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Legacy BS 3692 / BS 4320 Hexagon Bolts, Nuts and Washers

Legacy BS 3692 hexagon bolt and nut limits of size (coarse and fine threads, M3 - M36, decimal-comma notation as printed) with BS 4320 normal and large plain-washer series — the pre-ISO British tabulation still referenced on legacy drawings, carried verbatim with its max-min limit pairs.

Last updated: 2026-11

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Legacy BS 3692 / BS 4320 Hexagon Bolts, Nuts and Washers in an industrial setting
Illustrative image redrawn from real product references — not a photograph of stocked items.

Specifications

Legacy British drawings still call out BS 3692 hexagon bolts and BS 4320 washers, and their limits differ in the details from the current ISO hexagon line — enough to matter when a legacy fastener must mate with modern tooling. The collected page tabulates, in its own decimal-comma notation: the bolt coarse limits (major d max-min as one cell, e.g. M12 "11,966 - 11,701"; minor d3; pitch diameter d2; head thickness Zb; A/F max-min; A/C across corners), the same ladder for fine threads (M6x0,75 through M36x3,00), the nut tables (major D nominal, minor D1 max-min, nut thickness Zn), and the two BS 4320 washer series (normal M3 - M36 and large M5 - M48, internal/external diameter and thickness max-min pairs, with a Thin column on the normal series). Two carried-verbatim quirks to note when reading: the M36 rows print "36,00" (two decimals against the three-decimal column pattern) and the A/C column drops to one decimal at M30/M36 ("53,1", "63,5") — all flagged under the tables, not normalized. Compare against the current ISO hexagon reference in the bolts family when a drawing permits either standard; where they diverge (the BS washer OD ladder runs slightly larger than ISO at some sizes), the drawing's callout governs. Strength grades and finish are not tabulated — per RFQ.

