Imperial-thread fasteners machined to order in nickel aluminium bronze (CuAl10Ni5Fe4 — CW307G / CA104) and aluminium silicon bronze (CuAl6Si2Fe — CW301G / CA107). UNC and UNF (Unified) to ASME B1.1 thread form, with hex dimensions to ASME B18.2.1 (hex cap screws / finished hex bolts) and B18.2.2 (finished hex nuts) where specified, or to the legacy UK standards BS 1768 (precision, normal series) and BS 1769 (heavy series) — each covering bolts, screws and nuts, and not direct equivalents of the ASME standards; BSW and BSF (Whitworth) to BS 84 with hex dimensions to BS 1083, which applies to non-ferrous fasteners; BA for small screws. 1/4" to 2" nominal, smaller and larger subject to manufacturing review. Supplied with material certification and, where specified, to NES 833 / DEF STAN 02-833 for NAB, NES 834 / DEF STAN 02-834 Pt 2 (superseded by 02-879 Pt 2 Annex D, Sept 2011) for SAB, and the DEF STAN 02-862 Part 2 manufacturing route.
Imperial threads still turn up on Royal Navy legacy platforms and refit work, on US-origin machinery and valves, and on equipment designed before metrication. Drawings from the 1960s–80s often carry Whitworth or Unified threads with no metric equivalent — send the drawing as it is and we'll make to it. No minimum order quantity.
| Series | Standard | Description | Typical use |
|---|---|---|---|
| UNC (Unified Coarse) | ASME B1.1 | The standard inch coarse thread, 60° form. Same tpi as BSW at every size in this range except 1/2" (13 against BSW's 12), but a different thread form; not interchangeable as a specification | US-origin equipment, most general imperial fastening |
| UNF (Unified Fine) | ASME B1.1 | Inch fine thread; higher tensile area for a given diameter | Valves, instrumentation, higher-load joints |
| BSW (British Standard Whitworth) | BS 84 | Legacy UK coarse thread, 55° form | Pre-metrication UK naval and industrial equipment |
| BSF (British Standard Fine) | BS 84 | Legacy UK fine thread, 55° form | Pre-metrication UK equipment |
| BA (British Association) | BS 93 | Small-diameter thread series; BS 93 runs 0BA–16BA, with 0BA (6.0 mm) to 10BA (1.7 mm) in common use; smallest sizes subject to manufacturing review | Instruments, electrical fittings, small naval equipment |
Standard-series sizes 1/4" to 2". Hex across-flats per ASME B18.2.1 hex cap screws (finished hex bolts) and B18.2.2 finished hex nuts, regular series.
| Nominal | UNC tpi | UNF tpi | Bolt head AF (in) | Nut AF (in) |
|---|---|---|---|---|
| 1/4 | 20 | 28 | 7/16 | 7/16 |
| 5/16 | 18 | 24 | 1/2 | 1/2 |
| 3/8 | 16 | 24 | 9/16 | 9/16 |
| 7/16 | 14 | 20 | 5/8 | 11/16 |
| 1/2 | 13 | 20 | 3/4 | 3/4 |
| 9/16 | 12 | 18 | 13/16 | 7/8 |
| 5/8 | 11 | 18 | 15/16 | 15/16 |
| 3/4 | 10 | 16 | 1-1/8 | 1-1/8 |
| 7/8 | 9 | 14 | 1-5/16 | 1-5/16 |
| 1 | 8 | 12 | 1-1/2 | 1-1/2 |
| 1-1/8 | 7 | 12 | 1-11/16 | 1-11/16 |
| 1-1/4 | 7 | 12 | 1-7/8 | 1-7/8 |
| 1-3/8 | 6 | 12 | 2-1/16 | 2-1/16 |
| 1-1/2 | 6 | 12 | 2-1/4 | 2-1/4 |
| 1-3/4 | 5 | — | 2-5/8 | 2-5/8 |
| 2 | 4-1/2 | — | 3 | 3 |
Regular hex series shown. Heavy hex nuts, usual on flange studbolts, are larger — say which the drawing calls for. BSW and BSF hex sizes to BS 1083 differ from the Unified sizes above; where the drawing is Whitworth we use the BS 1083 across-flats. Unified threads: class 2A external / 2B internal unless the drawing specifies otherwise; BSW/BSF tolerances per BS 84 and the drawing.
All imperial forms — hex head bolts and hex head setscrews, hex nuts, studs and studbolts, socket screws, machine screws, washers — to drawing.
CuAl10Ni5Fe4. The higher-strength alloy, with excellent seawater, erosion and cavitation resistance; commonly specified for structural and immersed fastenings. Naval material standard NES 833 / DEF STAN 02-833 Part 2. Relative magnetic permeability typically around 1.4–1.5. Full data, designations and cross-references on the NAB material page.
CuAl6Si2Fe. Good machinability, ductile, and formulated for controlled low magnetic permeability — relative magnetic permeability not exceeding 1.05 (DEF STAN 02-879 Part 2 Annex D, D.2.8; batch-tested to D.4.5) — used for mine countermeasures vessels and other naval low-signature applications. Tighter permeability limits are a drawing or contract requirement and are handled at enquiry stage. Naval material standard NES 834 / DEF STAN 02-834 Part 2, subsequently incorporated into DEF STAN 02-879 Part 2 Annex D. Full data on the SAB material page.
Source-material certification supplied as standard, with traceability to the bar heat maintained through manufacture. Where the drawing calls for DEF STAN 02-862 Part 2, threaded fasteners are machined from bar with machined threads and post-machining stress relief per clause 8.2.4 (NAB) or 8.2.5 (SAB), with heat treatment and stress relief records supplied where required by the drawing, specification or purchase order; washers follow the separate washer route with no further heat treatment. Unified threads on 02-862 orders follow clause 8.3.2 (UNC or UNF to 1", 8 tpi above 1", 2A / 2B) unless the drawing specifies otherwise. Marking, EN 10204 3.1 certification, dimensional inspection reports and CoC as required by the order; EN 10204 3.2 where agreed in advance and supported by the material source and inspection arrangements.
The drawing and specification govern. Alloy designations above are cross-references, not statements of equivalence.
UNC, UNF, BSW, BSF, BA — bolts, nuts, studs, screws — send the drawing as it is and we'll quote within 24 hours.
Send us your drawing or spec reference and we'll come back with a price and lead time. No minimum order quantity.