All Metal Prevailing Torque Nuts

Trojan Special Fasteners Ltd routinely manufactures prevailing torque nuts to customer's requirements in multiple material and finish combinations.

Nylon insert nuts are a type of prevailing torque nut and are found here.

All metal prevailing torque nuts come in various different forms. These incorporate a locking feature that increases friction between the nut and it's mating part. This means that you have to apply a greater force to assemble the nut and also to remove it - ultimately this means that the nuts do not loosen with vibration. Additionally, these are all metal which means that they can be used in applications where excessive temperatures exist or where certain chemicals are used. Typically, they can be used up to 750 degrees C (or about 1400 Fahrenheit).

These type of nuts are typically reusable a number of times, but it has to be noted that subsequent removals reduce the 'prevailing torque' so they become less effective the more often they are removed and reapplied.

The greater the degree of deformation, the higher the amount of application and removal torque is required. The ISO 898 standard defines the amount of prevailing torque needed for metric fasteners and the IFI 100/107 standard defines the prevailing torque required for unified threads. No standard exists for the BSW and BSF threads.

It is recommended that these nuts are applied towards the ends of a mating part because the further they travel the higher the risk of damaging threads. Also, high strength all metal prevailing torque nuts must not be used low strength mating parts because the hard nut will act like a die and destroy the male threaded part.

Please note that Trojan Special Fasteners Ltd does not manufacture patented and trademarked items, but we have manufactured similar items based on customer drawings that utilise some of the prevailing torque locking mechanisms shown below; the following are only given as examples of all metal prevailing nut forms.

The types of all metal prevailing typically rely on deforming the nut in one way or another, the following forms exist:

Elliptically deformed threads

These nuts are known as automation lock nuts, autolock nuts, conelock nuts, crownlock nuts, philidas mkv or mk5 nuts, stover nuts and unitorque nuts. They typically have a conical section which is deformed at two points. In the diagram below you can see that the nut is 'pinched' at the conical section in two points. The threads are therefore elliptically deformed. This pinching creates an increased friction between threads and thus creates the prevailing torque action. This type of nut is not reversible and cannot be mounted cone-first.

Ultimately the above three types serve the same purpose and the only difference is in how the conical section is deformed. A further modification to this type of nut is one in which the cone is deformed into an obround triangle, which means that it is pinched in three places:

Sometimes a collar can be provided at the top, rather than a conical surface, which is then deformed across the collar height, forcing elliptical deformation of threads:

Alternatively, the small section of the top of the nut can be deformed in two places, without needing a cone or collar as follows:

Another way of providing prevailing torque is to deform the threads of a nut from the top, without a cone. They are also known as tri lock or top lock nuts These are non reversible nuts. The following forms exist:

Typically, the top first or second threads are deformed - this deformation increases friction and thus prevailing torque - which stops the nut from loosening under vibration.

Other proprietary forms of all metal prevailing torque lock nuts exist in the market place, the following all utilise axial slots and deformation of the nut to provide a prevailing torque locking feature:

Philidas Industrial Nuts

Philidas Industrial Flange Nuts

Philidas Turret Nuts

Philidas Turret Flange Nuts

Aerotight Nuts

Aerotight Flanged Nuts

Split nuts or Gland nuts

Binx Nuts

The above forms have axial slots either in a crown sections on one side (philidas and aerotight types) or in the actual body of the nut at 0.5h or 0.66h as in the case of the above split nuts.

These nuts are physically deformed so that the displaced sections cause axial deformation of the thread. Once they are applied, they are forced back to their original position which creates prevailing torque.

Other methods to provide all metal prevailing torque exist, so please note this page is not exhaustive.

In addition to standard preferred sizes, we also manufacture non preferred and non standard or special thread and nut forms and sizes.

We can manufacture to the following specifications:

In addition to machining all metal prevailing torque locking nuts to your dimensions, sample or drawing, we can machine them to the following specifications:

Standard Description
ASME/ANSI B18.16.3M All metal prevailing torque hexagon flange nuts
ASME/ANSI B18.16.3M All metal prevailing torque hexagon nuts
DIN 6925 All metal prevailing torque hexagon nuts
DIN 6927 All metal prevailing torque hexagon flange nuts
DIN 980 All metal prevailing torque hexagon nuts
EN 1664 All metal prevailing torque hexagon nuts
EN 1667 All metal prevailing torque hexagon nuts
IFI 100/107 Prevailing Torque Nuts
ISO 12126 All metal prevailing torque hexagon flange nuts
ISO 7042 All metal prevailing torque hexagon nuts, style 2
Standard Description
ISO 7044 All metal prevailing torque hexagon nuts
ISO 7719 All metal prevailing torque hexagon nuts, style 1
ISO 7720 All metal prevailing torque hexagon nuts, style 2
NF E25-410 All metal prevailing torque hexagon nuts, style 1
NF E25-411 All metal prevailing torque hexagon nuts with slots - HFR
NF E25-414 All metal prevailing torque hexagon flange nuts
NF E25-420 All metal prevailing torque hexagon flange nuts, style 2
NF E25-421 All metal prevailing torque hexagon flange nuts, style 1
NF E25-422 All metal prevailing torque hexagon flange nuts, style 2
NF E25-507 All metal prevailing torque hexagon flange nuts

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