How fasteners are made
Most bolts and screws are cold forged: wire rod is drawn to size, cut, and its head formed in a multi-station header. Threads are rolled, not cut, so the grain follows the thread form. Larger or special bolts are hot forged and their threads rolled or cut afterwards. Nuts are formed or forged and then tapped. Each step adds a risk that a sample cannot reveal on its own: a worn heading die, a rolling die set out of adjustment, a tap past its life.
Strength comes from steel grade and heat treatment. Property class 8.8 and above are hardened and tempered, usually in mesh-belt furnaces with controlled atmosphere to avoid decarburising the surface. Finishing follows: zinc electroplating with passivation, zinc-nickel, hot-dip galvanising, zinc flake coating or black oxide. Electroplating high-strength parts brings a risk of hydrogen embrittlement, in which a bolt cracks hours or days after tightening.
India exported US$864.4 million of screws, bolts, nuts and washers of iron or steel (HS 7318) in FY2025-26, according to Department of Commerce TradeStat; the figure is provisional. We do not name fastener towns here because we have not confirmed one in an official source.
What we check on fasteners
| Check | How it is checked | What fails |
|---|---|---|
| Head marking | Property class (for example 8.8, 10.9) and maker's mark read on every sampled piece; inch bolts checked for SAE J429 radial lines or ASTM grade marks | Missing mark; class or grade different from the order; no maker's mark where required |
| Threads | Go and no-go ring and plug gauges for the ordered fit (for example 6g and 6H, or UNC 2A and 2B), checked after coating; gauge calibration certificates checked | No-go gauge enters; go gauge does not run fully |
| Dimensions | Length, head height, width across flats, thread length, socket depth and washer face measured against the product standard or drawing | Short thread length; undersize across flats; shallow socket |
| Hardness | Witnessed on the factory's calibrated tester, on pieces we pick from different boxes and lots | Outside the property class range |
| Proof load and wedge tensile | Full-size bolts tested on the factory's tensile machine in our presence, to the loads ISO 898-1 sets for the size and class; machine calibration checked | Permanent stretch after proof load; head breaks off in the wedge test |
| Coating | Thickness by magnetic gauge on sampled parts; appearance, colour and coverage; salt-spray results from the lab report for the lot | Thin or patchy coating; white rust in boxes; salt-spray report for another lot |
| Embrittlement relief | Baking records for electroplated parts of high property classes: time from plating to oven, temperature and duration, matched to lot numbers | No baking record; long delay before baking |
| Lot integrity and count | Boxes opened at random for mixed sizes, classes or finishes; count per box weighed or counted; labels checked | Mixed parts; short count; label for another lot |
ISO 898-1, the Fastener Quality Act and CBAM
ISO 898-1:2013 sets the mechanical and physical properties of bolts, screws and studs of carbon and alloy steel, tested at 10 °C to 35 °C, by property class. The first number of a class gives the nominal tensile strength in hundreds of MPa; the second gives the ratio of yield to tensile strength, so 8.8 means about 800 MPa tensile and 640 MPa yield. Nuts have their own classes under ISO 898-2:2022, and the nut class must match the bolt. ISO 3269 sets an acceptance-inspection procedure for fasteners that some buyers prefer to general AQL tables.
US Fastener Quality Act. The Act covers threaded metal screws, nuts, bolts and studs of 6 mm or ¼ inch nominal diameter and larger that are through-hardened, or represented as meeting a standard that calls for it, and that carry grade identification marking, with exclusions such as parts of assemblies and fasteners made to a proprietary standard. Where the consensus standard requires a manufacturer's insignia, covered fasteners may not be sold unless they bear it and the manufacturer has recorded it, which is done on the USPTO's Fastener Insignia Register. We check that the head mark matches the maker named in your documents; checking recordation is for you or your US importer.
EU CBAM. Heading 7318 is listed in Annex I to Regulation (EU) 2023/956, and the definitive regime has applied since 1 January 2026. The EU importer needs embedded-emissions data from the producer, so ask for it with the order. Structural bolting assemblies sold in Europe also need CE or UKCA marking under the construction products rules; see UKCA and CE marking.
Common defects in fasteners
| Defect | Why it matters | Class |
|---|---|---|
| Head marked 10.9 or 8.8 but fails proof load or hardness | Joint can fail under design load | Critical |
| Plated high-strength bolts with no baking record, or cracks found | Delayed brittle fracture after installation | Critical |
| Head cracks or bursts at the head-shank fillet | Head can snap off on tightening | Critical |
| Mixed property classes in one box | A weaker bolt ends up in a critical joint | Critical |
| Threads fail go or no-go gauge | Assembly problems, stripping | Major |
| Coating below specified thickness | Early corrosion | Major |
| Maker's mark missing | Traceability lost; may block US sale of covered fasteners | Major |
| Short count, label errors | Commercial loss and confusion at receipt | Minor |
Packing, transit and your purchase order
Fasteners are heavy for their volume. Small boxes go into strong master cartons on pallets, with a weight limit per carton and per pallet; bulk parts travel in lined steel or wooden boxes. Plated parts are sensitive to condensation, so boxes should be dry and lined. The inspector checks box labels (part number, size, class, finish, lot number and count), carton and pallet weights, and that pallets are wrapped and secured in the container.
Put these in your purchase order:
- Product standard or drawing, size, length and thread fit.
- Property class or grade, maker's mark, and nut class to match.
- Coating type and thickness, salt-spray hours, and baking requirement for plated parts.
- Which tests are witnessed (hardness, proof load, wedge) and on how many pieces per lot.
- Certificate type (EN 10204 3.1 is common) and lot traceability to box labels.
- Box quantity, labels, carton and pallet weight limits.
Independent tensile, decarburisation or salt-spray tests go to an accredited lab through lab testing coordination. Book an inspection anywhere in India.
Sources
- ISO 898-1:2013, Mechanical properties of fasteners: bolts, screws and studs (Standard Norge listing)
- ISO 898-2:2022, Mechanical properties of fasteners: nuts (Standard Norge listing)
- ISO 4042:2022, Fasteners: electroplated coating systems (Standard Norge listing)
- ISO 3269:2019, Fasteners: acceptance inspection (Standard Norge listing)
- 15 U.S.C. 5402, Fastener Quality Act definitions (Cornell LII)
- 15 U.S.C. 5407, Manufacturers' insignias (Cornell LII)
- USPTO: Fastener Quality Act (FQA) and Fastener Insignia Register
- Regulation (EU) 2023/956 establishing a carbon border adjustment mechanism (EUR-Lex)
- Department of Commerce, TradeStat: commodity-wise exports (HS 7318, FY2025-26 provisional)