Marine Nylon Insert Lock Nuts - DIN 985 DIN 982 Vibration Resistant
Marine Nylon Insert Lock Nuts
Nylon insert lock nuts per DIN 985 / DIN 982 and ISO 7040 / ISO 7042 in Class 8 and Class 10, with nylon insert for vibration-resistant locking. Available from M3 to M36 in zinc plated, hot dip galvanized and stainless steel finishes.
What Are Nylon Insert Lock Nuts?
Anylon insert lock nut (also called nylon lock nut, nyloc nut or elastic stop nut) is a hex nut with a nylon ring insert pressed into the top end. When a bolt is threaded into the nut, the nylon insert deforms elastically around the bolt thread, creating friction that prevents the nut from loosening under vibration and dynamic loading.
Nylon insert lock nuts are widely used in marine applications where bolted joints are exposed to continuous engine vibration, wave impact and thermal cycling. They are the most common locking method for non-critical structural connections, deck equipment mounting and instrumentation fasteners on ships.
Standards and Dimensions
Nylon lock nuts are standardized in several international specifications. The most commonly referenced standards for marine supply are:
| Standard | Type | Height | Typical Use |
|---|---|---|---|
| DIN 985 | Thin nylon lock nut | Standard hex height | General purpose, light vibration |
| DIN 982 | Thick nylon lock nut | Taller than standard | Higher locking force, severe vibration |
| ISO 7040 | Prevailing torque thin type | Standard hex height | International equivalent of DIN 985 |
| ISO 10511 | Prevailing torque thin type | Standard hex height | International prevailing torque spec |
| ISO 7042 | Prevailing torque thick type | Taller (2× nominal) | International equivalent of DIN 982 |
| IFI-182 / IFI-183 | Type 1 / Type 2 | US inch series | US Navy and offshore platform spec |
Size Range and Materials
| Size Range | Thread | Nut Body Material | Insert Material | Property Class |
|---|---|---|---|---|
| M3 - M16 | Metric coarse | Carbon steel (C15/C22) | PA66 Nylon (zinc plated) | Class 8 |
| M3 - M36 | Metric coarse | Carbon steel (C35) | PA66 Nylon (hot dip galvanized) | Class 8 / 10 |
| M3 - M24 | Metric coarse | A2 stainless steel (AISI 304) | PA66 Nylon | A2-70 |
| M3 - M24 | Metric coarse | A4 stainless steel (AISI 316) | PA66 Nylon | A4-80 |
| #4 - 1-1/2" | UNC / UNF | Carbon steel | PA66 Nylon (zinc plated) | Grade 5 / Grade 8 |
Temperature Limits
The nylon insert limits the operating temperature range of these nuts:
- Standard nylon (PA66): -40°C to +120°C continuous service
- High temperature nylon (PA66 + glass fiber): -40°C to +150°C continuous service
For marine engine room applications where service temperature exceeds 120°C, nylon lock nuts should not be used. Instead, specify all-metal prevailing torque nuts (ISO 2320 / ISO 7719) or mechanical locking devices.
Surface Treatment
Carbon steel nylon lock nuts are supplied with the following finishes for marine environments:
- Zinc plated per ISO 4042 - standard finish for indoor marine and deck equipment
- Hot dip galvanized per ISO 10683 - for hull structure and external marine exposure
- Zinc flake coating per ISO 10683 - for high strength bolt assemblies requiring controlled friction
- Stainless steel (A2/A4) - no additional coating required, naturally corrosion resistant
For petrochemical tanker applications where chloride exposure is high, A4 stainless steel (AISI 316) nylon lock nuts are recommended.
Quality Control
All nylon insert lock nuts are tested per ISO 2320 or DIN 267 Part 12 for prevailing torque performance:
- Prevailing torque test (first 5 engagements)
- Nylon insert concentricity check
- Proof load test per ISO 898-2
- Dimensional inspection per ISO 4759-1
- Surface coating thickness verification
Each batch is supplied with full material and test certificates. Third party inspection by DNV, ABS, LR or SGS can be arranged upon request.
Applications on Ships and Offshore
- Deck equipment: Instrument panels, control boxes and small equipment mounting
- Engine room: Auxiliary equipment, pipe support brackets and non-critical flange connections
- Hull structure: Interior panel fastening, cable tray supports and insulation mounting
- Petrochemical tankers: Instrumentation connections and sampling point fasteners (A4 grade)
- General marine: Non-critical locking applications where vibration resistance is required
Frequently Asked Questions
DIN 982 has a taller body (approximately double the nominal height) than DIN 985, which contains a longer nylon insert and provides higher prevailing torque. DIN 982 is used where stronger locking force is needed, such as severe vibration or safety-critical connections. DIN 985 is the standard choice for general marine applications.
Nylon lock nuts can typically be reused up to 5 engagements while maintaining effective prevailing torque, per ISO 2320 testing criteria. However, for marine safety-critical applications, it is recommended practice to replace nylon lock nuts after each dismantling to ensure reliable locking performance.
Standard PA66 nylon inserts are rated for continuous service up to 120°C. For applications above 120°C (such as engine exhaust systems or high temperature steam lines), use all-metal prevailing torque nuts per ISO 7719 instead, which can withstand temperatures up to 800°C depending on material grade.
Yes. A4 stainless steel (AISI 316) nylon lock nuts are available from M3 to M24. These are the preferred choice for saltwater exposure environments, petrochemical tanker applications and any installation where chloride corrosion resistance is critical.
For marine nylon lock nut inquiries, contact our engineering team:
Email: sales@sinofastener.com
Website: www.sinofastener.com
