Nylon insert lock nut

01

Choose the standard, size and property class

ISO 7040 specifies prevailing-torque hexagon regular nuts with a non-metallic insert for threads M3 to M36, product grade A up to M16 and grade B above M16, in property classes 5, 8 and 10. [1]

ISO 2320 specifies the functional properties of prevailing-torque steel nuts, all-metal and non-metallic insert types, tested at +10 to +35 °C, with a combined test for prevailing torque and torque/clamp force; it covers ISO metric coarse threads M5 to M39 and fine threads M8 × 1 to M39 × 3 with mechanical properties to ISO 898-2, and notes actual prevailing torques in use can vary from laboratory values. [2]

Haiyan Bolt lists DIN 985 nylon insert nuts with UNC and UNF threads, metric M5 to M33 and inch 1/4 to 2 1/4 in, in carbon, alloy and stainless steels (201, 304, 316), brass and aluminium alloy, with SAE classes, ASTM A194 2H and metric classes 4 to 10. [3]

Give the supplier the standard (ISO 7040, DIN 985 or inch), thread and size, property class or grade, material, finish, service temperature, quantity, packaging and any prevailing-torque test requirement.

02

Check service temperature, reuse and finish

ISO 2320 notes that non-metallic insert nuts meeting it are used in applications from −50 °C to +120 °C, while all-metal prevailing-torque nuts are used from −50 °C to +150 °C, and warns that temperatures outside the test range can affect properties. [2]

Haiyan Bolt explains that the nylon ring is compressed as the nut is run on and presses radially on the bolt thread to create the friction that resists loosening, and that "in many cases, Nylon Insert Nuts can be reused" if the insert and body are undamaged; it lists finishes from plain, black oxide and zinc to hot-dip galvanised, nickel, chrome, Dacromet and Geomet. [3]

Editorial calculation: the −50 to +120 °C insert range is −58 to +248 °F; above +120 °C an all-metal prevailing-torque nut (to +150 °C, 302 °F) is the listed alternative. [2]

03

Compare what suppliers offer

The suppliers linked to this page list nylon insert or locking nuts; their cards link to the pages reviewed.

Ask any supplier for the standard and drawing, property class and proof-load results, prevailing-torque test results to ISO 2320 or the relevant inch standard, insert material and temperature rating, finish and thickness, and packaging.

04

Weigh the nylon collar's 250 °F limit against all-metal locknuts

NASA's Fastener Design Manual (Reference Publication 1228, Richard T. Barrett, Lewis Research Center, March 1990) describes the nylon locking collar nut as a fiber or nylon washer mounted in the top of the nut, with an interference fit that binds on the bolt threads and gives some sealing against gas and moisture leakage. It names the approximate 250 °F temperature limit of the collar as the limiting feature of this nut. [4]

The manual gives the same approximate 250 °F maximum operating temperature for a nylon pellet set in the nut threads, and adds that the pellet will be damaged quickly by reassembly. For the deformed-thread all-metal locknut it says the temperature range is limited only by the parent metal, its plating, or both, and that the nut can be reused approximately 10 times before it has to be discarded for loss of locking capability. On finishes, it says zinc melts at 785 °F but has a useful service temperature limit of 250 °F, and that its corrosion-inhibiting qualities degrade above 140 °F. [4]

Editorial calculation: 250 °F = (250 − 32) × 5/9 ≈ 121 °C, in line with the +120 °C insert limit noted in ISO 2320 [2]; 140 °F = (140 − 32) × 5/9 = 60 °C. Editorial note: the manual is a 1990 design guide, not a product specification; ask the supplier for the insert material and its rated temperature, and for an all-metal prevailing-torque nut where the joint runs hotter.

05

Trace what defines the nut

This is a functional reference built from the sources cited; it is not one maker's specification.

06

Fill the specification fields with values for your order

A nylon insert lock nut quotation needs values for your joint. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.

07

Send the standard, size and service data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Standard: [ISO 7040; DIN 985; inch]
Thread: [M size; pitch; UNC/UNF]
Class: [5; 8; 10; grade]
Material: [steel; 304; 316]
Finish: [zinc; HDG; plain]
Service temperature: [°C]
Documents: [proof load; prevailing torque test]

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