Description
Stainless pressure-service fastener
ASTM A194 Grade 8M Heavy Hex Nuts
Factory-direct supply for flange, valve and pressure-equipment bolting. Common market configurations are available; final supply is confirmed against the complete RFQ and mating stud requirements.
Procurement specification
| Product | Heavy hex nuts for pressure-service bolting assemblies |
|---|---|
| Material specification | ASTM A194/A194M, Grade 8M; the purchase-order edition governs |
| Material family | 316-series austenitic stainless steel |
| Dimensional basis | ASME B18.2.2 inch-series heavy hex geometry where specified, or the ordered dimensional standard/drawing |
| Thread | UNC, 8UN or another ordered thread series and class of fit compatible with the mating stud |
| Supply form | Nuts supplied separately or as an order-defined bolting set |
| Finish | Plain or project-specified surface condition; coating and lubricant compatibility must be confirmed before order |
| Packaging | Market-standard industrial and export packaging options, selected for quantity, handling and destination |
| Lead time | Confirmed after technical and commercial review; the fastest achievable lead time can be 7 working days |
Supply can be arranged for common market diameters and thread configurations, either as standalone nuts or as part of an order-defined bolting package. Quotations are checked item by item so the nut style, thread, mating fastener, finish, quantity, documents and packing method remain consistent with the purchaser’s line list or bill of materials.
The product photograph shows representative stainless steel nuts. Grade 8M identity, heat/lot traceability and conformance are established by marking and order documentation, not by appearance.
What the order must define
Diameter and thread
State the nominal diameter, thread series, pitch and required class of fit. The nut thread must match the ordered stud or bolt.
Nut geometry
Specify heavy hex and the dimensional standard. A generic “hex nut” description is not enough for pressure-service procurement.
Mating bolting
Identify the stud or bolt grade and condition. Grade 8M is commonly considered with B8M stainless bolting, but the governing design selects the final combination.
Inspection scope
List material certificates, proof-load or hardness requirements, dimensional reports, PMI or third-party inspection when required.
Grade 8M selection boundary
ASTM A194/A194M covers carbon, alloy and stainless steel nuts intended for bolts used in high-pressure or high-temperature service, or both. Grade 8M identifies the 316-series stainless nut grade within that specification. ASTM A194 controls material, mechanical, heat-treatment, marking and test requirements; it does not replace the separate dimensional and thread standards stated by the buyer.
Grade 8M and Grade 8 are not interchangeable descriptions. Grade 8 is associated with a 304-series stainless composition, while Grade 8M is associated with a 316-series composition. The letter “M” is part of the ASTM grade designation and must be retained in the RFQ, purchase order, marking review and certificate review.
Thread, fit and coating checks
Thread compatibility is a purchase-critical item. Large inch-series pressure bolting may use UNC or 8UN threads depending on diameter and project rules. Metric projects require the complete metric designation and tolerance class. A nut with the correct nominal diameter but the wrong pitch or fit cannot be accepted as a substitute.
Any coating, anti-seize compound or lubricant can change thread fit and installation behavior. Stainless bolting can also be vulnerable to galling if material pairing, surface condition and assembly method are not properly controlled. State the required finish and assembly practice so clearance, lubrication and torque/tension procedures can be reviewed together.
Inspection and documentation options
Identity
Review grade and manufacturer markings against the purchase specification. Special marking requirements must be stated before production.
Dimensions
Check width across flats, thickness, bearing face and thread geometry against the ordered standard and size.
Mechanical verification
Testing and acceptance follow the ordered ASTM edition and any agreed supplementary requirements; results are lot-specific.
Documents
Material certificates, dimensional reports and additional inspection records can be provided when included and confirmed in the order.
Typical uses
Grade 8M heavy hex nuts are commonly specified for stainless pressure bolting on pipe flanges, valves, pressure vessels, heat exchangers and related equipment. Typical industries include chemical processing, water treatment, food and beverage equipment, energy systems and general process piping where the engineering specification selects 316-series stainless bolting.
Actual service suitability remains project-specific. Temperature, corrosion environment, gasket type, joint design, installation method and mating fastener properties must be reviewed before the bolting set is approved.
RFQ checklist
- ASTM A194/A194M edition and Grade 8M
- Nominal diameter and quantity
- Thread series, pitch and class of fit
- Heavy hex dimensional standard or approved drawing
- Mating stud or bolt specification, grade and condition
- Plain finish, coating, lubricant or cleanliness requirements
- Marking, traceability and packaging instructions
- Material certificate, testing, PMI, dimensional report or third-party inspection scope
- Required delivery destination and schedule
Send your Grade 8M nut requirements
Include the diameter, thread, mating stud, quantity, finish and document scope. We will confirm the supply configuration, packaging and achievable delivery.
Frequently asked questions
What material is ASTM A194 Grade 8M?
Grade 8M is the 316-series austenitic stainless steel nut grade within ASTM A194/A194M. The ordered standard edition and lot documentation govern the supplied product.
What stud bolt is commonly paired with Grade 8M nuts?
ASTM A193 B8M bolting is a common pairing when specified by the design. The correct class, thread, size and service requirements must still be confirmed by the project specification.
Are Grade 8 and Grade 8M the same?
No. Grade 8 is associated with 304-series stainless steel, while Grade 8M is associated with 316-series stainless steel. They should not be substituted without engineering and purchaser approval.
How should Grade 8M nuts be ordered?
Specify the ASTM edition, diameter, thread series and fit, heavy hex dimensional standard, mating fastener, finish, quantity, marking and required documents.
Can the nuts be supplied with certificates?
Order-specific material certificates and agreed inspection records can be provided. State the required document type and inspection scope in the RFQ for confirmation.
