Standards
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175 / ISO 15156-2
- NORSOK M-650 Qualified
- API 6A Certified
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
Incoloy 925 Hex Cap Screws (UNS N09925)
Finished hex-head bolts (precision tolerance) ASME B18.2.1 / ISO 4014 — washer face, chamfered point
Incoloy 925 hex cap screws (UNS N09925) are the precision-tolerance finished variant of the standard hex bolt. Per ASME B18.2.1, hex cap screws differ from hex bolts in three ways: (1) tighter dimensional tolerance class on body diameter and head dimensions, (2) integral washer face under the head bearing surface (a small chamfered circular pad that bears uniformly on the joint), and (3) chamfered point on the threaded end (vs the rolled / flat end of a hex bolt). The combination gives a higher-quality fastener for precision applications, rotating-machinery service, valve internals, instrument mounting, and any joint where the bolt rotates against a metallic seating surface during make-up. The "cap screw" name is historical (US convention); ISO 4014 covers metric cap screws / bolts under "Hexagon Head Bolts, Product Grades A and B" (Grade A = cap-screw precision; Grade B = standard). TorqBolt manufactures Incoloy 925 hex cap screws in M6 to M48 (1/4" to 2") sizes in the solution-annealed and aged condition (per heat-treatment specification) with 100% hardness inspection ensuring the 35 HRC NACE MR0175 sour-service cap.
Need Incoloy 925 hex cap screws? Email info@torqbolt.com with diameter × length, thread reach (full or partial), thread series (UNC / UNF / metric), tolerance class (Grade A / B), quantity, applicable standards (NACE MR0175 stamp). WhatsApp +91-22-66157017.
Hex Cap Screw Variants Manufactured
| Variant | Description | Standard | Use |
|---|---|---|---|
| Hex cap screw (Grade A precision) | Tight tolerance on body + head; integral washer face; chamfered point | ASME B18.2.1 / ISO 4014 Grade A | Rotating machinery, precision joints, finished-surface applications |
| Hex cap screw (partial thread, Grade A) | Plain shank below head + threaded tip; precision shank diameter | ASME B18.2.1 / ISO 4014 Grade A | Shear-loaded joints, hinge / pivot bolts |
| Hex cap screw (full thread, Grade A) | Threaded full length under head; precision dimensional tolerance | ASME B18.2.1 / ISO 4017 Grade A | Adjustable-grip joints; tapped-hole bolting in machinery |
| ASME B1.13M / DIN 933 finished hex screw | Full-thread metric variant with cap-screw tolerance | DIN 933 | European machinery + precision engineering |
| Hex flange cap screw | Integral flange (larger washer face) under hex head | ASME B18.2.1 | Vibration-prone joints; reduces clamping-stress concentration |
Standard Size Range & Thread Series
| Diameter | UNC (inch) | UNF (inch) | Metric Coarse | AF (B18.2.1) | Washer-face dia min | Length Range |
|---|---|---|---|---|---|---|
| 1/4" / M6 | UNC 20 | UNF 28 | M6 × 1.0 | 7/16" / 10 mm | 0.401" / 9.78 mm | 13 to 100 mm |
| 5/16" / M8 | UNC 18 | UNF 24 | M8 × 1.25 | 1/2" / 13 mm | 0.464" / 12.78 mm | 16 to 120 mm |
| 3/8" / M10 | UNC 16 | UNF 24 | M10 × 1.5 | 9/16" / 17 mm | 0.526" / 16.78 mm | 20 to 150 mm |
| 7/16" / M12 | UNC 14 | UNF 20 | M12 × 1.75 | 5/8" / 19 mm | 0.589" / 18.78 mm | 20 to 175 mm |
