📐 Free Gage Block Calculator — no login. Open it →

← AskMachinist · Guides · Calculator · 🔎 Search

Nylon Insert Lock Nut Dimensions (ISO 7040, M3 to M36)

Guide · Updated October 28, 2026

ISO 7040 covers prevailing torque hexagon regular nuts with a non metallic (nylon) insert, the common nyloc nut in metric fixture and machine work. The steel body matches ISO 4032 style 1 nut sizes, with the nylon ring adding height. The table gives coarse pitch, width across flats s (wrench size), total height h max and min, metal height m min, width across corners e min and bearing face dw min. Values agree between the ISO 7040:2012 table, the Nufast ISO 7040 production drawing and the RC Fastener ISO 7040 spec sheet. ISO 7040:2025 revised the small M3 and M4 designs, and old DIN 982 nuts differ, so check your supplier for critical work.

Need an exact reference size?

Build any gage block stack with the free Gage Block Calculator. Free, no login.

Step by step

  1. Match the thread: Check diameter and pitch with a thread gage. This chart is coarse pitch M3 to M36, the regular height nut with a nylon ring.
  2. Pick the wrench: Across flats s matches ISO 4032 hex nuts: M6 10 mm, M8 13 mm, M10 16 mm, M12 18 mm. Older DIN 982 / DIN 985 nuts use 17 and 19 mm at M10 and M12.
  3. Check the height: Total height h max is the clearance you need over the bolt end and under a cover. Metal height m is the threaded steel part that carries load.
  4. Leave thread past the nut: Run at least 2 full threads past the nylon ring so the insert is fully engaged.
  5. Watch the heat: Nylon inserts are generally rated to about 120 C. Above that, use an all metal prevailing torque nut (ISO 7042).
  6. Reuse with care: Nylon loses grip each time. Replace a nyloc nut that spins on by hand or on critical joints.

ISO 7040 nylon insert lock nut dimensions (mm)

Columns: thread size, coarse pitch P, width across flats s (max, the wrench size), total height h max, h min, metal height m min, width across corners e min, bearing face diameter dw min. Grade A through M16, grade B above.

Wrench quick list

ISO 7040 wrench by thread: M3 5.5 mm, M4 7 mm, M5 8 mm, M6 10 mm, M8 13 mm, M10 16 mm, M12 18 mm, M16 24 mm, M20 30 mm, M24 36 mm, M30 46 mm, M36 55 mm. Same as an ISO 4017 hex head on the same thread.

ISO 7040 vs DIN 982 vs DIN 985

DIN 982 is the older regular height nyloc: M10 17 mm and 11.5 mm tall, M12 19 mm and 14 mm tall. ISO 7040 is 16 mm / 11.9 mm and 18 mm / 14.9 mm. DIN 985 (now ISO 10511) is the thin version, roughly a jam nut plus the ring. Hardware store nylocs are often still DIN sizes.

Worked example: bolt length for an M8 nyloc

Clamping a 10 mm plate and a 6 mm bracket with an M8 hex screw, two 1.6 mm ISO 7089 washers and an ISO 7040 nut: grip 16 + 3.2 = 19.2 mm, nut h max 9.5 mm, plus 2 threads at 1.25 mm = 2.5 mm. Total 31.2 mm, so pick an M8 x 35 and check that the end clears any cover.

Worked example: clearance under a guard

An M12 ISO 7040 nut stands up to 14.9 mm tall and is 20.03 mm across corners minimum. With 3 mm of thread past the nut and a 2.5 mm washer, leave about 21 mm under the guard and a 26 mm circle for the socket.

Common problems

FAQ

What wrench fits an M10 nyloc nut?

16 mm for ISO 7040. Many nuts sold as DIN 982 or DIN 985 are 17 mm at M10 and 19 mm at M12, so check the box.

What is the difference between ISO 7040 and DIN 985?

ISO 7040 is the regular height nut (similar to old DIN 982). DIN 985 (ISO 10511) is the thin, jam height nylon insert nut.

How many threads should stick out past a nyloc nut?

At least 2 full threads past the nylon ring so the insert is fully formed on the thread.

Can you reuse a nylon insert lock nut?

A few times on non critical work if it still needs a wrench to turn. Replace it when it spins on by hand.

Related guides and calculators

Build your stack in seconds

The free Gage Block Calculator finds the fewest-block combination for inch and metric sets, with wear blocks. No login.

Questions? Ask a machinist.

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