Bolt coarse limits M3 - M36: major d, minor d3, pitch dia d2 max-min pairs, Zb head thickness, A/F max-min, A/C across corners
Bolt fine limits M6x0,75 - M36x3,00: same column set, per the fine ladder
Nut tables Coarse M3 - M36 and fine M6 - M36: major D nominal, minor D1 max-min, thickness Zn
Washers BS 4320 Normal series M3 - M36 (plus Thin column M6 up), large series M5 - M48; internal/external dia and thickness max-min pairs
Notation Decimal commas throughout, max-min pairs in single cells with an en dash — carried verbatim
Not tabulated Strength grades, proof loads, finish, thread tolerance classes — per RFQ
BS 3692 hexagon bolts — coarse thread limits (d, d3, d2, Zb, A/F, A/C)As printed on the collected page: legacy BS 3692 / BS 4320 limits in mm, decimal-comma notation carried verbatim. max-min pairs print as one cell with an en dash. Verification: token-for-token equal to the x127 corpus (live-DOM capture 2026-11-01).
Nominal sizePitchMajor d max–minMinor d3 max–minPitch diameter d2 max–minBolt head thickness ZbA/F max–minA/C
M30,52,980 - 2,8742,439 -2,2722,655 - 2,5802,1255,50 - 5,386,40
M40,73,978 - 3,8383,220 - 3,0023,523 - 3,4332,9257,00 - 6,858,10
M50,84,976 - 4,8264,110 - 3,8694,456 - 4,3613,6508,00 - 7,859,20
M61,05,974 - 5,7944,891 - 4,5965,324 - 5,2124,15010,00 - 9,7811,50
M81,257,972 - 7,7606,619 - 6,2727,160 - 7,0425,65013,00 - 12,7315,00
M101,59,968 - 9,7328,344 - 7,9388,994 - 8,8627,18017,00 - 16,7319,60
M121,7511,966 - 11,70110,072 - 9,60110,829 - 10,6798,18019,00 - 18,6722,10
M162,015,962 - 15,68213,797 - 13,27114,663 - 14,50310,18024,00 - 23,6727,70
M202,519,958 - 19,62317,252 - 16,62418,334 - 18,16413,21530,00 - 29,6734,60
M243,023,952 - 23,57720,701 - 19,95522,003 - 21,80315,21536,00 - 35,5841,60
M303,5029,947 - 29,52226,158 - 25,30627,674 - 27,46219,26046,00 - 45,3853,1
M364,0035,940 - 35,46531,610 - 30,65433,342 - 33,11823,26055,00 - 54,2663,5
  • Row 12 (M36): A/C prints "53,1" at M30 and "63,5" at M36 (one decimal place vs three elsewhere in the column) — as printed, not normalized
BS 3692 hexagon nuts — coarse thread (D, D1, Zn)As printed on the collected page: legacy BS 3692 / BS 4320 limits in mm, decimal-comma notation carried verbatim. max-min pairs print as one cell with an en dash. Verification: token-for-token equal to the x127 corpus (live-DOM capture 2026-11-01).
Nominal sizePitchMajor diameter DMinor D1 max–minNut thickness Zn
M30,53,0002,599 - 2,4592,40
M40,74,0003,422 - 3,2423,20
M50,85,0004,334 - 4,1344,00
M61,06,0005,153 - 4,9175,00
M81,258,0006,912 - 6,6476,50
M101,510,0008,676 - 8,3768,00
M121,7512,00010,441 - 10,10610,00
M162,016,00014,210 - 13,83513,00
M202,520,00017,744 - 17,29416,00
M243,024,00021,252 - 20,75219,00
M303,530,00026,771 - 26,21124,00
M364,036,0032,270 - 31,67029,00
  • Row 12 (M36): major diameter prints "36,00" (two decimals vs "3,000" pattern) at M36 — as printed
BS 3692 hexagon bolts — fine thread limits (d, d3, d2, Zb, A/F, A/C)As printed on the collected page: legacy BS 3692 / BS 4320 limits in mm, decimal-comma notation carried verbatim. max-min pairs print as one cell with an en dash. Verification: token-for-token equal to the x127 corpus (live-DOM capture 2026-11-01).
Nominal sizePitchMajor d max–minMinor diameter max–minPitch diameter max–minBolt head thickness ZbA/F max–minA/C
M60,755,978 - 5,8385,166 - 4,9295,491 - 5,3914,15010,00 - 9,7811,50
M81,007,974 - 7,7946,891 - 6,5967,324 - 7,2125,65013,00 - 12,7315,00
M101,259,972 - 9,7608,619 - 8,2729,160 - 9,0427,18017,00 - 16,7319,60
M121,2511,972 - 11,76010,619 - 10,25811,160 - 11,0288,18019,00 - 18,6722,10
M161,5015,968 - 15,73214,344 - 13,93014,994 - 14,85410,18024,00 - 23,6727,70
M201,519,968 - 19,73218,344 - 17,93018,994 - 18,85413,21530,00 - 29,6734,60
M242,023,962 - 23,68221,797 - 21,26122,663 - 22,49315,21536,00 - 35,5841,60
M302,029,962 - 29,68227,797 - 27,26128,663 - 28,49319,26046,00 - 45,3853,1
M363,0035,952 - 35,57732,704 - 31,95534,003 - 33,80323,26055,00 - 54,2663,5
  • Row 8 (M30): A/C prints "53,1" at M30 — as printed in table 1
BS 3692 hexagon nuts — fine thread (D, D1, Zn)As printed on the collected page: legacy BS 3692 / BS 4320 limits in mm, decimal-comma notation carried verbatim. max-min pairs print as one cell with an en dash. Verification: token-for-token equal to the x127 corpus (live-DOM capture 2026-11-01).
Nominal sizePitchMajor diameterMinor diameter max–minNut thickness Zn
M60,756,0005,378 - 5,1885,00
M81,008,0007,153 - 6,9176,50
M101,2510,0008,912 - 8,6478,00
M121,2512,00010,912 - 10,64710,00
M161,5016,00014,676 - 14,37613,00
M201,5020,00018,676 - 18,37616,00
M242,024,00022,210 - 21,83519,00
M302,030,00028,210 - 27,83524,00
M363,036,0033,252 - 32,75229,00
BS 4320 plain washers — normal series (internal/external dia, thickness)As printed on the collected page: legacy BS 3692 / BS 4320 limits in mm, decimal-comma notation carried verbatim. max-min pairs print as one cell with an en dash. Verification: token-for-token equal to the x127 corpus (live-DOM capture 2026-11-01).
Nominal sizeInternal dia. max–minExternal dia. max–minThickness max–minThin
M33,4 - 3,27,0 - 6,70,6 - 0,4-
M44,5 - 4,39,0 - 8,70,9 - 0,7-
M55,5 - 5,310,0 - 9,71,1 - 0,9-
M66,7 - 6,412,5 - 12,11,8 - 1,40,9 - 0,7
M88,7 - 8,417,0 - 16,61,8 - 1,41,1 - 0,9
M1010,9 - 10,521,0 - 20,52,2 - 1,81,45 - 1,05
M1213,4 - 13,024,0 - 23,52,7 - 2,31,8 - 1,4
M1617,4 - 17,0030,0 - 29,53,3 - 2,72,2 - 1,8
M2021,5 - 21,037,0 - 36,23,3 - 2,72,2 - 1,8
M2425,5 - 25,044,0 - 43,24,3 - 3,72,7 - 2,3
M3031,6 - 31,056,0 - 55,04,3 - 3,72,7 - 2,3
M3637,6 - 37,066,0 - 65,05,6 - 4,43,3 - 2,7
BS 4320 plain washers — large series (internal/external dia, thickness)As printed on the collected page: legacy BS 3692 / BS 4320 limits in mm, decimal-comma notation carried verbatim. max-min pairs print as one cell with an en dash. Verification: token-for-token equal to the x127 corpus (live-DOM capture 2026-11-01).
Nominal sizeInternal dia. max–minExternal dia. max–minThickness max–min
M55,8 - 5,510,0 - 9,21,2 - 0,8
M67,0 - 6,612,5 - 11,71,9 - 1,3
M89,4 - 9,017,0 - 16,21,9 - 1,3
M1011,5 - 11,021,0 - 20,22,3 - 1,7
M1214,5 - 14,024,0 - 23,22,8 - 2,2
M1618,5 - 18,0030,0 - 29,23,6 - 2,4
M2022,6 - 22,037,0 - 35,83,6 - 2,4
M2426,6 - 26,044,0 - 42,84,6 - 3,4
M3033,8 - 33,056,0 - 54,54,6 - 3,4
M3639,8 - 39,066,0 - 64,56,0 - 4,0
M4245,8 - 45,078,0 - 76,58,2 - 5,8
M4853,0 - 52,092,0 -90,09,2 - 6,8