| 1/2" / M14 | UNC 13 | UNF 20 | M14 × 2.0 | 3/4" / 22 mm | 0.708" / 21.73 mm | 25 to 200 mm |
| 9/16" / M16 | UNC 12 | UNF 18 | M16 × 2.0 | 13/16" / 24 mm | 0.770" / 23.73 mm | 25 to 250 mm |
| 5/8" / M18 | UNC 11 | UNF 18 | M18 × 2.5 | 15/16" / 27 mm | 0.895" / 26.73 mm | 30 to 300 mm |
| 3/4" / M20 | UNC 10 | UNF 16 | M20 × 2.5 | 1-1/8" / 30 mm | 1.082" / 29.67 mm | 30 to 300 mm |
| 7/8" / M22 | UNC 9 | UNF 14 | M22 × 2.5 | 1-5/16" / 32 mm | 1.269" / 31.67 mm | 40 to 350 mm |
| 1" / M24 | UNC 8 | UNF 12 | M24 × 3.0 | 1-1/2" / 36 mm | 1.456" / 35.61 mm | 40 to 400 mm |
| 1-1/8" / M30 | UNC 7 | UNF 12 | M30 × 3.5 | 1-11/16" / 46 mm | 1.643" / 45.61 mm | 50 to 400 mm |
| 1-1/4" / M33 | UNC 7 | UNF 12 | M33 × 3.5 | 1-7/8" / 50 mm | 1.830" / 49.61 mm | 60 to 500 mm |
| 1-3/8" / M36 | UNC 6 | UNF 12 | M36 × 4.0 | 2-1/16" / 55 mm | 2.017" / 54.55 mm | 65 to 500 mm |
| 1-1/2" / M39 | UNC 6 | UNF 12 | M39 × 4.0 | 2-1/4" / 60 mm | 2.204" / 59.55 mm | 75 to 500 mm |
| 1-3/4" / M45 | UNC 5 | M45 × 4.5 | 2-5/8" / 70 mm | 2.578" / 69.55 mm | 90 to 500 mm | |
| 2" / M48 | UNC 4.5 | M48 × 5.0 | 3" / 75 mm | 2.952" / 74.49 mm | 100 to 500 mm |
Tolerance class: Grade A (precision cap screw) holds body diameter to ~0.0030′′ tolerance and head AF to ~0.005′′; Grade B (standard hex bolt) holds body to ~0.020′′ and head AF to ~0.020′′. Specify Grade A at RFQ stage if the application is rotating machinery, valve service, or any joint requiring repeatable preload.
Mechanical Property Requirements
| Property | Aged Condition (ASTM B805 min) |
|---|---|
| Tensile Strength | 165 ksi (1140 MPa) min |
| 0.2% Yield Strength | 110 ksi (760 MPa) min |
| Elongation in 4D | 18% min |
| Reduction of Area | 25% min |
| Hardness | 32–35 HRC (NACE sour-service cap) |
| Charpy V-notch at -46°C | 40 J min (NACE sour service) |
Applicable Standards
- ASTM B805, UNS N09925 forging stock (input)
- ASME B18.2.1, Square, Hex, Heavy Hex, and Askew Head Bolts (inch series, Grade A cap screw)
- ISO 4014, Hexagon Head Bolts, Product Grades A and B (metric, partial thread)
- ISO 4017, Hexagon Head Screws, Product Grades A and B (metric, full thread)
- DIN 933 / DIN 931, German metric hex cap screws (full / partial thread)
- ASTM A193 Grade B8N, Bolting Materials for High-Temperature or High-Pressure Service
- ASTM F2281, Standard Specification for Stainless Steel and Nickel-Alloy Bolts
- API 6A, Wellhead and Tree Equipment
- NACE MR0175 / ISO 15156-3, Table A.10 sour-service qualification
- NORSOK M-630 MDS A30, Norwegian Continental Shelf bolting
- EN 10204 3.1 / 3.2, certification
API 6A PSL Documentation Levels
| PSL | Pressure Class | Charpy | NDE |
|---|---|---|---|
| PSL-1 | 2,000–5,000 psi | Not required | Visual |
| PSL-2 | 5,000–10,000 psi | Not required | UT or MT |
| PSL-3 | 10,000–15,000 psi | 27 J at -29°C | 100% UT |
| PSL-3G | 10,000–15,000 psi gas | 27 J at -46°C / -101°C | 100% UT + grain size |
| PSL-4 | 15,000–20,000 psi | 40 J at -46°C | 100% UT + 100% MT + TPI witness |
Manufacturing Sequence
- Bar input: Incoloy 925 round bar per ASTM B805 in annealed condition. Tighter starting-bar tolerance than standard hex bolt to support the cap-screw precision class.
