SAE J483 Low Crown Acorn Cap Nuts: Manufacturer & Exporter
An acorn nut closes off the end of a bolt. It covers the cut thread, keeps out dirt and water, and leaves a rounded, finished end that will not snag hands, clothing or cables.
Exotic Alloy manufactures and exports acorn nuts from Mumbai, India, for vehicle and trailer builders, marine and outdoor equipment makers, furniture and fit-out companies, and fastener distributors. We supply across India and export to Tunisia, North Africa, the Middle East and the Americas.
Inch acorn nuts
This page covers inch acorn nuts to SAE J483, which SAE writes for automotive and other ground vehicles and industrial equipment, where the nuts cover the ends of bolts, studs or screws. For metric domed cap nuts (DIN 1587, DIN 917) see hex cap nuts; for open nuts hex nuts.
- Standard
- SAE J483, high and low crown
- Sizes here
- #6–3/4 in (one-piece)
- Spanner
- 7/16 in at 1/4, 3/4 in at 1/2
- Full thread
- U ≈ 1 D
- Longest bolt
- Clamp + washers + U
- Materials
- Stainless 304 / 316, steel, brass
- Related
- Hex cap nuts, hex nuts, washers
Acorn Nut Specification
The range we manufacture and export.
SAE J483 One-Piece Low Crown Acorn Nut Dimensions
Inches.
| Size | UNC | Across flats F max / min | Across corners G max / min | Body ⌀ A | Overall height H | Hex height Q | Drill depth T | Full thread U |
|---|---|---|---|---|---|---|---|---|
| #6 | 32 | 0.3125 / 0.302 | 0.361 / 0.344 | 0.3 | 0.34 | 0.16 | 0.25 | 0.16 |
| #8 | 32 | 0.3125 / 0.302 | 0.361 / 0.344 | 0.3 | 0.34 | 0.16 | 0.25 | 0.16 |
| #10 | 24 | 0.375 / 0.362 | 0.433 / 0.413 | 0.36 | 0.41 | 0.19 | 0.28 | 0.19 |
| 1/4 | 20 | 0.4375 / 0.428 | 0.505 / 0.488 | 0.41 | 0.47 | 0.22 | 0.34 | 0.25 |
| 5/16 | 18 | 0.5 / 0.489 | 0.577 / 0.557 | 0.47 | 0.53 | 0.25 | 0.41 | 0.31 |
| 3/8 | 16 | 0.5625 / 0.551 | 0.65 / 0.628 | 0.53 | 0.62 | 0.28 | 0.45 | 0.38 |
| 1/2 | 13 | 0.75 / 0.736 | 0.866 / 0.84 | 0.72 | 0.81 | 0.38 | 0.59 | 0.5 |
| 5/8 | 11 | 0.9375 / 0.922 | 1.083 / 1.051 | 0.91 | 1 | 0.47 | 0.75 | 0.62 |
| 3/4 | 10 | 1.0625 / 1.045 | 1.227 / 1.191 | 1.03 | 1.16 | 0.53 | 0.88 | 0.75 |
F and G agree in globalfastener (SAE J483-2006), ITP Bolt, Duplex Fastener and Rimco; Q in globalfastener and ITP; A, H and T in ITP, Duplex and Rimco (Rimco lists T as a maximum); U in ITP and Duplex. F across flats, G across corners, A body diameter under the crown, H overall height, Q height of the hexagon, T depth of the drilled hole, U length of full thread. The full thread is about one diameter (0.98 to 1.16 D, our calculation).
Two-Piece Cap Nuts: Dimensions
A hex nut with a separate domed top. Inches.
