Nuts · DIN 985
DIN 985 Nylock Nut
The DIN 985 Nylock Nut is a prevailing-torque locking nut designed to resist loosening under vibration and dynamic loads. Accurate Fastners manufactures these nuts in stainless steel grades SS 304 and SS 316, cold forged to the DIN 985 standard across M4–M20 diameters.
- Standard
- DIN 985
- Grades
- 304 / 316
- Size
- M4 – M20
- Length
- —
Overview
What is the DIN 985 Nylock Nut?
DIN 985 defines a low-profile hexagon nut fitted with a nylon insert at one end of the nut body. When a bolt or threaded stud is driven through, the nylon insert deforms slightly around the thread flanks, generating a frictional resistance that opposes self-loosening. This prevailing-torque action means the nut does not rely solely on clamping force to stay in position, making it a widely used choice in assemblies subject to vibration, thermal cycling or intermittent loading.
Accurate Fastners produces DIN 985 Nylock Nuts by cold forging, a manufacturing process that shapes the hexagonal body from stainless steel rod stock without removing material by cutting. Cold forging typically refines the grain structure of the metal and produces consistent dimensional geometry across the batch. The nylon insert is seated in a recessed collar at the top of the nut and is mechanically retained rather than adhesively bonded, keeping it in place during handling and assembly.
The nut presents a standard external hex drive, allowing it to be installed or removed with conventional spanners and socket tools. Its low-profile body follows the DIN 985 height specification, which is shallower than a full-height DIN 934 nut, making it suitable where axial space is restricted. Accurate Fastners subjects these nuts to quality checks during procurement and at delivery, consistent with the company's quality control practice across its fastener range.
In Depth
Product description
Construction and Geometry
The DIN 985 Nylock Nut comprises a cold-forged hexagonal body with a metric internal thread and a nylon insert collar integrated at the top face. The body height is lower than a standard hex nut, as prescribed by the DIN 985 dimensional standard. The cold-forging process imparts close dimensional consistency across the hex flats and thread pitch, which supports reliable engagement with mating bolts and torque tools.
The nylon insert protrudes slightly into the threaded bore and has an unthreaded central aperture. As the bolt progresses through the metallic thread and into the nylon zone, the insert grips the thread without being pre-threaded itself. This design keeps the locking action independent of the metallic thread condition and allows the nut to be reused a limited number of times, though repeated cycling gradually reduces the insert's prevailing torque.
Functional Behaviour in an Assembly
During installation, torque is applied to the hex body until the joint reaches the desired clamp load. As the bolt tip enters the nylon insert, additional resistance is felt — this is the prevailing torque generated by the insert deforming around the thread. The resistance remains present even if the joint loses some clamp load, which is why DIN 985 nuts are commonly specified in assemblies where vibration may otherwise allow a plain nut to rotate back.
In service, the nylon insert maintains contact with the bolt thread flanks, providing a continuous frictional restraint. Unlike locking methods that depend on deformation of the metallic body, the nylon insert approach does not permanently alter the bolt thread, meaning the bolt remains reusable. However, the insert may be affected by elevated operating temperatures over time, and this should be factored into the selection process for high-temperature environments.
How It Differs from Similar Fasteners
A DIN 985 Nylock Nut is sometimes compared to a DIN 982 nut. The key dimensional difference is body height: DIN 985 specifies a low-profile (thin) nut, while DIN 982 specifies a full-height body. Both carry a nylon insert and serve a similar prevailing-torque function, but the lower profile of the DIN 985 variant makes it preferable in compact assemblies where a full-height nut would not fit within the available clearance envelope.
Compared with a plain DIN 934 hex nut secured by a separate spring or flat washer, the DIN 985 integrates the locking feature within the nut itself, reducing the component count in an assembly. Unlike all-metal prevailing-torque nuts — which achieve locking by distorting the metallic thread form — the DIN 985 preserves the integrity of the bolt thread, which may simplify maintenance and inspection in accessible assemblies.
Material & Grade
Material and grade information
- SS 304
- SS 316
Accurate Fastners supplies DIN 985 Nylock Nuts in SS 304 and SS 316. SS 304 is an austenitic stainless steel containing approximately 18% chromium and 8% nickel. It offers good general corrosion resistance in many environments and is commonly used in food and beverage machinery, LED lighting structures and water treatment equipment. Its cost is generally lower than SS 316, which may be relevant when specifying larger quantities across M4–M20 sizes.
SS 316 incorporates molybdenum in addition to chromium and nickel, which is generally understood to improve resistance to chloride-containing and mildly aggressive chemical environments compared with SS 304. For applications in pharmaceutical machinery or environments where cleaning agents or process fluids are present, SS 316 may be worth considering. Grade selection should be discussed with the Accurate Fastners sales team based on the specific operating environment and mating fastener material.
Grades shown are those documented for this product in the Accurate Fastners brochure. General material notes are guidance only; confirm grade selection for your environment.