- Head upset (cold): Hex head formed by cold-upset on a header press. Cold upset is preferred for cap screws because the controlled-temperature cold flow produces tighter dimensional tolerance than warm upset.
- Washer-face machining: Integral washer-face pad turned on the head bearing surface to ASME B18.2.1 dimensional spec (typically 0.030′′ height with 30° chamfer). Critical, this is the precision feature distinguishing cap screw from hex bolt.
- Body grinding: Plain shank diameter ground to Grade A tolerance (~0.003′′ total). Standard hex bolts skip this step (turning only).
- Thread cutting / rolling: Threads applied in solution-annealed condition. Thread rolling preferred for cap screws (improves fatigue + matches cap-screw precision tolerance class).
- Point chamfer: Chamfered point ASME B18.2.1 (~30° chamfer at thread end), allows easier nut starting + protects thread end from damage.
- Solution anneal + age cycle: Per heat-treatment specification, 1900°F WQ + 1365°F × 8h FC + 1150°F × 8h AC.
- Final inspection: Cap-screw precision dimensional check (body diameter, head AF, washer-face diameter + height, point chamfer); thread gauging Go / No-Go; 100% Rockwell hardness; sample tensile + Charpy.
- Marking: Each cap screw stamped on head face with grade designation + heat number + standard reference + NACE stamp (sour orders).
Companion Components
- Hex nuts, standard mating nut ASME B18.2.2
- Heavy hex nuts, high-load mating nut
- Flat washers, though cap screw has integral washer face, additional flat washer may be specified for joint clearance
- Spring / lock washers, vibration retention
- Thread compound, sulphur-free, copper-free anti-seize per API RP 7A1
Application Examples
- Centrifugal pump casing bolts: Sour-service pumps where the bolt rotates against the casing seating surface during make-up
- Compressor cylinder head bolts: Reciprocating sour-gas compressor head retention with precision tolerance
- Valve body bolts: Where the head must seat uniformly against a finished bonnet face (see surface safety valve internals)
- Bearing housing bolts: Rotating-machinery bearing-cap retention
- Gearbox cover bolts: Sour-service gearbox case-half retention
- Instrument flange mounting: Pressure-transmitter / temperature-sensor mounting in sour service
- Subsea instrument enclosure bolts: Where the precision washer face provides better gasket sealing
- Hinge / pivot bolts: Where the bolt acts as a precision shear pin in the plain-shank region
Standard Coatings & Finishes
- Bare (passivated): Per ASTM A380 / A967, standard sour-service finish
- PTFE coating: Xylan 1424 / 1070, reduces friction during make-up; improves accuracy of torque-to-tension correlation in precision applications
- Phosphate + oil: MIL-DTL-16232 + light oil for storage protection
- Cad plate / hot-dip galvanise: NOT applied for nickel-alloy CRA service
Frequently Asked Questions
What's the difference between a hex bolt and a hex cap screw? Dimensionally similar externally but ASME B18.2.1 specifies tighter tolerance for hex cap screws (closer-toleranced head + body dimensions, integral washer face under head, chamfered thread end). Hex bolts are general structural use; cap screws are for precision applications like rotating machinery and valve internals where uniform bearing pressure under the head matters.
