BS 1083 Precision Hexagon Screws, Washer Faced (BSW and BSF Threads)
BS 1083-1965 precision hexagon head screws, washer faced, B.S.W. and B.S.F. threads: threads per inch, across flats and corners, bearing washer face dw, head height and fillet radius per size — the British inch-thread heritage hex screw.
Last updated: 2026-11
Specifications
BS 1083-1965 is the heritage British standard for precision hexagon screws on the BSW (Whitworth) and BSF thread systems, and restoring or maintaining British-built plant from the era still orders against it. The collected table carries the geometry in two positionally-paired segments (the collected page labels neither — carried in source order): threads per inch ladders (20, 18, 16, 14, 12, 12, 11, 10 and the finer continuation 9 down to 4.5), across flats s max/min (0.445/0.438 up the ladder to 2.760/2.700), across corners e (0.51 to 3.19 max), the washer-faced bearing dw max/min (0.428/0.418 upward — the washer face is the identifying "precision" feature of this standard), head height k (0.176/0.166 to 0.500/0.480), and fillet radius r max/min (0.025/0.015 rising to 0.045/0.02). One segment shows a "/" cell where a thread count is not tabulated — carried verbatim. Against the registered BS 3692 metric-era identity, this is the pre-metrication inch-thread ladder.
| Standard / scope | BS 1083-1965 precision hexagon head screws, washer faced — B.S.W. and B.S.F. threads, sizes as tabulated in two unlabelled segments (source order preserved) |
|---|---|
| Threads per inch | BSW ladder 20, 18, 16, 14, 12, 12, 11, 10 then 9...4.5 as printed, with one '/' no-value cell carried verbatim |
| Width across flats s | Max/min: 0.445/0.438 (smallest size) to 2.760/2.700 in (largest) |
| Washer face dw | Max/min: 0.428/0.418 to 1.175/1.165 and continuing as printed — the washer face is the precision-feature identity |
| Head height k / fillet r | k max/min 0.176/0.166 to 0.500/0.480 in; r max/min 0.025/0.015 to 0.045/0.02 |
| Not tabulated | Strength grades (Whitworth-era strength lived in material specs), lengths, finishes — per RFQ |
Materials
- Heritage BSW/BSF hardware is a maintenance supply, not a design supply: new designs stopped specifying Whitworth threads decades ago, but mills, presses and machine tools built to BS 1083 still need exact-series replacements. Supply is typically medium-carbon steel, self-colour or zinced, cut or rolled to the Whitworth thread form (55-degree); state BSW vs BSF explicitly and expect thread-gauge verification — a modern ISO-metric fastener is close enough to bruise into a Whitworth hole and wreck both
Ordering & documentation
Documents
Shipments are backed by Mill Test Certificate (MTC), Dimensional Report, Salt Spray Test Report on request, with full batch traceability from raw material to finished product. Quality management follows the owner-confirmed compliance list: ISO 9001:2015, RoHS, REACH. Exact document sets are confirmed on the order.
Quotation
- The fastener family (BS 1083 Precision Hexagon Screws, Washer Faced (BSW and BSF Threads)) plus the standard designation from your drawing — DIN / ISO / JIS / ASTM / ANSI, or a drawing for custom parts.
- Size (diameter and length), thread type (metric or inch), property class or grade, and coating or finish.
- Quantity per size and your target delivery date.
- Destination country, and any required documents (for example a mill test certificate) so the quote includes them.
Sample & supply
Minimum order quantity is 10,000 pieces. Stock items run 3–7 days. Quantities or variants outside the standard range are confirmed at quotation.
Storage & shipping
Parts are packed for export and shipped factory-direct to buyers in Europe, Asia, the Americas and the Middle East. Store fasteners dry and protected until installation, and keep coated parts in their packaging until use; specific packing and preservation requirements can be stated on the order and confirmed at quotation.
Frequently asked questions
Is a BSW screw the same as a modern metric hex screw of similar diameter?
No — and mixing them is the classic heritage-maintenance failure. The Whitworth thread form is 55-degree with rounded roots and crests and a different pitch ladder (a "3/8 BSW" runs 16 TPI where an M10 coarse runs 1.5 mm pitch), and BS 1083 adds the washer face under the head. The two will appear to start threading and then jam or strip. The table's threads-per-inch rows and washer-face dw rows are exactly the two checks that catch the mix-up before assembly: gauge the thread, look for the face. Order by the BSW/BSF designation and TPI as the machine's parts list prints it.
Why are there two unlabeled geometry segments in the table?
The collected page prints the BSW and BSF ladders as two same-width grids without series labels on the collected snapshot, so the batch carries them in source order and flags the split as positional — reading which segment is which series requires the thread-count rows (the finer TPI ladder is the BSF fine series). For ordering purposes this changes nothing: the designation you quote (BSW or BSF, size, TPI) selects the row, and the geometry is the standard's either way. If a restoration requires absolute certainty of segment, verify the physical part against a Whitworth thread gauge after receipt.
Related knowledge
- Thread-Forming vs Thread-Cutting vs Thread-Rolling Self-Tapping Screws: What the Evidence Settles on Base Material
- Screw Family Selection by Base Material: Wood, Machine and Self-Tapping Threads, Engagement and Coating
- Hex Bolts vs Socket Head Cap Screws: What the Evidence Settles on Strength, Clearance and Cost
Request a Quote
Get factory-direct pricing from the manufacturer.
What to include in your inquiry
- ✓ Standard and property class (e.g. DIN 912, ISO 4762, class 8.8) — or a drawing for custom parts.
- ✓ Sizes, lengths and thread type (metric or inch).
- ✓ Quantity per size and your target delivery date.
- ✓ Destination country, plus any coating or finish requirement.
- ✓ Any documents you need with the shipment (e.g. mill test certificate) so the quote includes them.
- ✓ Your inquiry goes straight to the factory team by email and gets a reply within 24 hours.
- ✓ Factory-direct pricing
- ✓ Standard and custom specifications
- ✓ Factory-direct export to buyers in Europe, Asia, the Americas and the Middle East
- ✓ Full fastener family support