Legacy Metric Hexagon Bolts, Nuts & Washers – BS 3692 & BS 4320

This page preserves the original RoyMech dimensional data for older metric hexagon bolts, nuts and washers. It is intended for old drawings, existing machinery, identification, maintenance and replacement work.

Need help selecting a bolt, screw or threaded fastener? See the Fastener Selection Guide for guidance on fastener types, threads, strength classes, loading, preload, tightening, thread engagement, locking, studs and anchors.

Legacy reference: these tables are historical RoyMech data based principally on BS 3692:1967, BS 3643 and BS 4320:1968. For new design use Current ISO Metric Hexagon Bolts, Nuts and Washers.

Coarse bolts · Coarse nuts · Fine bolts · Fine nuts · Bright washers · Black washers

ISO Metric Precision Hexagon Bolts – Coarse Thread Series

Legacy bolt tolerance class 6g. Thread form and limits were referenced to BS 3643; the original RoyMech hexagon product data was based on BS 3692.

Legacy ISO metric external screw thread dimensions

Legacy metric hexagon bolt dimensions

Nominal size	Pitch	Major d max–min	Minor d3 max–min	Pitch diameter d2 max–min	Bolt head thickness Zb	A/F max–min	A/C
M3	0,5	2,980 - 2,874	2,439 -2,272	2,655 - 2,580	2,125	5,50 - 5,38	6,40
M4	0,7	3,978 - 3,838	3,220 - 3,002	3,523 - 3,433	2,925	7,00 - 6,85	8,10
M5	0,8	4,976 - 4,826	4,110 - 3,869	4,456 - 4,361	3,650	8,00 - 7,85	9,20
M6	1,0	5,974 - 5,794	4,891 - 4,596	5,324 - 5,212	4,150	10,00 - 9,78	11,50
M8	1,25	7,972 - 7,760	6,619 - 6,272	7,160 - 7,042	5,650	13,00 - 12,73	15,00
M10	1,5	9,968 - 9,732	8,344 - 7,938	8,994 - 8,862	7,180	17,00 - 16,73	19,60
M12	1,75	11,966 - 11,701	10,072 - 9,601	10,829 - 10,679	8,180	19,00 - 18,67	22,10
M16	2,0	15,962 - 15,682	13,797 - 13,271	14,663 - 14,503	10,180	24,00 - 23,67	27,70
M20	2,5	19,958 - 19,623	17,252 - 16,624	18,334 - 18,164	13,215	30,00 - 29,67	34,60
M24	3,0	23,952 - 23,577	20,701 - 19,955	22,003 - 21,803	15,215	36,00 - 35,58	41,60
M30	3,50	29,947 - 29,522	26,158 - 25,306	27,674 - 27,462	19,260	46,00 - 45,38	53,1
M36	4,00	35,940 - 35,465	31,610 - 30,654	33,342 - 33,118	23,260	55,00 - 54,26	63,5

Data correction: the M5 and M8 minor-diameter ranges were reversed in the old HTML source. The existing numerical endpoints have only been restored to max–min order.

ISO Metric Precision Hexagon Nuts – Coarse Thread Series

Legacy nut tolerance class 6H. The original RoyMech data referenced BS 3692 for the nut and BS 3643 for the metric thread.

Legacy ISO metric internal screw thread dimensions

Legacy metric hexagon nut dimensions

Nominal size	Pitch	Major diameter D	Minor D1 max–min	Nut thickness Zn
M3	0,5	3,000	2,599 - 2,459	2,40
M4	0,7	4,000	3,422 - 3,242	3,20
M5	0,8	5,000	4,334 - 4,134	4,00
M6	1,0	6,000	5,153 - 4,917	5,00
M8	1,25	8,000	6,912 - 6,647	6,50
M10	1,5	10,000	8,676 - 8,376	8,00
M12	1,75	12,000	10,441 - 10,106	10,00
M16	2,0	16,000	14,210 - 13,835	13,00
M20	2,5	20,000	17,744 - 17,294	16,00
M24	3,0	24,000	21,252 - 20,752	19,00
M30	3,5	30,000	26,771 - 26,211	24,00
M36	4,0	36,00	32,270 - 31,670	29,00

ISO Metric Precision Hexagon Bolts – Fine Thread Series

Legacy BS 3692-based fine-thread bolt data with external metric thread tolerance class 6g.

