DIN 986 Hex Domed Cap Nuts with Non-Metallic Insert
DIN 986 hexagon domed cap nuts with non-metallic nylon insert, M4 to M20 — the acorn nut that locks by prevailing torque and closes the bolt end under a domed cover, with the collected per-size tables: pitches, d a, d w, e, h 1, h 2, m, m w, r and s.
Last updated: 2026-11
Specifications
DIN 986 is the domed cap nut with a lock built in: the classic acorn silhouette — a hex driving section, a cylindrical skirt and a domed cover that closes off the bolt end — combined with a non-metallic nylon collar, so the same prevailing-torque grip that keeps the nut on also removes the need for a separate lock washer under a cap. That combination matters where the exposed thread end is itself the problem: guarding requirements (no cut thread projecting past a nut), product-safety housings, food and conveyor equipment where an open thread collects debris, and appearance hardware. The dome costs height — the collected tables split the height into the threaded section h 1 and the overall domed height h 2 (e.g. 9.6 mm total at M4 against 35 mm at M20) with the domed radius r per size — so check the stack budget first. The tables run M4 to M20 with pitch options, d a, d w, e, h 1, h 2, m, m w, r and s, plus the source mass rows printed verbatim. Insert temperature limits, finishes and the thread run-out inside the dome are not printed by the collected specification and stay per RFQ.
| Standard | DIN 986 — hexagon domed cap nuts with non-metallic insert (locking acorn nuts) |
|---|---|
| Series | M4 – M20 (three source column groups; coarse and fine pitch options tabulated per size) |
| Tabulated geometry | Per size: pitch (coarse / Fine thread 1/2 as printed), d a, d w (min), e (min, 7.66–32.95 mm), h 1 threaded height (5.6–21 mm), h 2 overall domed height (9.6–35 mm), m (min), m w (min), domed radius r (2.5–10.8 mm), s (7–30 mm), source mass per 1000 units ≈ kg |
| Locking mechanism | Nylon collar prevailing torque — the cap locks itself; no separate lock washer under the skirt |
| Insert temp limit / finishes | Not tabulated by the collected specification — per RFQ (state duty temperature at quotation) |
| Attribute | M4 | M5 | M6 |
|---|---|---|---|
| P — Pitch — Pitch（Coarse thread） | 0.7 | 0.8 | 1 |
| Fine thread 1 | / | / | / |
| Fine thread 2 | / | / | / |
| d a — min | 4 | 5 | 6 |
| max | 4.6 | 5.75 | 6.75 |
| d w — min | 5.9 | 6.9 | 8.9 |
| e — min | 7.66 | 8.79 | 11.05 |
| h 1 — Nominal Size | 5.6 | 6 | 7.5 |
| max | 5.85 | 6.25 | 7.85 |
| min | 5.35 | 5.75 | 7.15 |
| h 2 — Nominal Size | 9.6 | 10.5 | 12 |
| max | 9.9 | 10.85 | 12.35 |
| min | 9.3 | 10.15 | 11.65 |
| m — min | 2.9 | 4.4 | 4.9 |
| m w — min | 2.32 | 3.52 | 3.92 |
| r — max=nominal size | 2.5 | 3 | 3.5 |
| max | 2.7 | 3.5 | 4 |
| min | 2.3 | 2.5 | 3 |
| s — max=nominal size | 7 | 8 | 10 |
| min | 6.78 | 7.78 | 9.78 |
| per 1000 units ≈ kg | 1.4 | 1.55 | 3.3 |
| Attribute | M8 | M10 | M12 |
|---|---|---|---|
| P — Pitch — Pitch（Coarse thread） | 1.25 | 1.5 | 1.75 |
| Fine thread 1 | 1 | 1 | 1.5 |
| Fine thread 2 | / | 1.25 | 1.25 |
| d a — min | 8 | 10 | 12 |
| max | 8.75 | 10.8 | 13 |
| d w — min | 11.6 | 14.6 | 16.6 |
| e — min | 14.38 | 17.77 | 20.03 |
| h 1 — Nominal Size | 8.9 | 10.5 | 13.5 |
| max | 9.25 | 10.9 | 13.9 |
| min | 8.55 | 10.1 | 13.1 |
| h 2 — Nominal Size | 14 | 18.1 | 22.5 |
| max | 14.35 | 18.5 | 22.9 |
| min | 13.65 | 17.7 | 22.1 |
| m — min | 6.44 | 8.04 | 10.37 |
| m w — min | 5.15 | 6.43 | 8.3 |
| r — max=nominal size | 4.6 | 5.8 | 6.8 |
| max | 5.1 | 6.3 | 7.8 |
| min | 4.1 | 5.3 | 5.8 |
| s — max=nominal size | 13 | 16 | 18 |
| min | 12.73 | 15.73 | 17.73 |
| per 1000 units ≈ kg | 5.3 | 10.1 | 18.3 |
| Attribute | M14 | M16 | M20 |
|---|---|---|---|
| P — Pitch — Pitch（Coarse thread） | 2 | 2 | 2.5 |
| Fine thread 1 | 1.5 | 1.5 | 2 |
| Fine thread 2 | / | / | 1.5 |
| d a — min | 14 | 16 | 20 |
| max | 15.1 | 17.3 | 21.6 |
| d w — min | 19.6 | 22.5 | 27.7 |
