ASTM A194
Grade 6 / 6F
Carbon Steel Nuts
Why 6 and 6F Aren’t a Strength Decision
It’s easy to assume the letter suffix on a nut grade signals a different strength tier — that pattern holds for several ASTM A194 grades, but it genuinely doesn’t hold here. Grade 6 and Grade 6F are both quenched-and-tempered medium carbon steel, heat treated to the same mechanical property requirements, intended for the same general bolting service.
The actual difference is sulfur content, added deliberately to Grade 6F — a controlled sulfur addition improves machinability specifically for high-volume automatic screw-machine production, where cutting tool wear and cycle time genuinely matter at scale. That composition change doesn’t meaningfully affect the finished nut’s tensile or hardness properties; it changes how efficiently the nut can be machined during manufacture.
That distinction matters for how you specify, not for how the nut performs once installed — a buyer choosing between Grade 6 and 6F is really making a manufacturing-process decision on our end, not a service-condition decision on theirs, and either grade delivers the same mechanical performance in the field.
Akbar Fasteners Pvt. Ltd. exports to over 50 countries, and our Grade 6 and 6F nut range is verified by chemical composition and mechanical testing under our ISO 9001:2015 quality system.
Where This Grade Genuinely Applies
Genuine Heat-Treated Strength
Quenched-and-tempered carbon steel delivers real mechanical properties beyond as-rolled material.
Correct Choice for General Industrial Bolting
Reliable, cost-effective option where full alloy-steel strength isn’t required.
Genuine Manufacturing Efficiency With 6F
Sulfur-enhanced machinability suits high-volume automatic screw-machine production.
Verified Mechanical Properties
Batch testing confirms genuine hardness and tensile properties for both grades.
Grade 6 vs Grade 6F — Side by Side
ASTM A194 Grade 6
Standard medium carbon steel, quenched and tempered. The default choice unless high-volume automatic machining specifically calls for the free-machining variant.
Standard Manufacturing →ASTM A194 Grade 6F
Same heat-treated mechanical properties as Grade 6, with controlled sulfur added specifically to improve machinability on automatic screw machines.
High-Volume Manufacturing →Grade 6 vs Grade 6F — Quick Reference
Confirming whether high-volume automatic machining is genuinely part of your production need decides which variant to specify. This table is the quick reference we use with buyers before quoting.
| Aspect | Grade 6 | Grade 6F |
|---|---|---|
| Base Material | Medium carbon steel | Medium carbon steel, sulfur-enhanced |
| Heat Treatment | Quenched & tempered | Quenched & tempered, same requirement |
| Mechanical Properties | Standard Grade 6 requirements | Same as Grade 6 |
| Machinability | Standard | Improved for automatic screw machines |
Grade 6 / 6F Specification Details
Nominal Composition
- Carbon Medium Carbon Range
- Manganese Controlled per Grade
- Sulfur (Grade 6F Only) Controlled Addition
- Iron Balance
Typical Mechanical Range
- Hardness Per ASTM A194 Grade 6
- Condition Quenched & Tempered
- Proof Load Matched to Bolt Grade
- Grade 6F Mechanical Same as Grade 6
Fastener Types We Manufacture
- Hex Nuts Standard & Heavy Hex
- Jam Nuts Thin Profile
- Matching Bolts Compatible Carbon Steel Grades
- Custom Sizes On Request
Application Areas
Wherever heat-treated carbon steel bolting is genuinely sufficient for the service load.
General Industrial Machinery
carbon steel bolting
Structural Fabrication
bolted connections
High-Volume OEM Production
automatic screw-machine runs
General Equipment Assembly
fastening for standard loads
Automotive Component Manufacturing
with machinability requirements
Construction Equipment
for construction machinery
General Piping & Flange Bolting
and piping connections
General Heat-Treated Bolting
needing standard heat-treated strength
Standard Export Documentation
Prepared as standard practice for every Grade 6 / 6F nut shipment.
Mill Test Certificate (MTC)
Heat number, chemical composition, and mechanical property verification for every lot.
Hardness & Proof Load Report
Confirms actual hardness and proof load meet the specified grade requirement.
Certificate of Conformance
Confirms the shipment matches the purchase order grade/size specification in full.
Certificate of Origin (COO)
Confirms India as country of manufacture for destination customs purposes.
NABL Accredited Test Reports
Independent mechanical and dimensional testing available on request.
Commercial Invoice & Packing List
Itemized value, Incoterm, and detailed carton/weight breakdown for customs clearance.
Internationally Recognised Standards Coverage
Related Fastener Grades & Materials
High-Tensile Bolt Grades
Our broader guide to higher-strength grades where Grade 6/6F’s carbon steel strength isn’t sufficient.
View High-Tensile Guide →ASTM A193 B7 / B7M / B6
Our alloy steel stud bolt grade guide, typically paired with higher-strength A194 nut grades.
View ASTM A193 Guide →Military Fasteners — Nuts
Our military and federal specification nut directory, for defense and aerospace bolting needs.
View Military Nuts →Fasteners Manufacturer & Exporter to the USA
Our broader capability manufacturing to ASTM/ASME and US federal/military standards.
View USA Export Guide →Standard or High-Volume
Automatic Machining?
Tell us your production requirements — we’ll confirm whether Grade 6 or 6F genuinely fits, 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