Materials

  • BS 3692 hardware on legacy drawings is typically carbon steel to the old BS strength markings or stainless where the environment demands; the current supply line manufactures to the ISO-equivalent geometry under the BS designation on request. When you RFQ a legacy callout, give the drawing reference and the environment — we quote the current-manufacture equivalent and flag any geometry divergence from the limits on this table

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 (Legacy BS 3692 / BS 4320 Hexagon Bolts, Nuts and Washers) 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 BS 3692 bolt interchangeable with its current ISO equivalent?

Largely yes on the wrench-facing geometry — the A/F ladder (5,50 at M3 through 55,00 at M36) matches the ISO wrench series, and the major/pitch diameter limits sit in the same tolerance system. The differences live at the edges: head heights and corner (A/C) values have small divergences from the current ISO hexagon tabulation, and BS 4320 washer ODs run differently from ISO 7089 at some sizes — enough that a mixed legacy/modern assembly should be checked against both ladders, not assumed. Practically: if the drawing names BS 3692, quote against the BS limits on this table and note the current-manufacture basis on the RFQ response; if the drawing permits "or equivalent", the ISO tabulation in the bolts family is the tighter current reference. Where the two standards disagree on a limit that matters to your joint (a counterbore, a clearance hole), the drawing callout governs — not either table.

Related knowledge

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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

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