Most delays on bolting orders come from enquiries that leave something out: a stud with no length, a bolt with no thread class, a grade with no matching nut. This page gives a field-by-field template for a complete bolt, stud and nut RFQ, and explains why each field matters. Copy the table into your enquiry, or use it to check a purchase requisition before it goes out.
The Fields a Complete Fastener RFQ Needs
| Field | What to state | Example |
|---|---|---|
| Item type | Hex bolt, heavy hex bolt, stud bolt (fully threaded), tap-end stud, nut, washer, screw, threaded rod | Stud bolt, fully threaded |
| Material specification and grade | The standard and grade for each component, including class where the standard has classes | ASTM A193 B7 studs |
| Nut grade | Matching nut specification and grade, and number of nuts per stud | 2 × ASTM A194 2H heavy hex nuts |
| Washers | Type, standard and material, if required | ASTM F436 hardened washers |
| Diameter and thread | Nominal diameter, thread series and pitch, and thread class / tolerance | 7/8"-9 UNC-2A, or M24 × 3 6g |
| Length | Overall length, and how it is measured for studs (end-to-end, or first-thread to first-thread) | 190 mm end-to-end |
| Dimensional standard | Head / nut dimensions and stud tolerances | ASME B18.2.1 / B18.2.2; ASME B16.5 stud lengths |
| Coating or finish | Plain, hot-dip galvanised, zinc-nickel, PTFE / fluoropolymer, phosphate; thickness and colour | PTFE coated, blue |
| Quantity | Per size, with any spares | 120 sets + 5% |
| Testing and documents | Certificate type, supplementary tests, hardness limits, third-party inspection | EN 10204 3.1; NACE MR0175 hardness |
| Marking and packing | Grade and manufacturer marking, packing per size, labels | Packed per size with heat number on label |
Material Grade: Name Each Component
A bolting assembly has several parts, and each needs its own grade. "B7 bolts" does not tell the supplier which nut to supply. For pressure bolting, the stud grade is set by ASTM A193 (high temperature) or ASTM A320 (low temperature), and the nut grade by ASTM A194. Common pairs are A193 B7 studs with A194 2H nuts, A320 L7 studs with A194 grade 4 or 7 nuts, and A193 B8 / B8M stainless studs with A194 grade 8 / 8M nuts. Where a stainless grade has strain-hardened classes (Class 1 or Class 2), state which one.
Thread, Diameter and Length
- Thread series: inch threads are usually UNC for smaller sizes and 8-UN for 1" and larger in pressure bolting; metric threads are specified by pitch (M24 × 3).
- Thread class: 2A / 2B is normal for inch fasteners; 6g / 6H for metric. Coated fasteners may need allowance for coating thickness.
- Stud length: say how the length is measured. Flange stud lengths in ASME B16.5 tables do not include point heights, so confirm the convention with your supplier.
Metric and Imperial Drawings: Quotation Mismatch Checks
| Check | Imperial (inch) | Metric |
|---|---|---|
| Diameter | Fractional inch, e.g. 7/8" | Millimetres, e.g. M24 |
| Thread pitch | Threads per inch, e.g. 9 UNC or 8UN | Pitch in mm, e.g. 3.0 (coarse) or 2.0 (fine) |
| Length | Inches; for studs state overall or first-thread-to-first-thread | Millimetres; confirm the same measurement basis |
| Dimensional standard | ASME B18.2.1 / B18.2.2, B1.1 threads | ISO 4014/4017, ISO 4032, ISO 261/262 threads |
| Strength grade | ASTM grade, e.g. A193 B7 | Property class, e.g. 8.8 or 10.9, or EN/ISO material |
Inch and metric fasteners of similar size are not interchangeable – a 1" stud and an M24 or M25 nut will not fit properly even if they appear to start. If a drawing mixes systems, or a quotation converts sizes without saying so, ask for every line to be confirmed in the units of the drawing before ordering.
Coatings
Coatings change the order in three ways: they affect thread fit, they can affect hardness or embrittlement for high-strength grades, and they add lead time. State the coating type, thickness and colour, and whether the nuts must be tapped oversize to suit hot-dip galvanising. If the bolting is for sour service, check that the coating process does not conflict with the hardness requirements.
What the Purchase Order Should Say About Coating
| Coating | Commonly referenced standard | What to state on the order |
|---|---|---|
| Hot-dip galvanising | ASTM F2329 or ASTM A153 Class C | Minimum coating thickness; nuts tapped oversize after galvanising (and the oversize allowance); whether threads are to be cleaned after coating |
| Zinc electroplating | ASTM F1941 (inch) or ISO 4042 (metric) | Coating thickness class and passivate colour; hydrogen embrittlement relief baking for high-strength grades |
| Zinc flake (non-electrolytic) | ASTM F1136 or ISO 10683 | Coating grade or salt-spray requirement, top coat and colour |
| PTFE / fluoropolymer | Usually the buyer’s or coating supplier’s specification | Base coat (for example zinc or phosphate), total thickness, colour, and that thread fit is checked after coating |
| Phosphate and oil | Buyer’s or industry specification | Phosphate type and oil, for short-term corrosion protection |
Thread allowance: thick coatings take up thread clearance. Agree whether the bolt threads are undercut before coating or the nut threads tapped oversize after coating, and check the fit with a gauge or a sample nut before the full batch is released.
Documents to request: coating thickness readings per batch, adhesion or salt-spray test results if your specification calls for them, and confirmation that the coating process does not affect the material certificate (for example baking after plating on high-strength bolts).
Testing and Documents
- EN 10204 3.1 certificate (or 3.2 with the named inspection agency)
- Supplementary requirements from the material standard, such as impact tests for A320 grades
- Hardness limits for sour service (NACE MR0175 / ISO 15156) where applicable
- PMI, proof load or dimensional inspection reports if needed
For how to check the certificate when the fasteners arrive, see our guide on reading an EN 10204 3.1 certificate.
Before You Send the RFQ
- Every line has a grade for every component (stud, nut, washer)
- Every size has a diameter, thread and length
- The length convention is stated for studs
- Coating and documents are written on the enquiry, not assumed
Browse our fasteners, including ASTM A193 B7 and A194 2H bolting, or send your completed template to our team.
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