Hex Flange Nuts Manufacturer in India | ISO 4161, DIN 6923 Flange Nuts

Overview

ISO 4161, DIN 6923 Flange Nuts: Manufacturer & Stockist

A hex flange nut carries its washer with it. The flange spreads the clamp force over a wider ring than the hexagon alone, so the nut presses less on soft, thin or painted parts, and there is no loose washer to drop or forget.

Exotic Alloy manufactures, stocks and exports hex flange nuts from Mumbai, India, for vehicle and equipment builders, sheet-metal and enclosure makers, HVAC and electrical contractors, and fastener distributors. We supply across India and to Qatar, the Gulf, Africa and South-East Asia.

Metric and inch

Metric flange nuts follow ISO 4161, EN 1661 or the older German DIN 6923, which agree in every size except the M10 spanner. Inch flange nuts follow ASME B18.2.2. The prevailing-torque version with a nylon ring is ISO 7043 / DIN 6926; see also nylock nuts, hex nuts and the 12-point flange nuts for high-strength joints.

ISO 4161 EN 1661 DIN 6923 ASME B18.2.2 Nylon insert

Hex flange nuts at a glance

Metric: ISO 4161:2012, EN 1661, DIN 6923, M5–M20
Inch: ASME B18.2.2, #6–3/4 in UNC
Spanner: 15 mm at M10 (EN 1661: 16 mm)
Height: Up to 1.0 d, flange included
Bearing area: 2.8–4.1× an ISO 4032 nut
Classes: 8, 10, 12, A2-70 (EN 1661)
Related: Nylock nuts, hex nuts, washers

An ISO 4161 M10 flange nut to scale. The flange is 21.8 mm across at most; the flat ring that bears on the part is at least 19.6 mm across, against 14.63 mm for a plain ISO 4032 nut.

Specification

Hex Flange Nut Specification

The range we manufacture, stock and export.

StandardsISO 4161, EN 1661, DIN 6923, ASME B18.2.2

Nylon insertISO 7043, DIN 6926

SizesM5–M20; #6–3/4 in

ThreadMetric coarse; UNC

Product gradeA up to M16, B at M20 (ISO 4161)

Steel classes8, 10, 12

StainlessA2-70 (304); A4 (316) on request

FinishPlain, zinc plated, zinc flake; stainless passivated

CertificationEN 10204 3.1; 3.2 on request

SupplyFrom stock or made to order, boxed by size

ISO 4161

ISO 4161 Hex Flange Nut Dimensions

Hexagon nuts with flange, coarse thread, mm.

Size	Pitch P	Spanner s max / min	e min	Height m max / min	Flange d_c max	Bearing d_w min	Flange c min	m_w min
M5	0.8	8 / 7.78	8.79	5 / 4.7	11.8	9.8	1	2.5
M6	1	10 / 9.78	11.05	6 / 5.7	14.2	12.2	1.1	3.1
M8	1.25	13 / 12.73	14.38	8 / 7.64	17.9	15.8	1.2	4.6
M10	1.5	15 / 14.73	16.64	10 / 9.64	21.8	19.6	1.5	5.6
M12	1.75	18 / 17.73	20.03	12 / 11.57	26	23.8	1.8	6.8
M14	2	21 / 20.67	23.36	14 / 13.3	29.9	27.6	2.1	7.7
M16	2	24 / 23.67	26.75	16 / 15.3	34.5	31.9	2.4	8.9
M20	2.5	30 / 29.16	32.95	20 / 18.7	42.8	39.9	3	10.7

ISO 4161:2012 (same values as 1999). s across flats, e across corners, m overall height including the flange, d_c flange diameter, d_w diameter of the flat bearing ring, c flange thickness at the edge, m_w wrenching height. The overall height m max equals the thread diameter at every size.

EN 1661 & DIN 6923

ISO 4161, EN 1661 and DIN 6923 Compared

Spanner size in mm; everything else is the same.

Size	ISO 4161	EN 1661	DIN 6923 (old)	ISO 4032 nut	Flange vs ISO 4032 nut bearing area
M5	8	8	8	8	52 vs 17 mm² (3.0×)
M6	10	10	10	10	83 vs 28 mm² (3.0×)
M8	13	13	13	13	132 vs 43 mm² (3.1×)
M10	15	16	15	16	207 vs 73 mm² (2.8×)
M12	18	18	18	18	302 vs 74 mm² (4.1×)
M14	21	21	21	21	410 vs 114 mm² (3.6×)
M16	24	24	24	24	559 vs 157 mm² (3.6×)
M20	30	30	30	30	870 vs 222 mm² (3.9×)

Pitch, height, flange diameter, flange thickness and bearing diameter agree in all three standards. M10 is the one difference: EN 1661 uses a 16 mm spanner (e min 17.77, m_w min 5.9), ISO 4161 and DIN 6923 use 15 mm (e min 16.64, m_w min 5.6). EN 1661 covers M5 to M20 in property classes 8, 10 and 12 and stainless A2-70. Bearing areas are our calculation on an ISO 273 medium clearance hole.

