Nyloc Self-Locking Nut - Secure & Reliable Fastening Solution
Product Introduction
Twenty years of exporting fasteners has taught us one thing about nyloc nuts: they get specified for a reason, and they fail for a reason. Usually the reason isn't the nut. It's the wrong grade, the wrong finish, or a cheap copy with a collar that's pressed in instead of locked in.
So here's the honest version of how ours works. The top of the nut carries a ring of polyamide 66 — engineering nylon, the real stuff. Its inner diameter comes off the machine slightly smaller than the pitch diameter of the bolt it's going to meet. When you drive the nut on, the collar doesn't get cut by the thread. It deforms elastically, wrapping over the thread profile, and that squeeze creates radial pressure on the flank. That's prevailing torque: resistance that exists independent of how hard you torqued the joint.
That last point matters more than people think. A standard nut holds only because the bolt is stretched in tension. Vibration, settling, thermal cycling — any of it can bleed that tension off, and then the nut walks. The nylon collar never relies on tension. It's gripping the thread from the moment it's on, so shock and cyclic load have nothing to work against.
You get the clamp load from the steel threads. You get the locking from the nylon. Two jobs, one part, zero extra components. No washers to forget on the line, no pins to align, no liquid thread-lock to cure and re-apply. Simpler inventory, faster assembly, fewer callbacks. Buyers in Chile, Peru and Brazil know this part as the tuerca autofrenante or porca autotravante — same nut, same standard, same honest behavior.
Full Specification
| Parameter | Value | Note |
|---|---|---|
| Primary standard | DIN EN ISO 7040 (style 1) | Prevailing torque hex nut, non-metallic insert |
| Related standards | ISO 10511 / ISO 10512 / ISO 2320 / ISO 898-2 | Thin nuts, fine pitch, functional properties, mechanical properties |
| Thread tolerance | 6H | Metric ISO coarse pitch |
| Locking insert | Polyamide 66 (PA66) | Colour per grade / OEM spec |
| Working temperature | Max 121°C (250°F) | Low end approx. -40°C, confirm per grade |
| Locking torque | Per ISO 2320 | First run-on / prevailing torque acceptance limits |
| Reusability | Conditional | FAA AC 43.13-1B; replace in safety-critical joints (USAF T.O. 1-1A-8) |
| Vibration resistance | High | Friction lock independent of clamp load |
| Proof stress (carbon steel) | 520 / 600 / 800 / 1040 MPa | Classes 5 / 6 / 8 / 10 per ISO 898-2 |
| Stainless grades | A2-70 / A4-70, A4-80 on request | A2 = 304, A4 = 316 |
| Aerospace reference | NASM 25027 | 250°F / 450°F / 800°F classes |
Assembly Notes
- Tightening torque = joint clamp torque + the prevailing torque the collar consumes. Calculate per ISO 898-2 / VDI 2230 and verify by test on the actual joint — don't trust a generic chart for a critical joint.
- Don't re-use a nut whose prevailing torque has dropped below the ISO 2320 minimum after repeated assemblies.
- Pellet-type nylon inserts lock noticeably weaker than a full nyloc collar ring. If the drawing says nyloc, don't accept a pellet substitute.
Size Chart
Standard range — 6.3 mm diameter (12 mm drill)
Dimensions per DIN EN ISO 7040 (tabular data according to DIN 982). h = overall height including the protruding nylon collar; m = height of metal nut body. Typical production range M3–M36, coarse thread; sizes beyond the table on request. Verify critical dimensions against the official standard text before production. |
Surface Finishes & Corrosion Protection
| Finish | Typical Use | Note |
|---|---|---|
| Electroplated zinc (blue / white / yellow passivation) | Indoor & mild environments | Most common commercial finish |
| Zinc-nickel (ZnNi) | Automotive underbody, higher salt exposure | Better cathodic protection |
| Zinc-flake (Dacromet / Delta-MKS / Geomet) | High-corrosion, torque-critical joints | Recommended for coastal / tropical service |
| Stainless steel (A2 / A4) | Marine, chemical, food contact | No coating required |
Pain Points & Solutions
| Pain point you told us about | What's really going on | How we solve it |
|---|---|---|
| "We re-tighten the screen deck every shift." | Standard nuts lose clamp load under vibration; once tension drops, the nut walks off. | Nyloc prevailing torque holds independent of clamp load. Class 8 for heavy decks; we send ISO 2320 run-on torque values with the batch so your team knows what "tight" feels like. |
| "The last lot we bought — the nylon ring fell out after one use." | Cheap copies use a pressed-in pellet or low-grade nylon. First assembly breaks the retention. | Full PA66 collar ring, mechanically retained in the nut body. Every batch gets a sample torque test before packing. |
| "Our spec says galvanized, the supplier said impossible." | They meant hot-dip galvanizing — 450°C melts the collar. Many buyers don't know the difference. | We supply the right answer: zinc electroplating, ZnNi, or zinc-flake (Dacromet / Geomet). If HDG-class protection is truly mandatory, we tell you straight — and quote an all-metal ISO 7042 nut instead. |
| "Rust within months, and we're 2 km from the sea." | Plain zinc can't survive coastal salt air; galvanic coupling between stainless and coated steel makes it worse. | A4 stainless or zinc-flake on the steel variant, with the galvanic isolation note in our tech sheet. We've done this for concentrator plants on the Chilean coast. |
| "The drawing says DIN 985, nobody stocks it." | DIN 985 was superseded by DIN EN ISO 7040. Old drawings all over Latin America still carry the old number. | Same geometry, current standard. We build to ISO 7040 and note the equivalent designation on your certificate — auditors accept it, your storekeeper finds it. |
| "Our ISO audit needs documents, the import needs papers." | Fastener imports into the region stall on missing certs and test reports. | Full documentation pack: material certificates, batch test report, declaration of conformity, packing list formats your customs broker knows. |
Applications
-
South American industry is where this nut earns its keep — vibrating, dusty, salty, and far from the nearest spare parts shelf. Here's where our nyloc nuts go to work:
- Mining & minerals — Chile, Peru, Colombia: screen decks, crusher liners, conveyor idler frames. Constant vibration plus dust that finds every unsealed thread. Class 8 with zinc-flake for coastal concentrators.