What does "Grade A" vs "Grade B" mean for ISO 4014 hex bolts? ISO 4014 covers both grades in one standard. Grade A = precision cap-screw tolerance (tight body diameter, tight head AF, washer face); Grade B = standard hex-bolt tolerance (looser dimensions, no washer face). For ISO-specified projects, "ISO 4014 Grade A" is the metric equivalent of ASME B18.2.1 hex cap screw.
Why does the washer face matter? The washer face provides a controlled-area circular bearing pad on the head, ensuring uniform contact pressure on the joint surface. Without it (standard hex bolt), the bearing area is the entire underhead surface, which can have irregularities from the upset-forging operation. For precision applications, rotating machinery where preload accuracy affects bearing life, valve internals where uniform sealing pressure matters, the washer face is essential.
Should I use ASME B18.2.1 or DIN 933? ASME B18.2.1 covers both inch and metric variants (ISO 4014 / 4017 are referenced); DIN 933 (full thread) and DIN 931 (partial thread) are German-pattern metric standards. Dimensions are nearly identical between DIN and ISO, specify whichever your project documentation references. For new designs, prefer ISO 4014 / 4017 (more globally portable).
What's the typical lead time for Incoloy 925 hex cap screws? Standard sizes (M8 to M24 / 5/16" to 1"): 5–7 weeks. Larger sizes (M30 to M48 / 1-1/8" to 2"): 7–9 weeks. Custom precision tolerance (Grade A with ground body): add 2 weeks for the body-grinding operation. The bottleneck is the 18-hour age cycle plus the cap-screw precision machining.
Documentation Package
- EN 10204 3.1 manufacturer's MTC (3.2 with TPI on request)
- Heat-lot chemistry vs UNS N09925 limits
- Tensile + RA + elongation per heat / per heat-treatment lot
- 100% hardness inspection (32–35 HRC NACE band)
- Charpy at -46°C / -101°C as applicable
- Heat-treatment furnace chart-recorder traces
- Cap-screw precision dimensional check (body OD, head AF, washer-face diameter + height, point chamfer)
- Thread gauge inspection (Go / No-Go) ASME B1.3
- NACE MR0175 Table A.10 reference
- API 6A PSL level reference (TPI for PSL-4)
- Cap-screw marking: grade + heat number + standard ref + NACE stamp
Related Products
- Standard hex bolts, looser-tolerance variant for general structural use
- Heavy hex bolts, larger AF + thicker head variant
- Hex nuts, standard mating nut
- Socket head cap screws, internal-hex-drive precision variant
- Washers, companion flat / lock washers
- Full Incoloy 925 datasheet
Request a Quote
For Incoloy 925 hex cap screws with full MTC documentation:
- Email: info@torqbolt.com
- Phone: +91-22-66157017
- WhatsApp: +91-22-66157017
Specify diameter, length, thread reach (full / partial), thread series (UNC / UNF / metric), tolerance class (Grade A precision / Grade B standard), dimensional standard (ASME B18.2.1 / ISO 4014 / DIN 933), quantity, applicable standards (API 6A PSL level, NACE MR0175 stamp, NORSOK MDS A30), required MTC level (3.1 / 3.2 with TPI witness) and any coating / finish requirement.
References: ASTM B805; ASTM A193 / F2281; ASME B18.2.1 (inch hex bolt + cap screw); ISO 4014 / 4017 (metric hex bolt / screw, Grades A + B); DIN 931 / 933 (German metric hex cap screws); ASME B1.1 / B1.13M (thread series); ASME B1.3 (thread gauging); API Specification 6A Annex M; NACE MR0175 / ISO 15156-3 Table A.10; NORSOK M-630 / M-650; EN 10204; ASTM A380 / A967 (passivation); MIL-DTL-16232. Special Metals Corporation INCOLOY® alloy 925 Technical Bulletin. INCOLOY® is a registered trademark of Special Metals Corporation.
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