Bearing area

Why the Flange: Bearing Area and Surface Pressure

The flange is a washer that cannot go missing. At M10 it bears on 2.8 times the area of a plain nut and about as much as a nut on an ISO 7089 washer.

2.8 to 4.1 times the bearing area, M5 to M20. Hover a bar for the value.

Surface pressure = clamp force ÷ bearing area. The same force on 2.8 times the area gives 2.8 times lower pressure.
Lower pressure means less embedding into soft metals, plastics and paint, so less of the preload is lost after tightening.

Against a nut and washer: within 6 % of the area of an ISO 4032 nut on an ISO 7089 washer from M5 to M14, larger at M16 and M20.
One part instead of two: faster assembly and no missing washers.

Inch & nylon insert

ASME Hex Flange Nuts and Nylon-Insert Flange Nuts

ASME B18.2.2 hex flange nuts, UNC, inches.

Size	UNC tpi	Across flats max / min, in	Flange ⌀ max / min, in	Thickness max / min, in	Flange min, in	Wrenching min, in
#6	32	0.312 / 0.302	0.422 / 0.406	0.171 / 0.156	0.02	0.10
#8	32	0.344 / 0.334	0.469 / 0.452	0.203 / 0.187	0.02	0.13
#10	24	0.375 / 0.365	0.500 / 0.480	0.219 / 0.203	0.03	0.13
#12	24	0.438 / 0.428	0.594 / 0.574	0.236 / 0.222	0.04	0.14
1/4	20	0.438 / 0.428	0.594 / 0.574	0.236 / 0.222	0.04	0.14
5/16	18	0.500 / 0.489	0.680 / 0.660	0.283 / 0.268	0.04	0.17
3/8	16	0.562 / 0.551	0.750 / 0.728	0.347 / 0.330	0.04	0.23
7/16	14	0.688 / 0.675	0.937 / 0.910	0.395 / 0.375	0.04	0.26
1/2	13	0.750 / 0.736	1.031 / 1.000	0.458 / 0.437	0.05	0.31
9/16	12	0.875 / 0.861	1.188 / 1.155	0.506 / 0.483	0.05	0.35
5/8	11	0.938 / 0.922	1.281 / 1.248	0.569 / 0.545	0.05	0.40
3/4	10	1.125 / 1.088	1.500 / 1.460	0.675 / 0.627	0.06	0.46

ASME B18.2.2-2022 (same values as 2015). Thickness is overall, flange included; flange min is the thickness at the flange edge; wrenching min is the height of the hexagon flats. #12 and 1/4 in share one body. ASME also lists large hex flange nuts with wider flanges, made to order.

The nylon-insert flange nut, as in the photo. Same hexagon and flange; a polyamide ring on top grips the bolt thread.

Size	Spanner s	Overall height h max nylon insert	Plain flange nut m max ISO 4161	Extra height
M5	8	7.1	5	+2.1
M6	10	9.1	6	+3.1
M8	13	11.1	8	+3.1
M10	15	13.5	10	+3.5
M12	18	16.1	12	+4.1
M14	21	18.2	14	+4.2
M16	24	20.3	16	+4.3
M20	30	24.8	20	+4.8

ISO 7043:2012 prevailing-torque hexagon nuts with flange and non-metallic insert, mm; DIN 6926 gives the same h max. Spanner, flange and flange thickness are those of ISO 4161. Allow the extra height when choosing the bolt length: the thread must pass fully through the insert.

Finder

Flange Nut Finder: Dimensions & Surface Pressure

Pick the nut and the clamp force; get its dimensions, the pressure under it and the order line.

Nut & joint

Standard

Size

Clamp force, kN

Quantity

Material

Dimensions from the tables on this page. Bearing area = π/4 (d_w² − hole²) on an ISO 273 medium clearance hole, compared with an ISO 4032 nut; pressure = clamp force ÷ area. Compare the pressure with what the clamped material allows. Metric only: ASME and ISO 7043 give no d_w in our sources.

Result

97

MPa under the flange nut

274

MPa under an ISO 4032 nut

Spanner / height:15 / 10 mm

Flange:⌀ 21.8 max, 1.5 thick min

Bearing area:207 vs 73 mm² (2.8×)

Designation:1000 pcs hexagon flange nut ISO 4161 – M10, steel, zinc plated

Materials

Flange Nut Materials & Finishes

Material	Class	Finish	Where
Carbon steel	8	Zinc plated, zinc flake, plain	Vehicles, equipment, enclosures, with class 8.8 bolts
Alloy or carbon steel, hardened	10, 12	Zinc flake, phosphated	With class 10.9 and 12.9 bolts
Stainless A2 (304)	A2-70	Passivated	Indoor, food and electrical equipment
Stainless A4 (316)	On request	Passivated	Outdoor, coastal and chemical areas

EN 1661 lists classes 8, 10, 12 and A2-70. Match the nut class to the bolt class: class 8 on 8.8, class 10 on 10.9, class 12 on 12.9.

