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 Nuts (UNS N09925)
Standard hex nut companion ASME B18.2.2 / ISO 4032 — for general fastener service
Incoloy 925 hex nuts (UNS N09925) are the standard hex companion to hex bolts and hex cap screws in general fastening applications. Per ASME B18.2.2 (inch series) or ISO 4032 (metric series), the standard hex nut has a height equal to ~7/8 the bolt diameter and an across-flats (AF) dimension matched to the standard hex bolt, smaller than the heavy hex nut companion to high-load stud bolts. Standard hex nuts are appropriate for joints loaded below ~50% of bolt yield strength, where the thinner thread engagement is sufficient to develop the working-load preload. For high-load API 6A wellhead, Christmas tree and pressure-vessel bolting, the heavy hex nut is the engineering default. TorqBolt manufactures Incoloy 925 hex nuts in M3 to M64 (1/8" to 4") thread 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 nuts? Email info@torqbolt.com with thread size, thread series (UNC / UNF / metric), variant (standard / jam / slotted / castle), quantity, applicable standards (NACE MR0175 stamp). WhatsApp +91-22-66157017.
Hex Nut Variants Manufactured
| Variant | Description | Standard | Use |
|---|---|---|---|
| Standard hex nut | Six-sided nut, height ~7/8 D, chamfered both ends | ASME B18.2.2 / ISO 4032 | General fastening, hex bolt + screw service |
| Hex jam nut (thin nut) | Half-height standard hex nut (~1/2 D); used as locking nut over a full nut | ASME B18.2.2 / ISO 4035 | Vibration-loosening prevention; secondary lock |
| Hex slotted nut | Standard nut with 6 slots cut into top face for cotter pin | ASME B18.2.2 (slotted hex) | Locked-position joints requiring positive mechanical retention |
| Hex castle nut | Crown of points with cut slots between, cotter-pin retention pattern | ASME B18.2.2 / ISO 7035 | Wheel hub, axle, drilled-shank-bolt joints |
| Hex flange nut | Integral flange (washer face) under hex; eliminates separate washer | ASME B18.2.2 / ISO 4161 | Sheet-metal joining, vibration-prone joints, low-clearance use |
| Hex coupling nut | Long hex nut joining two threaded rods end-to-end | ASME B18.2.2 | Threaded rod extension joints |
Standard Size Range & Dimensions
| Thread Size | UNC (inch) | UNF (inch) | Metric Coarse | Standard AF | Standard Nut Height | Jam Nut Height |
|---|---|---|---|---|---|---|
| 1/8" / M3 | UNC 40 | UNF 48 | M3 × 0.5 | 5/16" / 5.5 mm | 3/32" / 2.4 mm | 1/16" / 1.8 mm |
| 1/4" / M6 | UNC 20 | UNF 28 | M6 × 1.0 | 7/16" / 10 mm | 7/32" / 5 mm | 5/32" / 3.2 mm |
| 5/16" / M8 | UNC 18 | UNF 24 | M8 × 1.25 | 1/2" / 13 mm | 17/64" / 6.5 mm | 3/16" / 4 mm |
| 3/8" / M10 | UNC 16 | UNF 24 | M10 × 1.5 | 9/16" / 17 mm | 21/64" / 8 mm | 1/4" / 5 mm |
| 7/16" / M12 | UNC 14 | UNF 20 | M12 × 1.75 | 5/8" / 19 mm | 3/8" / 10 mm | 9/32" / 6 mm |
| 1/2" / M14 | UNC 13 | UNF 20 | M14 × 2.0 | 3/4" / 22 mm | 7/16" / 11 mm | 5/16" / 7 mm |
| 9/16" / M16 | UNC 12 | UNF 18 | M16 × 2.0 | 13/16" / 24 mm | 31/64" / 13 mm | 23/64" / 8 mm |
| 5/8" / M18 | UNC 11 | UNF 18 | M18 × 2.5 | 15/16" / 27 mm | 35/64" / 15 mm | 3/8" / 9 mm |
| 3/4" / M20 | UNC 10 | UNF 16 | M20 × 2.5 | 1-1/8" / 30 mm | 41/64" / 16 mm | 27/64" / 10 mm |
| 7/8" / M22 | UNC 9 | UNF 14 | M22 × 2.5 | 1-5/16" / 32 mm | 3/4" / 18 mm | 31/64" / 11 mm |
| 1" / M24 | UNC 8 | UNF 12 | M24 × 3.0 | 1-1/2" / 36 mm | 55/64" / 21 mm | 35/64" / 13 mm |
| 1-1/8" / M30 | UNC 7 | UNF 12 | M30 × 3.5 | 1-11/16" / 46 mm | 31/32" / 25 mm | 5/8" / 15 mm |
| 1-1/4" / M33 | UNC 7 | UNF 12 | M33 × 3.5 | 1-7/8" / 50 mm | 1-1/16" / 28 mm | 3/4" / 18 mm |
| 1-3/8" / M36 | UNC 6 | UNF 12 | M36 × 4.0 | 2-1/16" / 55 mm | 1-11/64" / 31 mm | 13/16" / 21 mm |
| 1-1/2" / M39 | UNC 6 | UNF 12 | M39 × 4.0 | 2-1/4" / 60 mm | 1-9/32" / 34 mm | 7/8" / 22 mm |
Above 1-1/2" diameter: standard hex nut becomes impractical for most service due to insufficient thread engagement. Use heavy hex nuts for diameters above 1-1/2" / M39 unless the joint is specifically low-load.