Technical Data
Technical specifications
| Product type | Nut – DIN 985 Nylock Nut |
|---|---|
| Material | Stainless steel |
| Material grade | SS 304, SS 316 |
| Applicable standard | DIN 985 |
| Nominal diameter / size | M4 – M20 |
| Thread type | Metric internal thread |
| Head / form | Low-profile hexagon with nylon insert |
| Drive / tightening | External hex |
| Manufacturing process | Cold forged |
Sizes
Available sizes
Documented size range
M4 – M20
Documented length range
Not applicable
Individual sizes within the documented range, thread pitches and lengths are confirmed at quotation stage.
Applications
Industrial applications
RO Water Purifier Assemblies
DIN 985 Nylock Nuts in SS 304 may be used to secure panel frames and filter housings in RO water purifier units, where moisture exposure makes a corrosion-resistant, vibration-resistant nut a practical choice.
Submersible Pump Enclosures
Pump casings and motor end covers in submersible pump assemblies can generate significant vibration. A prevailing-torque nut such as the DIN 985 may help maintain joint integrity in such dynamic conditions.
Solar Energy Mounting Structures
Solar panel racking systems use multiple fasteners across exposed structural joints. DIN 985 Nylock Nuts in SS 304 or SS 316 may be considered for connections where wind-induced vibration is a factor.
Pharmaceutical Machinery Frames
Equipment frames and guard panels in pharmaceutical machinery may benefit from SS 316 DIN 985 nuts, where resistance to cleaning agents and hygienic material selection are relevant considerations for the specifier.
LED Lighting Fixtures and Enclosures
Lightweight LED luminaire housings and driver enclosures commonly use M4–M8 fasteners. DIN 985 nuts in SS 304 may provide secure retention in assemblies subject to intermittent mechanical vibration.
Featured for: Submersible Pump
Features & Selection
Features and selection considerations
Design features
Cold-Forged Body
The hex body is cold forged from stainless steel, a process that typically produces consistent dimensional geometry and a uniform grain structure across the production batch.
Integrated Nylon Insert
A mechanically retained nylon insert at the top of the nut generates prevailing torque against the bolt thread, providing locking action without requiring secondary locking components.
Low-Profile Hex Form
The DIN 985 body height is lower than a full-height nut, making these nuts suitable for joint configurations where axial space between the bearing surface and thread end is limited.
M4–M20 Size Range
Available across a broad metric diameter range from M4 to M20, supporting specification across panel, frame and structural joint applications within a single product family.
Standard External Hex Drive
The hex-drive format is compatible with standard spanners, ratchet sockets and torque wrenches, requiring no specialist tooling for installation or removal in the field.
Before you order
Thread Diameter and Pitch
Confirm the nominal diameter (M4–M20) and pitch of the mating bolt before ordering. Standard metric coarse pitch is typical for DIN 985, but verify your assembly drawing or existing fastener specification to avoid mismatches.
Grade Selection by Environment
Choose SS 304 for general indoor or low-moisture environments and SS 316 for assemblies exposed to chemicals, cleaning agents or elevated chloride conditions. Consult Accurate Fastners' sales team if the environment is uncertain.
Mating Fastener Compatibility
The DIN 985 nut should be paired with a bolt of compatible grade and thread standard. Using mismatched grades or thread systems may compromise joint performance. Accurate Fastners can advise on compatible bolt and washer supply.
Quantity and Documentation
For bulk orders, confirm required quantities and whether material test reports or quality documentation are needed. Accurate Fastners performs quality checks at procurement and delivery stages, which may support your incoming inspection process.
FAQs
Frequently asked questions
What standard do these Nylock Nuts comply with?
These nuts are manufactured to the DIN 985 standard, which specifies dimensional requirements for low-profile hexagon nuts with a nylon insert. Accurate Fastners' broader fastener range is also produced in compliance with IS, BS and DIN standards as applicable.
Which stainless steel grades are available?
Accurate Fastners supplies DIN 985 Nylock Nuts in SS 304 and SS 316. SS 304 is suitable for many general applications, while SS 316 is typically considered where improved resistance to chloride or chemical environments may be required.
What size range is offered?
DIN 985 Nylock Nuts are available from M4 to M20. If your application requires sizes outside this range, contact the Accurate Fastners sales team to discuss whether alternative products or special supply can be arranged.
Can the nylon insert be used at high temperatures?
Nylon inserts are generally understood to have an upper temperature limit beyond which the insert may soften and lose its prevailing-torque effectiveness. For elevated-temperature assemblies, discuss your operating conditions with the sales team before specifying this nut type.
Are matching bolts and washers available from Accurate Fastners?
Accurate Fastners manufactures and supplies a wide range of fasteners including bolts, washers and related hardware. Contact the team to enquire about compatible components in matching grades and standards for your assembly.
How can I request a quotation or place an order?
You can submit your requirements via the enquiry form on the website, email the team directly at export@accuratefastners.com, or reach out via WhatsApp. Please include the diameter, grade, quantity and any documentation requirements to receive an accurate quote.
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