Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
Incoloy 800H Heavy Hex Bolts
Incoloy 800H heavy hex bolts to ASME B18.2.1 are the US-spec standard for high-temperature flange bolting and pressure-vessel assemblies on petrochemical, refinery and steam-cycle service. TorqBolt machines heavy hex bolts from ASTM B408 round bar in inch range 1/2 inch through 2 inch with metric equivalents M12 to M52 on call-out. The heavy hex head carries a larger across-flats and a thicker head-height than the standard hex bolt (DIN 931) to deliver higher bearing area under torque-controlled tightening. The shank is partially threaded with class 2A inch threads per ASME B1.1 (class 6g metric on call-out). Every heavy hex bolt ships with EN 10204 type 3.1 mill test certificate documenting heat number, ASTM B408 chemistry, solution-anneal cycle (1149 deg C plateau, rapid quench) and ASTM grain size 5 verification. Heavy hex bolts are the US-spec counterpart to DIN 931 hex bolts on ASME Section VIII pressure-vessel scope.
Heavy Hex Bolt Dimensions (ASME B18.2.1)
| Size designation | Across flats / OD | Head / nut height | Thread pitch | Standard reference |
|---|---|---|---|---|
| 1/2 inch | 0.500 inch OD | A/F 7/8 inch; Head height 5/16 inch | 13 tpi UNC | ASME B18.2.1 |
| 5/8 inch | 0.625 inch OD | A/F 1-1/16 inch; Head height 25/64 inch | 11 tpi UNC | ASME B18.2.1 |
| 3/4 inch | 0.750 inch OD | A/F 1-1/4 inch; Head height 15/32 inch | 10 tpi UNC | ASME B18.2.1 |
| 7/8 inch | 0.875 inch OD | A/F 1-7/16 inch; Head height 35/64 inch | 9 tpi UNC | ASME B18.2.1 |
| 1 inch | 1.000 inch OD | A/F 1-5/8 inch; Head height 39/64 inch | 8 tpi UNC | ASME B18.2.1 |
| 1-1/8 inch | 1.125 inch OD | A/F 1-13/16 inch; Head height 11/16 inch | 7 tpi UNC | ASME B18.2.1 |
| 1-1/4 inch | 1.250 inch OD | A/F 2 inch; Head height 25/32 inch | 7 tpi UNC | ASME B18.2.1 |
| 1-1/2 inch | 1.500 inch OD | A/F 2-3/8 inch; Head height 15/16 inch | 6 tpi UNC | ASME B18.2.1 |
| 1-3/4 inch | 1.750 inch OD | A/F 2-3/4 inch; Head height 1-3/32 inch | 5 tpi UNC | ASME B18.2.1 |
| 2 inch | 2.000 inch OD | A/F 3-1/8 inch; Head height 1-7/32 inch | 4.5 tpi UNC | ASME B18.2.1 |
Manufacturing Route at TorqBolt
Heavy hex bolt manufacture uses CNC turn-mill in two setups to produce the larger head profile, then thread roll the partial-thread section:
- Receive Incoloy 800H bar to ASTM B408; PMI verification on each heat.
- Cut bar to overall length on bandsaw (heavy hex head height + shank + thread length).
- CNC turn the shank to print OD; face head-end square; centre-drill for chucking.
- Mill heavy hex head: 6-sided across-flats per ASME B18.2.1 (larger A/F than standard hex), controlled head-height.
- Reverse part; thread roll the partial-thread section: class 2A UNC per ASME B1.1.
- Ring + plug gauge verification of threads.
- Solution anneal at 1149 deg C plateau followed by rapid quench; ASTM grain size 5 verified.
- Hardness band 120-184 HB; visual + dimensional + PMI inspection 100 percent.
- Head-mark heat number + grade (800H) + TorqBolt; VCI wrap; pack with matched heavy hex nuts.
Heavy Hex Bolt Sizes Stocked and Lead Times
| Diameter range | Length range | Stock status | Lead time |
|---|---|---|---|
| 1/2 inch - 1 inch | 1 inch - 8 inch | Stock + ex-stock | 7 working days |
| 1-1/8 inch - 1-1/2 inch | 2 inch - 12 inch | Made-to-order from stock bar | 10 to 14 working days |
| 1-3/4 inch - 2 inch | 3 inch - 18 inch | Made-to-order, large bar | 3 to 5 weeks |
| Above 2 inch | Per print | Forged blank required | 5 to 7 weeks |
Inspection and Heat Marking
Heavy hex bolt specific inspections cover the larger head geometry and inch-thread compliance:
- Heavy hex head across-flats verified per ASME B18.2.1 schedule with go / no-go gauge.
- Head height per ASME B18.2.1 tolerance band.
- Shank diameter measured at three points along length; OD per print.
- Thread engagement verified with class 2A UNC ring + plug gauges per ASME B1.1.
- Hardness band 120-184 HB on first piece and one per batch.
- ASTM E112 grain-size etch verification.
- PMI by X-ray fluorescence on first piece and one per batch.
- Head-marked with heat number + grade (800H) for traceability per ASTM B408.
Typical Service Conditions
Heavy hex bolts are the US-spec standard on ASME Section VIII pressure-vessel and petrochemical flange bolting:
- ASME Section VIII Division 1 pressure-vessel flange bolting above 540 deg C.
- Ethylene cracker US-spec petrochemical radiant-section flange bolting.
- Heat exchanger shell flange bolting on US-spec refinery service.
- Steam superheater final-stage flange bolting on US-spec waste-heat boilers.
- Reformer pigtail outlet flange bolting on US-spec hydrogen plants.
- Refinery fired-heater radiant-section flange bolting per API 660 heat-exchanger scope.
Incoloy 800H Alloy Considerations on This Fastener Form
Companion Fasteners and Related Pages
- Hex Bolts: DIN 931 metric alternative for European-spec scope.
- Heavy Hex Nuts: matched ASME B18.2.2 nuts.
- Hex Cap Screws: fully threaded variant.
- Stud Bolts: no-head stud bolt alternative.
- Socket Head Cap Screws: Allen-drive alternative for restricted-clearance assemblies.
Frequently Asked Questions
Q. What is the difference between heavy hex and standard hex bolts?
Heavy hex has larger across-flats and thicker head-height than standard hex (per ASME B18.2.1 vs ASME B18.2). The larger head delivers higher bearing area under torque-controlled tightening and is the US-spec standard on pressure-vessel and refinery flange bolting.
Q. Are Incoloy 800H heavy hex bolts available in metric sizes?
Yes on call-out. Standard supply is inch (1/2 inch - 2 inch). Metric M12-M52 to DIN 6914 (German heavy hex) is machined to print on PO call-out.
Q. What is the thread tolerance class supplied?
ASME B1.1 class 2A external thread default for inch supply. Class 3A on PO call-out for high-precision assembly. ISO 965 class 6g for metric supply.
Q. Can heavy hex bolts be supplied with through-hole drilled for safety wire?
Yes on PO call-out. Cross-drilled or castellated heads for safety-wire applications are machined to print on special order.
Q. Do you supply heavy hex bolts with washers as a set?
Yes. Default supply is heavy hex bolt + matched heavy hex nut + optional flat washer. Washer specification is per PO call-out.
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