Mechanical Property Requirements
| Property | Aged Condition |
|---|---|
| Proof Load | Matched to 110 ksi YS bolt grade per ASTM A194 Table 3 |
| Parent Tensile Strength | 165 ksi (1140 MPa) min |
| 0.2% Yield Strength | 110 ksi (760 MPa) min |
| Hardness | 32–35 HRC (NACE sour-service cap) |
| Charpy V-notch at -46°C (sample) | 40 J min |
Sample proof-load test per heat-treatment lot per ASTM A194 Table 3. The standard hex nut height (~7/8 D) is sufficient to develop full 100% bolt-yield preload only on bolts of 110 ksi YS or below; for higher-grade bolts (Inconel 718 at 150 ksi YS), use heavy hex nuts to prevent thread strip-out.
Applicable Standards
- ASTM B805, UNS N09925 forging stock (input)
- ASME B18.2.2, Square and Hex Nuts (inch dimensional)
- ISO 4032, Hexagon Regular Nuts (metric Style 1)
- ISO 4033, Hexagon Regular Nuts (metric Style 2, thicker)
- ISO 4035, Hexagon Thin Nuts (chamfered, metric jam nut)
- ISO 4161, Hexagon Nuts with Flange (metric flange nut)
- ISO 7035, Hexagon Castle Nuts
- DIN 934, Hexagon Nut (German equivalent of ISO 4032)
- ASTM A194, Carbon and Alloy Steel Nuts (proof-load reference)
- API 6A, Wellhead and Tree Equipment
- NACE MR0175 / ISO 15156-3, sour-service Table A.10
- 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 | Sample MT |
| PSL-3 | 10,000–15,000 psi | 27 J at -29°C | 100% MT or PT |
| PSL-3G | 10,000–15,000 psi gas | 27 J at -46°C / -101°C | 100% MT + grain size |
| PSL-4 | 15,000–20,000 psi | 40 J at -46°C | 100% MT + 100% PT + TPI witness |
Manufacturing Sequence
- Bar input: Incoloy 925 hex bar (preferred for nut blanks, saves machining the hex profile) or round bar (for small quantities) per ASTM B805 in annealed condition.
- Blank cutting: Hex bar cold-saw or shear-cut to nut height + finishing allowance. Both faces machined flat and parallel.
- Chamfering: Both top and bottom faces chamfered to 30° ASME B18.2.2 / ISO 4032 to remove sharp edges and ease nut starting on bolt thread.
- Through-hole: Pilot hole drilled centrally, then bored to thread minor diameter.
- Internal thread tapping: Cut internal thread in solution-annealed condition. Rotary tap with controlled cutting speed and high-pressure coolant flush to avoid chip jamming in nickel-alloy material.
- Solution anneal + age cycle: Per heat-treatment specification. Standard hex nuts age uniformly due to thinner section, less risk of furnace-loading-related variability than heavy hex.
- Final inspection: AF + corner-to-corner dimensional check; nut height + chamfer angle verification; internal thread gauging Go / No-Go ASME B1.3; 100% Rockwell hardness; sample proof-load per ASTM A194.
- Marking: Each nut stamped on one face with grade designation + heat number + manufacturer ID + NACE stamp (sour orders).
