TUFF® · Nuts · New
Resists loosening under vibration and heat.
TUFF FS All-Steel Lock Nut · DIN 980 / ISO 7042 · tested to ISO 2320
The TUFF FS lock nut locks with metal, not plastic. Its all-steel locking zone grips the bolt thread, so the prevailing torque keeps the nut from backing off if preload drops. ISO 2320 covers all-metal lock nuts from −50 °C to +150 °C, against +120 °C for nylon-insert nuts.
Intended result: fewer loose nuts and less re-tightening on vibrating equipment. Made, heat-treated and lot-tested by Pioneer Nuts & Bolts.
Why buyers switch
- Locks without clamp load
- The locking torque does not depend on clamp load, so the nut resists backing off even if the joint loses some preload.
- Works in heat
- No nylon ring to soften. ISO 2320 covers all-metal lock nuts up to +150 °C (nylon-insert nuts: +120 °C). Higher temperatures by agreement.
- For vibrating equipment
- Used on screens, crushers, rail bogies, compressors and wind turbines.
- Pairs with high-tensile bolts
- Class 10 nut for 10.9 bolts, class 8 for 8.8, class 12 for 12.9 (ISO 898-2).
- Tested to ISO 2320
- Prevailing torque is checked at first fitting and at first and fifth removal, as ISO 2320 requires.
Key facts
- Type
- All-steel prevailing torque hexagon nut, no nylon insert
- Sizes
- M8 – M36 (ISO 7042 range to M36); other sizes to drawing
- Property classes
- 5, 8, 10, 12 (ISO 7042 / ISO 898-2)
- Standards
- DIN 980 / ISO 7042 · performance to ISO 2320
- Temperature
- −50 °C to +150 °C (ISO 2320)
- Finishes
- Plain, zinc electroplated (ISO 4042) or zinc flake (ISO 10683), to order
- Made by
- Pioneer Nuts & Bolts Pvt. Ltd. (TUFF®), India
FS lock nut against other locking methods
| Method | Locks by | Heat | Notes |
|---|---|---|---|
| TUFF FS all-steel lock nut | Steel locking zone grips the thread | To +150 °C (ISO 2320) | One part. Higher run-down torque than a plain nut; reuse limited (ISO 2320 checks five cycles) |
| Nylon insert nut | Nylon ring | To +120 °C (ISO 2320) | Nylon softens with heat and ages; not suited above +120 °C |
| Jam nut pair | Second thin nut | Yes | Two parts, extra fitting time, works loose if not set correctly |
| Spring washer | Washer spring force | Yes | Flattens under high-tensile preload; little locking |
General comparison of locking methods, based on published standards and test literature, not on tests of other makers' products. The joint engineer decides.
FS lock nut: questions
Can the FS lock nut be reused?
ISO 2320, the test standard for prevailing torque nuts, checks locking over five fit-and-remove cycles. Beyond that, reuse is not assured; fit a new nut when reassembling a critical joint.
Is it a replacement for nylon-insert nuts?
It can be, where the joint sees heat, solvents or long service and the engineer approves. An all-steel locking zone does not soften like nylon.
Which bolt should it be used with?
Match the nut class to the bolt: class 10 with 10.9 bolts, class 8 with 8.8 bolts (ISO 898-2).
New product. Locking performance depends on bolt, finish, temperature and joint; the order, datasheet and lot test certificate govern. Not design advice.
About the maker
- Fasteners since 1996Pioneer Nuts & Bolts Pvt. Ltd., brand TUFF®. Forging, heat treatment, machining and finishing in-house.
- 50 yearsMetallurgy and heat treatment, since 1976.
- IATF 16949:2016Certified quality management system.
- NABL labIn-house laboratory accredited by NABL to ISO/IEC 17025:2017 for the tests in its scope. Lots tested to the applicable standard.
- Japanese collaborationTechnical collaboration with Japanese fastener companies.
- 150+ testimonialsMore than 150 customer testimonials.