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 Hex Cap Screws
Hex cap screws are fully threaded hex bolts (DIN 933 / ISO 4017) machined from Incoloy 800H ASTM B408 round bar for high-temperature petrochemical and refinery service to 815 deg C (1500 deg F). Unlike partially threaded hex bolts (DIN 931) the hex cap screw carries thread from immediately under the head to the chamfered end, with no plain shank. This geometry is preferred on short grip lengths and where the bolt threads into a tapped hole rather than passing through to a nut. TorqBolt machines hex cap screws in diameter range M6 to M48 (metric) and 1/4 inch to 1-1/2 inch (inch). Across-flats follow the DIN 933 or ASME B18.2.1 schedule. Every hex cap screw 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, with type 3.2 third-party witness supplied on PO call-out for refinery and offshore procurement scope.
Hex Cap Screw Dimensions (DIN 933 / ISO 4017)
| Size designation | Across flats / OD | Head / nut height | Thread pitch | Standard reference |
|---|---|---|---|---|
| M6 | 6.0 mm OD | Head A/F 10 mm; Head height 4 mm | 1.0 mm | DIN 933 / ISO 4017 |
| M8 | 8.0 mm OD | Head A/F 13 mm; Head height 5.3 mm | 1.25 mm | DIN 933 / ISO 4017 |
| M10 | 10.0 mm OD | Head A/F 16 mm; Head height 6.4 mm | 1.5 mm | DIN 933 / ISO 4017 |
| M12 | 12.0 mm OD | Head A/F 18 mm; Head height 7.5 mm | 1.75 mm | DIN 933 / ISO 4017 |
| M16 | 16.0 mm OD | Head A/F 24 mm; Head height 10 mm | 2.0 mm | DIN 933 / ISO 4017 |
| M20 | 20.0 mm OD | Head A/F 30 mm; Head height 12.5 mm | 2.5 mm | DIN 933 / ISO 4017 |
| M24 | 24.0 mm OD | Head A/F 36 mm; Head height 15 mm | 3.0 mm | DIN 933 / ISO 4017 |
| M30 | 30.0 mm OD | Head A/F 46 mm; Head height 18.7 mm | 3.5 mm | DIN 933 / ISO 4017 |
| M36 | 36.0 mm OD | Head A/F 55 mm; Head height 22.5 mm | 4.0 mm | DIN 933 / ISO 4017 |
| M48 | 48.0 mm OD | Head A/F 75 mm; Head height 30 mm | 5.0 mm | DIN 933 / ISO 4017 |
Manufacturing Route at TorqBolt
Hex cap screw manufacture follows the same process route as hex bolts but with thread coverage extended to the head underside:
- Receive Incoloy 800H bar to ASTM B408; PMI verification.
- Cut bar to overall length on bandsaw.
- CNC turn the shank to print OD; face head-end square.
- Mill hex head per DIN 933 across-flats; controlled head-height tolerance.
- Thread roll the full-length shank: thread to head-underside, no plain shank.
- Verify class 6g per ISO 965 with ring + plug gauges.
- Solution anneal at 1149 deg C plateau followed by rapid quench; grain size 5 verified.
- Hardness band 120-184 HB; visual + dimensional + PMI inspection 100 percent.
- Head-mark heat number + grade (800H); VCI wrap; CoC + EN 10204 cert.
Hex Cap Screw Sizes Stocked and Lead Times
| Diameter range | Length range | Stock status | Lead time |
|---|---|---|---|
| M6 - M12 | 10 mm - 80 mm | Stock + ex-stock | 7 working days |
| M16 - M24 | 20 mm - 150 mm | Made-to-order from stock bar | 10 to 14 working days |
| M30 - M36 | 30 mm - 200 mm | Made-to-order | 14 to 21 working days |
| M48 | 40 mm - 250 mm | Made-to-order, large bar | 3 to 5 weeks |
Inspection and Heat Marking
Hex cap screw specific inspections cover full-length thread engagement and head-underside thread runout:
- Full-length thread verified with class 6g ring gauge full-traverse.
- Thread runout under head verified per DIN 933 tolerance.
- Hex head across-flats and head-height verified with go / no-go gauges.
- Hardness band 120-184 HB on first piece and one per batch.
- ASTM E112 grain-size etch verification (grain size 5 or coarser).
- PMI by X-ray fluorescence on first piece and one per batch.
- Heat number + grade marking on head.
- Visual inspection for thread damage and head-corner cracking.
Typical Service Conditions
Hex cap screws are specified where the screw threads directly into a tapped boss and no nut is used, or where short grip length precludes a partial-thread bolt:
- Tapped-boss bolting on ASME Section VIII pressure-vessel manhole covers.
- Short grip-length flange bolting on heat exchanger shell covers.
- Reformer pigtail bracket and clamp bolting into tapped vessel bosses.
- Furnace component fastening into tapped refractory anchors.
- Steam superheater support-bracket bolting into tapped header bosses.
- Combustion-air ductwork bracket fastening with full-length thread engagement.
Incoloy 800H Alloy Considerations on This Fastener Form
Companion Fasteners and Related Pages
- Hex Bolts: partial-thread DIN 931 alternative.
- Heavy Hex Bolts: ASME B18.2.1 heavy-pattern alternative.
- Socket Head Cap Screws: Allen-drive alternative for restricted clearance.
- Hex Nuts: matched DIN 934 nuts when through-bolted.
- Threaded Rod: cut-to-length continuous-thread alternative.
Frequently Asked Questions
Q. When to use hex cap screw vs hex bolt?
Hex cap screw (DIN 933, fully threaded) is preferred on short grip lengths and tapped-hole assemblies. Hex bolt (DIN 931, partially threaded) is preferred on through-bolt assemblies with longer grip lengths where the plain shank carries the bearing load.
Q. What is the maximum length for hex cap screws?
DIN 933 standard length range is 6 mm to 200 mm. Longer lengths default to DIN 931 hex bolts (partially threaded). Long fully threaded variants are machined on PO call-out.
Q. Are hex cap screws available with under-head fillet radius?
Yes. Default fillet radius is per DIN 933. Larger fillets for fatigue-critical applications are machined on PO call-out.
Q. Can hex cap screws be supplied in inch sizes?
Yes. ASME B18.2.1 fully threaded hex cap screws 1/4 inch through 1-1/2 inch are machined on PO call-out from B408 bar with class 2A UNC threads.
Q. What head-marking is applied?
Heat number + grade designation (800H) + TorqBolt mark on the head per ASTM B408 traceability requirement.
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