Companion Components
- Incoloy 925 hex bolts, primary mating fastener
- Hex cap screws, precision-tolerance mating bolt
- Flat washers, load distribution under nut bearing face
- Spring washers / lock washers, vibration retention
- Cotter pins, mating retention for slotted / castle hex nuts
- Thread compound, sulphur-free, copper-free anti-seize per API RP 7A1
Application Examples
- General fastening on Incoloy 925 hex bolt joints: Brackets, supports, mounting hardware
- Pump baseplate bolting: Standard hex nut where the joint is not full-preload critical
- Pipe support bolting: Sour-service piping clamps, hangers, anchors
- Instrument enclosure mounting: Sensor housings, junction boxes in sour atmosphere
- Threaded-rod extension joints: Coupling nut joining two threaded rods (rare; usually use a single longer rod)
- Vibration-prone joints (jam-nut configuration): Standard nut + jam nut to lock against rotation
- Slotted / castle nut applications: Wheel hubs, axle ends, drilled-shank pins requiring positive lock
- Light-duty subsea components: Where weight savings vs heavy hex matters
Standard Coatings & Finishes
- Bare (passivated): Per ASTM A380 / A967, standard sour-service finish
- PTFE coating: Xylan 1424 / 1070, reduces friction during make-up
- 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 standard hex nut and a heavy hex nut? Standard hex nut (ASME B18.2.2) has height ~7/8 D and AF matched to ASME B18.2.1 standard hex bolts. Heavy hex nut (ASME B18.2.6) has height ~equal to D and larger AF matched to heavy hex / API 6A bolting. Use standard for general fastener service; heavy hex for high-preload pressure and structural joints.
What's the difference between ISO 4032 (Style 1) and ISO 4033 (Style 2) metric hex nuts? Style 1 is the standard regular thickness (~0.8 D); Style 2 is thicker (~0.9 D) for higher-strength applications. ISO 4033 Style 2 is roughly equivalent to ASME B18.2.6 heavy hex but with metric series dimensioning. Specify which Style at RFQ stage.
When should I use a jam nut? A jam nut is a thinner (half-height) hex nut used as a secondary lock against vibration loosening. The jam nut is tightened first, then the full nut is tightened against it, the two nuts wedge against each other on the thread, making rotation difficult. Used in vibration-prone applications where lock-washers are inadequate or banned by code.
Why no nuts above 1-1/2" / M39 in standard hex? Above this size, the standard hex nut height becomes too thin to develop full-strength thread engagement on a 165 ksi UTS Incoloy 925 stud. The thread strips out before the bolt yields. Use heavy hex nuts for diameters above 1-1/2", the heavy series provides sufficient thread engagement at large diameters.
What's the typical lead time for Incoloy 925 hex nuts? Standard sizes (M6 to M24 / 1/4" to 1"): 4–6 weeks ex-stock or 6–8 weeks new-melt. Larger sizes (M30 to M39 / 1-1/8" to 1-1/2"): 8–10 weeks. Specialty variants (jam, slotted, castle, coupling): add 2–3 weeks for the additional machining operation.
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
- Sample proof-load test per ASTM A194 Table 3
- 100% hardness inspection (32–35 HRC NACE band)
- Sample Charpy at -46°C as applicable
- Heat-treatment furnace chart-recorder traces
- Nut dimensional check (AF, height, chamfer angle) ASME B18.2.2 / ISO 4032
- Internal thread gauge Go / No-Go ASME B1.3
- NACE MR0175 Table A.10 reference
- Nut marking: grade + heat number + manufacturer ID + NACE stamp
Related Products
- Heavy hex nuts, thicker / wider companion for high-load joints
- Hex bolts, primary mating fastener
- Hex cap screws, precision-tolerance mating screw
- Washers, flat / lock companions
- Threaded rods, with coupling nut for extension joints
- Full Incoloy 925 datasheet
Request a Quote
For Incoloy 925 hex nuts with full MTC documentation:
- Email: info@torqbolt.com
- Phone: +91-22-66157017
- WhatsApp: +91-22-66157017
Specify thread size, thread series (UNC / UNF / metric), variant (standard / jam / slotted / castle / coupling / flange), dimensional standard (ASME B18.2.2 inch / ISO 4032 metric / DIN 934), 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; ASME B18.2.2 (square + hex nuts); ISO 4032 / 4033 / 4035 / 4161 / 7035 (metric hex nut variants); DIN 934 (German hex nut); ASTM A194 (nut proof-load); 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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