- Agriculture & agri-machinery — Brazil, Argentina: tractor implements, PTO guards, hydraulic bracket mountings. Field work means shock loads, mud, and no time for re-torquing every shift.
- Automotive & bus fleets: suspension links, brake and steering brackets — produced on our IATF 16949 line.
- Food & beverage processing: A4 stainless in washdown zones, where hygiene means aggressive cleaning chemicals every night.
- Construction & steel structures: secondary joints, handrails, cable trays — non-critical positions that still need to stay tight for years.
Selection rule. Use nyloc where vibration loosening is the failure mode and temperatures stay below 121°C. Where prevailing torque must be held at high temperature or under repetitive disassembly, select an all-metal prevailing-torque nut (ISO 7042) or a flange-nut system.
Why Work With Us?
- Own factory, 20+ years on fasteners. We don't trade these parts — we make them, from cold heading to final torque test.
- Certifications that survive an audit: IATF 16949 + ISO 9001 quality systems, CE, SGS and ROHS certificates on file. Your QA team can stop asking.
- Batch traceability: heat numbers, material certs, and ISO 2320 prevailing-torque verification on the batch test report — on request, before shipment.
- Standards we build to: DIN, ISO, ANSI, ASTM — whatever your drawing says, including legacy designations like DIN 985 on the same part.
- Export packing that survives the port: moisture-barrier cartons, labeled per your spec, palletized for container loading.
- South America logistics experience: we ship to Callao, Santos, Valparaíso and Buenos Aires regularly — documentation formats your customs broker actually recognizes.
These aren't hypothetical. Every one of these came from a customer who was losing money before they called us.
FAQ:
Q1: What is a nyloc self-locking nut?
A nyloc nut — also written nylock — is a hex nut with a polyamide (nylon) collar fused into its top end. In Spanish-speaking markets it's the tuerca autofrenante; in Brazil, the porca autotravante. The collar does the locking, the steel threads carry the load. That's the whole design.
Q2: How does the nylon collar actually lock the nut?
The collar's inner diameter is machined slightly smaller than the thread pitch diameter. As the nut runs onto the bolt, the nylon deforms elastically over the thread profile — it doesn't get cut, it squeezes. That radial squeeze creates friction that resists rotation on its own, regardless of clamp load. That's what prevailing torque means: resistance that's always there, not just when the joint is tight.
Q3: What temperature can a nyloc nut handle?
Keep nyloc service below 121°C (250°F). Past that, the PA66 collar softens and the locking degrades permanently — it's a one-way trip, not a reversible dip. Low end is roughly -40°C depending on grade. If your joint runs hotter, switch to an all-metal prevailing-torque nut like ISO 7042.
Q4: Can you reuse a nyloc nut?
Yes — within limits. The FAA's AC 43.13-1B permits reuse while the prevailing torque stays inside spec, and ISO 2320 gives the acceptance values. Practical rule: if the nut still feels tight on the bolt by hand and the collar is intact, it's usually fine for non-critical joints. In safety-critical positions — suspension, steering, anything that holds a person — replace it. Don't argue with the checklist on that one.
Q5: What torque should I apply?
The tightening torque you calculate for the joint, plus the prevailing torque the collar consumes. In practice: torque = joint clamp torque + prevailing torque, verified by test on the actual joint. We provide run-on and prevailing torque values per ISO 2320 with every batch on request. If your engineer works to VDI 2230, the same numbers fit.
Q6: Nyloc vs all-metal lock nut: which one do I need?
Nyloc wins on price, gentleness to the bolt thread, and reusability at normal temperatures. All-metal (ISO 7042) wins above 121°C, in hot-dip-galvanized assemblies, and where the nut gets cycled on and off repeatedly with high prevailing torque. For a vibrating screen at 60°C, nyloc. For an engine manifold at 300°C, all-metal. Match the joint, not the habit.
Q7:Why can't I hot-dip galvanize a nyloc nut?
Hot-dip runs at about 450°C. Polyamide 66 melts well below that. Send a nyloc nut through the galvanizing bath and you get a zinc-coated nut with a burned collar and no locking — worse than a plain nut, because nobody notices until it's in service. If your spec demands HDG-class protection, use zinc-flake (Dacromet, Geomet), ZnNi, or switch to an all-metal lock nut.
Q8: Is DIN 985 the same as ISO 7040?
Essentially yes. DIN 985 was the old German designation for nylon-insert hex nuts; it's been superseded by DIN EN ISO 7040 (style 1), with ISO 10511 for thin nuts. Old drawings still say DIN 985 or DIN 982 all over Latin America. We build to the current standard and note the equivalent designation on your certificate — same geometry, same dimensions.