made or supplied against order, with EN 10204 3.1 certificates (3.2 / third-party inspection when specified) and PMI on alloy, stainless, duplex and nickel grades. |
| Threads | UNC / UNF / 8UN, ISO metric coarse and fine |
| Coatings | Plain, PTFE/Xylan (fluoropolymer), hot-dip galvanised, zinc / zinc-nickel electroplated, as ordered |
| Testing | Proof load, tensile, hardness; PMI on alloy and stainless grades |
| Documents | EN 10204 3.1 mill test certificate (3.2 / third-party inspection when specified), dimensional inspection report |
Applications
- Structural steel connections and pipe racks
- Equipment and pump bases
- Pipe supports and clamps
- Valve and actuator mounting
- Plant and machinery assembly
Hex bolt vs heavy hex bolt
For the same thread diameter, a heavy hex bolt has a head ⅛" wider across flats and slightly taller than a standard hex bolt, per ASME B18.2.1. The bigger head gives more bearing area, which reduces embedment and suits high-strength structural bolts (ASTM F3125 A325 and A490 are heavy hex) and pressure bolting. Standard hex bolts are used for general assembly where loads are lower.
Technical data sheets
FAQ
Hex & Heavy Hex Bolts: common questions
Are ASTM A325 bolts still a separate standard?
No. ASTM A325 and A490, together with F1852 and F2280, were consolidated into ASTM F3125. They are now ordered as F3125 Grade A325 or Grade A490 heavy hex structural bolts, and we supply them on that basis.
What is the difference between ISO 4014 and ISO 4017?
Both are metric hexagon head bolts. ISO 4014 has a partly threaded shank, while ISO 4017 is threaded to the head (commonly called a hex screw or full-thread bolt).
Which nut goes with a heavy hex bolt?
Heavy hex bolts are normally used with heavy hex nuts of matching grade, for example ASTM A563 DH or A194 2H nuts for high-strength structural or pressure bolting.
Can hex bolts be used on pressure flanges?
Headed bolts are permitted on some low-class flanges, but most piping specifications call for stud bolts with two heavy hex nuts. Follow the project piping class.
Need a size or grade not listed here?
Our engineering team manufactures against your drawing or datasheet, with dimensional sign-off before dispatch.
Send us your specificationTraceability
From mill heat to your site
- 01
Approved mill material
Received against the mill certificate; heat number registered.
- 02
Forging & machining
Heat number carried through every stage in our Indian works.
- 03
PMI, dimensional & NDT
Every lot inspected to the governing standard; TPI witness on request.
- 04
Stamped & certified dispatch
Hard-stamped pieces with EN 10204 3.1 / 3.2 certificates.
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