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Nylon Insert Flange Lock Nut Dimensions (ISO 7043, M5 to M20)

Guide · Updated October 28, 2026

ISO 7043 covers prevailing torque hexagon nuts with flange and a non-metallic (nylon) insert, style 2, with metric coarse thread from M5 to M20, grade A through M16 and grade B for M20, property classes 8, 9 and 10. Hex, flange and bearing face match ISO 4161 plus the nylon locking collar. Values come from the ISO 7043 preview table, checked against the GlobalFastener ISO 7043 table and the Nufast ISO 7043 production drawing (every column, every size), with s, dc, h max and c also matching the VIPA ISO 7043 / DIN 6926 sheet. One minor conflict: VIPA lists M20 thread height m as 18.9 mm while ISO, GlobalFastener and Nufast list 18.7 mm min; we show 18.7. Not shown: da, c and r. For fine pitch, see ISO 12125.

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Step by step

Confirm coarse thread: ISO 7043 is coarse pitch: M6x1, M8x1.25, M10x1.5, M12x1.75, M16x2, M20x2.5. For fine pitch use ISO 12125.
Pick the wrench: Same hex as ISO 4161: M5 8 mm, M6 10 mm, M8 13 mm, M10 15 mm, M12 18 mm, M16 24 mm, M20 30 mm.
Check the flange: dc max is the clearance you need around the hole: M8 17.9 mm, M12 26.0 mm, M16 34.5 mm. No washer is needed.
Use total height for length: h max includes the nylon collar: M8 11.10 mm, M12 16.10 mm. Use h max for bolt length math.
Leave thread past the nut: Run at least 2 full threads past the top so the nylon ring is fully engaged.
Watch the temperature: Nylon inserts are normally limited to about 120 °C. For hot spots use an all-metal flange lock nut instead.

ISO 7043 nylon insert flange lock nut dimensions (mm)

Columns: thread size x pitch, width across flats s max and min (s max is the wrench size), total height h max and min, thread height m min, wrenching height mw min, width across corners e min, flange diameter dc max, bearing face diameter dw min. Sizes in parentheses should be avoided if possible.

Size | s max | s min | h max | h min | m min | mw min | e min | dc max | dw min
M5x0.8 | 8.00 | 7.78 | 7.10 | 6.52 | 4.70 | 2.5 | 8.79 | 11.8 | 9.8
M6x1 | 10.00 | 9.78 | 9.10 | 8.52 | 5.70 | 3.1 | 11.05 | 14.2 | 12.2
M8x1.25 | 13.00 | 12.73 | 11.10 | 10.40 | 7.64 | 4.6 | 14.38 | 17.9 | 15.8
M10x1.5 | 15.00 | 14.73 | 13.50 | 12.80 | 9.64 | 5.6 | 16.64 | 21.8 | 19.6
M12x1.75 | 18.00 | 17.73 | 16.10 | 15.40 | 11.57 | 6.8 | 20.03 | 26.0 | 23.8
(M14x2) | 21.00 | 20.67 | 18.20 | 16.90 | 13.30 | 7.7 | 23.36 | 29.9 | 27.6
M16x2 | 24.00 | 23.67 | 20.30 | 19.00 | 15.30 | 8.9 | 26.75 | 34.5 | 31.9
M20x2.5 | 30.00 | 29.16 | 24.80 | 22.70 | 18.70 | 10.7 | 32.95 | 42.8 | 39.9

Nylon vs plain vs fine pitch flange nut

For M12 all three take an 18 mm wrench and have a 26.0 mm flange. Height max: ISO 7043 nylon insert 16.10 mm, ISO 4161 plain 12.00 mm, ISO 12125 fine pitch nylon insert 16.10 mm. A visible nylon ring at the top means nylon insert.

Worked example: bolt length for an M8 nylon flange lock nut

Grip 12 mm, nut h max 11.10 mm, plus 2 threads at 1.25 mm = 2.5 mm. Total 25.6 mm, so an M8 x 30 works (M8 x 25 is too short).

Common problems

Fine bolt, coarse nut: it starts, then binds. Check pitch first.
Heat: nylon softens near exhaust and engine parts. Use an all-metal lock nut there.
Reuse: the nylon wears each time. Replace nuts on critical joints.

FAQ

What is the difference between ISO 7043 and ISO 4161?

ISO 4161 is the plain coarse thread hex flange nut. ISO 7043 has the same hex, flange and bearing face plus a nylon insert, so it is taller (M12 h max 16.10 mm vs 12.00 mm).

What is the difference between ISO 7043 and ISO 12125?

Both are nylon insert hex flange lock nuts with the same hex, flange and heights. ISO 7043 is coarse thread (M12x1.75); ISO 12125 is fine pitch (M12x1.5 or M12x1.25).

What is the difference between ISO 7043 and ISO 7040?

ISO 7040 is a nylon insert lock nut without a flange. ISO 7043 has a built-in flange that spreads load like a washer. Note the hex differs at M10 (ISO 7043 15 mm, ISO 7040 16 mm).

Is ISO 7043 the same as DIN 6926?

DIN 6926 is the older German nylon insert flange nut that ISO 7043 replaced. Check the wrench size before mixing them, since older DIN parts can use larger hexes at some sizes.

What wrench fits an M10 nylon flange lock nut?

15 mm for ISO 7043. ISO flange nuts use 15 mm at M10, not 16 or 17 mm.

How tall is an M8 nylon insert flange lock nut?

11.10 mm max overall (10.40 mm min), with at least 7.64 mm of thread height.

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General shop information only — follow your drawing, tool maker's data and your quality system.