Nominal size	Pitch	Major d max–min	Minor diameter max–min	Pitch diameter max–min	Bolt head thickness Zb	A/F max–min	A/C
M6	0,75	5,978 - 5,838	5,166 - 4,929	5,491 - 5,391	4,150	10,00 - 9,78	11,50
M8	1,00	7,974 - 7,794	6,891 - 6,596	7,324 - 7,212	5,650	13,00 - 12,73	15,00
M10	1,25	9,972 - 9,760	8,619 - 8,272	9,160 - 9,042	7,180	17,00 - 16,73	19,60
M12	1,25	11,972 - 11,760	10,619 - 10,258	11,160 - 11,028	8,180	19,00 - 18,67	22,10
M16	1,50	15,968 - 15,732	14,344 - 13,930	14,994 - 14,854	10,180	24,00 - 23,67	27,70
M20	1,5	19,968 - 19,732	18,344 - 17,930	18,994 - 18,854	13,215	30,00 - 29,67	34,60
M24	2,0	23,962 - 23,682	21,797 - 21,261	22,663 - 22,493	15,215	36,00 - 35,58	41,60
M30	2,0	29,962 - 29,682	27,797 - 27,261	28,663 - 28,493	19,260	46,00 - 45,38	53,1
M36	3,00	35,952 - 35,577	32,704 - 31,955	34,003 - 33,803	23,260	55,00 - 54,26	63,5

ISO Metric Precision Hexagon Nuts – Fine Thread Series

Legacy BS 3692-based fine-thread nut data with internal metric thread tolerance class 6H.

Nominal size	Pitch	Major diameter	Minor diameter max–min	Nut thickness Zn
M6	0,75	6,000	5,378 - 5,188	5,00
M8	1,00	8,000	7,153 - 6,917	6,50
M10	1,25	10,000	8,912 - 8,647	8,00
M12	1,25	12,000	10,912 - 10,647	10,00
M16	1,50	16,000	14,676 - 14,376	13,00
M20	1,50	20,000	18,676 - 18,376	16,00
M24	2,0	24,000	22,210 - 21,835	19,00
M30	2,0	30,000	28,210 - 27,835	24,00
M36	3,0	36,00	33,252 - 32,752	29,00

Bright Metric Plain Washers – BS 4320:1968

The original RoyMech bright metric washer data is retained for legacy engineering work.

Nominal size	Internal dia. max–min	External dia. max–min	Thickness max–min	Thin
M3	3,4 - 3,2	7,0 - 6,7	0,6 - 0,4	-
M4	4,5 - 4,3	9,0 - 8,7	0,9 - 0,7	-
M5	5,5 - 5,3	10,0 - 9,7	1,1 - 0,9	-
M6	6,7 - 6,4	12,5 - 12,1	1,8 - 1,4	0,9 - 0,7
M8	8,7 - 8,4	17,0 - 16,6	1,8 - 1,4	1,1 - 0,9
M10	10,9 - 10,5	21,0 - 20,5	2,2 - 1,8	1,45 - 1,05
M12	13,4 - 13,0	24,0 - 23,5	2,7 - 2,3	1,8 - 1,4
M16	17,4 - 17,00	30,0 - 29,5	3,3 - 2,7	2,2 - 1,8
M20	21,5 - 21,0	37,0 - 36,2	3,3 - 2,7	2,2 - 1,8
M24	25,5 - 25,0	44,0 - 43,2	4,3 - 3,7	2,7 - 2,3
M30	31,6 - 31,0	56,0 - 55,0	4,3 - 3,7	2,7 - 2,3
M36	37,6 - 37,0	66,0 - 65,0	5,6 - 4,4	3,3 - 2,7

Black Metric Plain Washers – BS 4320:1968

The original RoyMech black metric washer data is retained for legacy engineering work.

Nominal size	Internal dia. max–min	External dia. max–min	Thickness max–min
M5	5,8 - 5,5	10,0 - 9,2	1,2 - 0,8
M6	7,0 - 6,6	12,5 - 11,7	1,9 - 1,3
M8	9,4 - 9,0	17,0 - 16,2	1,9 - 1,3
M10	11,5 - 11,0	21,0 - 20,2	2,3 - 1,7
M12	14,5 - 14,0	24,0 - 23,2	2,8 - 2,2
M16	18,5 - 18,00	30,0 - 29,2	3,6 - 2,4
M20	22,6 - 22,0	37,0 - 35,8	3,6 - 2,4
M24	26,6 - 26,0	44,0 - 42,8	4,6 - 3,4
M30	33,8 - 33,0	56,0 - 54,5	4,6 - 3,4
M36	39,8 - 39,0	66,0 - 64,5	6,0 - 4,0
M42	45,8 - 45,0	78,0 - 76,5	8,2 - 5,8
M48	53,0 - 52,0	92,0 -90,0	9,2 - 6,8

Related RoyMech References

External References

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Legacy Metric Hexagon Bolts, Nuts and Washers