ASTM A194
Grade 2HM
Metric Heavy Hex Nuts
Grade 2H vs Grade 2HM — The Actual Difference
Grade 2HM is not a different material class from Grade 2H — it’s the identical through-hardened carbon steel specification, at the identical heavy-hex dimensional proportions, differing only in thread and sizing convention. Grade 2H is sized to standard inch threading. Grade 2HM is sized to metric threading, for projects specified in metric units.
The heavy hex profile itself is a genuine, deliberate design feature shared by both grades — a larger across-flats dimension and increased thickness compared to standard hex nuts, providing greater bearing surface area against the flange or gasket face and more wrenching torque capacity. That’s particularly valuable in high-pressure flanged connections where the nut needs to distribute clamping load evenly and withstand higher installation torque without deformation.
Grade 2HM is commonly specified in combination with NACE MR0175/MR0103 requirements for sour service piping using metric-sized studs — pairing metric heavy hex geometry with the hardness controls that sour service demands, matched typically with A193 Grade B7M or A320 Grade L7M metric stud bolts depending on whether temperature or sour service is the primary driver.
Akbar Fasteners Pvt. Ltd. exports to over 50 countries, and we manufacture Grade 2HM to order — including NACE-compliant testing where required — verified under our ISO 9001:2015 quality system. Please confirm your sizing convention and whether NACE compliance is required when ordering.
Where This Grade Genuinely Applies
Genuine Bearing Surface Advantage
Heavy hex dimensions distribute clamping load more evenly across flange and gasket faces.
Correct Sizing for Metric Projects
Matched to metric thread standards for drawings and project specifications in metric units.
NACE Compliance Available
Manufactured and hardness-tested to MR0175/MR0103 requirements when specified for sour service.
Verified Mechanical Properties
Batch hardness and proof load testing confirms consistent through-hardened strength for every lot.
Choosing Between Related Carbon & Alloy Steel Grades
Grade 2H
Identical through-hardened carbon steel and heavy hex profile, sized to inch threading instead of metric.
View Grade 2H →Grade 2HM (This Page)
Same through-hardened carbon steel, metric threading, for metric-specified project drawings.
You Are HereGrade 7M
Our alloy steel NACE-compliant grade, for sour service where alloy content is specifically required.
View Grade 7M →Grade 2H vs Grade 2HM — Quick Reference
Confirming the sizing convention before ordering avoids a genuinely common and avoidable thread-mismatch error. This table is the quick reference we use with buyers before quoting.
| Aspect | Grade 2H (Inch) | Grade 2HM (Metric) |
|---|---|---|
| Base Material | Carbon steel | Identical composition |
| Hardness/Condition | Through-hardened | Identical treatment |
| Profile | Heavy hex | Identical heavy hex proportions |
| Thread Sizing | Inch, per ASME B18.2.2 | Metric, per metric dimensional standard |
Grade 2HM Specification Details
Nominal Composition
- Base Type Medium Carbon Steel
- Heat Treatment Through-Hardened
- Alloying Elements Not Required
- Hardness Range Elevated, Per ASTM A194 Grade 2HM
Typical Mechanical Range
- Profile Heavy Hex
- Proof Load Per ASTM A194 Grade 2HM
- NACE Compliance Available on Request
- Matching Bolt Grade ASTM A193 B7M / A320 L7M
Fastener Types We Manufacture
- Heavy Hex Nuts Metric Sizing
- Jam Nuts Thin Profile, On Request
- Coating Options Zinc, Black Oxide, Plain
- Custom Sizes On Request
Application Areas
Wherever high-pressure flanged connections are specified to metric standards, with or without NACE sour service requirements.
Metric-Specified Piping & Flanges
connections, metric drawings
International Project Piping Systems
outside inch-based markets
Metric Sour Service Piping
flange bolting
Pressure Vessel Flange Bolting
needing greater bearing area
Standard Export Documentation
Prepared as standard practice for every Grade 2HM nut shipment.
Mill Test Certificate (MTC)
Heat number, chemical composition, and mechanical property verification for every lot.
Hardness Test Report
Confirms through-hardened hardness meets the specified Grade 2HM requirement, including NACE limits if applicable.
Certificate of Conformance
Confirms the shipment matches the purchase order grade/sizing specification in full.
Certificate of Origin (COO)
Confirms India as country of manufacture for destination customs purposes.
Dimensional Inspection Report
Confirms correct metric thread sizing and heavy hex proportions.
Commercial Invoice & Packing List
Itemized value, Incoterm, and detailed carton/weight breakdown for customs clearance.
Internationally Recognised Standards Coverage
Related Fastener Grades & Materials
ASTM A194 Grade 2H
Our identical through-hardened, heavy hex grade in inch sizing, for imperial-unit projects.
View Grade 2H →ASTM A194 Grade 7M
Our alloy steel NACE-compliant grade, an alternative where alloy content is specifically required.
View Grade 7M →ASTM A194 Grade 2 / 2M
Our standard quenched-and-tempered grade, for joints not requiring the heavy hex profile.
View Grade 2 / 2M →Stainless Steel Fasteners Manufacturer India
Our broader fastener manufacturing capability across all major carbon, alloy, and stainless grades.
View SS Manufacturer Guide →Metric Heavy Hex,
NACE Compliant on Request
Tell us your sizing requirements and whether NACE compliance is needed — we’ll confirm manufacturability and quote with full documentation. Akbar Fasteners Pvt. Ltd. responds within 24 hours.
Sales: +91 724 0000 733 · Support: +91 800 9315 333 · sales@akbarfasteners.in