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Technical datasheet DIN 985 / ISO 10511 — Prevailing torque hexagon nut, nylon insert

Reference only — for design, verification or contractual purposes refer to the current issue of the original standard. MF Fastener Industries LLC · sales@mfindllc.com · +971 6 767 2469 · mfindllc.com

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Dimensional datasheet

DIN 985 nyloc nut

Hexagon nut with a nylon insert that grips the thread and resists loosening under vibration. Also called a nylon insert lock nut or Nyloc. The common locking nut for machinery and general assembly.

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d nominal thread diameters width across flatsm nut height including insert

Dimensions

millimetres

Metric coarse thread, tolerance 6H. The nut is taller than a plain DIN 934 because of the insert — check clearance where the projection above the nut is tight.

Size	Pitch	s — across flats	Spanner size	m — height	DIN 934 height
M6	1.00	10.00	10 mm	6.0	5.2
M8	1.25	13.00	13 mm	8.0	6.8
M10	1.50	16.00 (DIN 17.00)	16 mm / 17 mm	10.0	8.4
M12	1.75	18.00 (DIN 19.00)	18 mm / 19 mm	12.0	10.8
M16	2.00	24.00	24 mm	16.0	14.8
M20	2.50	30.00	30 mm	20.0	18.0
M24	3.00	36.00	36 mm	24.0	21.5

Temperature limit is the nylon, not the steel

The insert softens and loses its grip above about 120 °C. In sustained heat the nut becomes an ordinary nut with no locking function, and nobody notices until something comes loose.

For hot applications use an all-metal prevailing torque nut, a castle nut with a split pin, or a serrated flange nut.

Treat as single use

The insert is deformed by the thread on first use. Reusing a nyloc gives a much lower prevailing torque, and after a few cycles it is no longer a locking nut.

The usual site rule is one use only. Order spares rather than reusing.

The bolt must project through the insert

The thread has to reach fully into the nylon for the nut to lock. A bolt that stops short of the insert leaves a nut that turns freely.

Allow at least two full threads beyond the top face of the nut.

Property classes

ISO 898-2

Class	Proof load stress	Pair with bolt class	Note
5	500 N/mm²	4.6, 5.6	General
8	800 N/mm²	8.8	The common commercial grade
10	1040 N/mm²	10.9	Available to order
A2-70 / A4-80	700 / 800 N/mm²	Stainless bolts	Insert still 120 °C limited

Class is marked on the nut face. Note that the insert limits temperature even on stainless nuts — the alloy has nothing to do with it.

Locking alternatives

selection

Option	Standard	Reusable	Temperature
Nylon insert	DIN 985 · ISO 10511	No	≤ 120 °C
All-metal prevailing torque	DIN 980 · ISO 7042	Limited	High
Serrated flange nut	DIN 6923	Yes	High
Castle nut and split pin	DIN 935	Yes	High
Wedge-lock washer pair	Proprietary	Yes	High

A plain washer under a nyloc adds nothing to the locking function. The insert does the work.

At a glance

Standard	DIN 985 · ISO 10511
Form	Hexagon, nylon insert, low profile
Thread form	Metric coarse, ISO 68-1
Tolerance	6H
Temperature limit	≈ 120 °C
Re-use	Not recommended
Tall version	DIN 982 · ISO 7040
Plain equivalent	DIN 934 · ISO 4032
All-metal locking	DIN 980 · ISO 7042

Supply

Imported and held in stock, sourced from established mills and supplied from our warehouse in Umm Al Quwain.

Anchor bolts, studs and plate washers are manufactured at our own plant. This item is not.

Materials and finish

Carbon steel	Plain, zinc plated
Stainless	A2-70, A4-80
Hot-dip galvanized	Rarely — the insert does not tolerate the bath
Certification	Mill certificate on request

Testing

Dimensional and thread inspection is carried out in our own plant on calibrated instruments. Tensile, hardness and chemical testing is carried out by independent UAE-accredited laboratories.

Reference only

This datasheet is published for reference. Dimensions and property values are reproduced in good faith from published standards, but for design, verification or contractual purposes always refer to the current issue of the original standard.

If a figure here conflicts with the standard, the standard governs.

Need a quotation?

Send the size, class, finish and quantity. Tell us the service temperature if it is anywhere near 100 °C.