| Size | Across flats F max / min | Across corners G max / min | Overall height H max / min | One-piece H for comparison |
|---|---|---|---|---|
| #4 | 0.248 / 0.225 | – | 0.2 / 0.177 | – |
| #5 | 0.3125 / 0.302 | 0.361 / 0.344 | 0.26 / 0.24 | – |
| #6 | 0.3125 / 0.302 | 0.361 / 0.344 | 0.26 / 0.24 | 0.34 |
| #8 | 0.3125 / 0.302 | 0.361 / 0.344 | 0.26 / 0.24 | 0.34 |
| #10 | 0.375 / 0.362 | 0.433 / 0.413 | 0.291 / 0.271 | 0.41 |
| 1/4 | 0.4375 / 0.423 | 0.505 / 0.482 | 0.338 / 0.318 | 0.47 |
| 5/16 | 0.562 / 0.545 | 0.65 / 0.621 | 0.385 / 0.365 | 0.53 |
| 3/8 | 0.625 / 0.607 | 0.722 / 0.692 | 0.432 / 0.412 | 0.62 |
| 5/8 | 0.938 / 0.909 | 1.083 / 1.037 | 0.807 / 0.787 | 1 |
Rows where ITP Bolt and Duplex Fastener agree. 1/2 and 3/4 in are left out: the two catalogues give different across-corners values there (1/2 in: 0.866 against 0.855). #4 has no across-corners value in either.
Choosing the Bolt Length for an Acorn Nut
- Longest bolt: clamped thickness + washers + U.
- U is about one diameter, so the bolt end should stand no more than about 1 D proud of the work.
- Allow for the bolt length tolerance and any washer under the nut.
- The finder below checks your bolt.
High Crown, Low Crown and Metric Acorn Nuts
Low crown
The SAE J483 type tabulated on this page: a short, rounded crown on the hexagon. Dimensions confirmed by four sources.
High crown
Also SAE J483, with the same width across flats and a taller dome. We could not confirm its full dimensions from two independent sources, so we make high crown nuts to your drawing or sample.
Metric
Domed cap nuts to DIN 1587 (M4–M24) and low cap nuts to DIN 917, with full tables, are on our hex cap nuts page.
Acorn Nut Finder: Dimensions & Bolt Length
Pick the nut and enter your joint; get the longest bolt, a check of your bolt and the order line.
Nut & joint
Dimensions from the tables on this page. Longest bolt = clamp + washers + full thread U (one-piece). Thread engaged = bolt length − clamp, up to U. Two-piece nuts: thread depth varies by maker, so we confirm it on order. Bolt lengths are under the head.
Result
Acorn Nut Materials & Finishes
| Material | Construction | Finish | Where |
|---|---|---|---|
| Stainless 304 / 304L | One- or two-piece | Polished or plain | Railings, furniture, food and general outdoor use; as in the photo |
| Stainless 316 | One-piece | Polished | Boats, docks, coastal and chemical areas |
| Steel | Usually two-piece | Zinc or chrome plated | Vehicles, trailers, machinery, indoor |
| Brass | One-piece | Plain or nickel plated | Decorative and electrical fittings |
ITP Bolt and Duplex Fastener describe steel low crown cap nuts as usually two-piece and stainless ones as 304L or equivalent, one- or two-piece. Match the nut to the bolt, stainless on stainless, so no galvanic pair forms.
How Our Acorn Nuts Are Made
Wire / bar
Stainless, steel or brass, certified by heat.
Form
Hexagon and crown cold formed, or machined from bar.
Drill & tap
Blind hole drilled to T, thread to U.
Polish
Dome and flats polished or tumbled.
Finish
Passivated, zinc, chrome or nickel plated.
Inspect
Thread and thread depth gauged.
Where Our Acorn Nuts Are Used
Vehicles
Trim, bumpers and exposed studs.
Trailers
Fenders, lights and fittings.
Marine
Deck hardware and railings in 316.
Furniture
Exposed fixings on frames.
Machinery
Guards and covers.
Playgrounds
Covered bolt ends on play equipment.
Acorn Nut Inspection & Certification
| Check | Method | Applied to |
|---|---|---|
| Thread | GO / NOT GO plug gauges | Every lot |
| Full thread U, drill depth T | Depth gauge | Every lot |
| F, G, H | Calipers | Every lot |
| Surface | Visual, polish standard | Every lot |
| Material | Heat certificate, PMI on request | Every heat |
| Coating | Thickness gauge | Plated lots |
Every shipment includes
- EN 10204 3.1 certificate
- Lot number on every box
- Packing list by size
On request
- EN 10204 3.2 with third-party inspection
- Salt spray tests on plated nuts
- Sets with bolts and washers