Carbon steel

Class 8 · 10

Zinc plated or zinc flake.

1010 1035

Stainless

A2-70 · A4

As in the photo.

304 316

Nylon insert

Polyamide ring

ISO 7043 / DIN 6926.

Nylock nuts

Manufacturing

How Our Hex Flange Nuts Are Made

1

Wire

Steel or stainless wire, certified by heat.

2

Form

Hexagon and flange cold formed in one piece, hole pierced.

3

Tap

Thread tapped; nylon ring fitted and rolled in for ISO 7043.

4

Heat treat

Classes 10 and 12 hardened and tempered.

5

Finish

Zinc plated, zinc flake or passivated.

6

Inspect

Thread, flange and proof load checked.

Applications

Where Our Hex Flange Nuts Are Used

Vehicles

Body, chassis and trim fixings.

Enclosures & panels

Thin sheet that needs a wide bearing face.

HVAC & ducting

Fans, flanges and duct supports.

Machinery

Guards, frames and covers.

Electrical

Cable trays, earthing and busbar supports.

Solar structures

Module rails and mounting frames.

Quality & testing

Hex Flange Nut Inspection & Certification

Check	Method	Applied to
Thread	GO / NOT GO plug gauges	Every lot
s, m, flange d_c, c	Calipers, micrometer	Every lot
Proof load	Tensile machine, ISO 898-2 / ISO 3506-2	Every lot
Hardness	Rockwell or Vickers	Heat-treated lots
Prevailing torque	Torque test, ISO 2320	Nylon-insert lots
Coating	Thickness gauge, salt spray on request	Coated lots

Every shipment includes

EN 10204 3.1 certificate
Lot number on every box
Packing list by size

On request

EN 10204 3.2 with third-party inspection
Salt spray tests on coated nuts
Sets with bolts

FAQ

Hex Flange Nut Questions, Answered

A hexagon nut with a wide flange formed on its bearing end. The flange works like a built-in washer: it spreads the clamp force over a larger area and cannot be lost or left out. Metric flange nuts are made to ISO 4161, EN 1661 and DIN 6923 from M5 to M20; inch flange nuts to ASME B18.2.2 from #6 to 3/4 in.

One size. All three give the same pitch, height, flange diameter, flange thickness and bearing diameter from M5 to M20, but at M10 EN 1661 uses a 16 mm spanner, while ISO 4161 and DIN 6923 use 15 mm. Check the spanner size when an M10 drawing quotes EN 1661.

On an ISO 273 medium clearance hole, 2.8 to 4.1 times the area of an ISO 4032 nut. At M10 the flange nut bears on at least 19.6 mm against 14.63 mm, which is 207 against 73 square millimetres on an 11 mm hole, so the pressure under it is 2.8 times lower for the same clamp force.

In bearing area, yes. From M5 to M14 the flange nut bears on an area within 6 % of an ISO 4032 nut on an ISO 7089 washer, and at M16 and M20 on a larger one. It also saves a part and an assembly step.

To ISO 4161: 8, 10, 13, 15, 18, 21, 24 and 30 mm for M5, M6, M8, M10, M12, M14, M16 and M20. At M10 that is 15 mm, one size smaller than the 16 mm of an ISO 4032 nut; EN 1661 keeps 16 mm at M10.

Its height including the flange is at most equal to the thread diameter: 10 mm at M10, against 8.4 mm for an ISO 4032 nut. An ISO 7043 flange nut with a nylon insert is taller, up to 13.5 mm at M10.

EN 1661 lists steel property classes 8, 10 and 12 and stainless steel A2-70. The nuts in the photo are A2-70 flange nuts with a nylon insert. We also make A4 stainless flange nuts on request.

ASME B18.2.2 covers hex flange nuts from #6 to 3/4 in with UNC threads. A 1/2-13 nut is 3/4 in across flats, with a flange 1.000 to 1.031 in across and 0.437 to 0.458 in thick overall.

Metric and inch

Nut & joint

Result

Carbon steel

Stainless

Nylon insert

Wire

Form

Tap

Heat treat

Finish

Inspect

Vehicles

Enclosures & panels

HVAC & ducting

Machinery

Electrical

Solar structures

Every shipment includes

On request

What is a hex flange nut?

What is the difference between ISO 4161, EN 1661 and DIN 6923?

How much larger is the bearing face of a flange nut?

Does a flange nut replace a washer?

What spanner fits a flange nut?

How tall is a hex flange nut?

Which property classes do flange nuts come in?

What sizes are inch hex flange nuts?

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