| e — min | 23.35 | 26.75 | 32.95 |
| h 1 — Nominal Size | 15.5 | 16.5 | 21 |
| max | 15.9 | 16.9 | 21.5 |
| min | 15.1 | 16.1 | 20.5 |
| h 2 — Nominal Size | 26.4 | 27.5 | 35 |
| max | 26.8 | 27.9 | 35.5 |
| min | 26 | 27.1 | 34.5 |
| m — min | 12.1 | 14.1 | 16.9 |
| m w — min | 9.68 | 11.28 | 13.52 |
| r — max=nominal size | 7.8 | 8.8 | 10.8 |
| max | 8.8 | 9.8 | 11.8 |
| min | 6.8 | 7.8 | 9.8 |
| s — max=nominal size | 21 | 24 | 30 |
| min | 20.67 | 23.67 | 29.16 |
| per 1000 units ≈ kg | 26.1 | 37.1 | 111 |
Materials
- Body material and finish specified per RFQ; insert is non-metallic (nylon) per the standard — confirm duty temperature at quotation
Ordering & documentation
Documents
Shipments are backed by Mill Test Certificate (MTC), Dimensional Report, Salt Spray Test Report on request, with full batch traceability from raw material to finished product. Quality management follows the owner-confirmed compliance list: ISO 9001:2015, RoHS, REACH. Exact document sets are confirmed on the order.
Quotation
- The fastener family (DIN 986 Hex Domed Cap Nuts with Non-Metallic Insert) plus the standard designation from your drawing — DIN / ISO / JIS / ASTM / ANSI, or a drawing for custom parts.
- Size (diameter and length), thread type (metric or inch), property class or grade, and coating or finish.
- Quantity per size and your target delivery date.
- Destination country, and any required documents (for example a mill test certificate) so the quote includes them.
Sample & supply
Minimum order quantity is 10,000 pieces. Stock items run 3–7 days. Quantities or variants outside the standard range are confirmed at quotation.
Storage & shipping
Parts are packed for export and shipped factory-direct to buyers in Europe, Asia, the Americas and the Middle East. Store fasteners dry and protected until installation, and keep coated parts in their packaging until use; specific packing and preservation requirements can be stated on the order and confirmed at quotation.
Frequently asked questions
When does a DIN 986 cap nut replace a plain nut plus cover detail?
When the exposed thread end needs to disappear and the joint still needs a lock. A plain acorn nut closes the bolt end but offers nothing against back-off; a nylon-insert lock nut locks but leaves thread and load faces exposed. DIN 986 is both in one part: the collected tables carry the prevailing-torque geometry (m w per size, the nylon collar at the thread) together with the domed cover dimensions (h 2, domed radius r), so guarding, hygiene and appearance requirements are met without stacking two parts — and the dome itself adds height (h 2 is roughly double the threaded height h 1 per size), so verify the stack and the bolt projection: the thread must end inside the dome. If your duty temperature runs past the nylon collar's range, say so at RFQ — a high-temperature joint needs an all-metal lock, not this part.
What is the MOQ and lead time for this nut type?
The minimum order quantity is 10,000 pieces. Stock items ship in 3–7 days; non-stock items are confirmed at quotation. Common sizes in this nut type are widely stocked; confirm the exact schedule against quantity and size mix at quotation.
Request a Quote
Get factory-direct pricing from the manufacturer.
What to include in your inquiry
- ✓ Standard and property class (e.g. DIN 912, ISO 4762, class 8.8) — or a drawing for custom parts.
- ✓ Sizes, lengths and thread type (metric or inch).
- ✓ Quantity per size and your target delivery date.
- ✓ Destination country, plus any coating or finish requirement.
- ✓ Any documents you need with the shipment (e.g. mill test certificate) so the quote includes them.
- ✓ Your inquiry goes straight to the factory team by email and gets a reply within 24 hours.
- ✓ Factory-direct pricing
- ✓ Standard and custom specifications
- ✓ Factory-direct export to buyers in Europe, Asia, the Americas and the Middle East
- ✓ Full fastener family support