Low Crown Acorn Nuts (Inch Series)
Low crown acorn nuts, inch series 0.138–1.25 nominal — the dome-top hex nut with a shortened crown for clearance-limited assemblies, with the collected per-size table: width across flats and corners, body diameter, overall and hexagon heights, drill depth and full-thread length.
Last updated: 2026-11
Specifications
An acorn nut is a hex nut with a dome: the crown closes over the thread run-out so no exposed thread, snag point or dirt trap is left above the nut. The low crown pattern shortens that dome — the tabulated data carries overall height H beside hexagon height Q, and the difference between them (0.34 versus 0.16 at the 0.138 sizes, 1.95 versus 0.91 at 1.25) is the crown itself, roughly halved compared with the high crown pattern. That makes the low crown the choice where the nut must fit under a cover, inside a channel, or against a sliding part that a full dome would foul. The tabulated ladder runs 0.138 through 1.25 nominal and carries per size: width across flats F (max/min — 0.3125/0.302 at the small sizes up to 1.8125/1.788 at 1.25), across corners G (max/min), body diameter A, overall height H, hexagon height Q, nose radius R, body radius S, maximum drill depth T (the tap-drill depth the dome allows before the drill breaks through the crown — the practical limit on effective thread inside an acorn nut) and minimum full thread U. Read T and U together when specifying: at 0.138, only 0.16 in of full thread is guaranteed, so an acorn nut is a light-duty or finish-facing fastener, not a high-clamp one. Only low crown rows are tabulated, and sizes below 0.138 nominal are not established in the tabulated data (see the table footnote); the high crown pattern is covered on its own page with its own two-piece table. Threads, property classes and finishes are not tabulated — per RFQ.
| Pattern | Low crown acorn (dome-top) hex nut, inch series — dome closes the thread run-out; low crown trades dome height for clearance (published tables cover the low crown pattern only) |
|---|---|
| Size range | Nominal 0.138 – 1.25 in, sixteen sizes; sizes below 0.138 nominal are not covered by published tables |
| Tabulated geometry | Per size: width across flats F (max/min), across corners G (max/min), body dia. A, overall height H, hexagon height Q, nose radius R, body radius S, max drill depth T, min full thread U — e.g. 0.500 nominal: F 0.750–0.736, H 0.81, Q 0.38, T 0.59, U 0.50 |
| Crown proportions | H − Q is the dome: 0.18 at 0.138 nominal growing to 1.04 at 1.25 — the low-crown envelope that decides cover and channel clearance |
| Threads / classes / finishes | Not tabulated by the collected specification — per RFQ (state thread series and finish at quotation) |
| Product | Nominal Dia. (d) | Width Across Flats (F) Max | F Min | Width Across Corners (G) Max | G Min | Body Dia. (A) | Overall Height (H) | Hexagon Height (Q) | Nose Radius (R) | Body Radius (S) | Max Drill Depth (T) Max | Min Full Thread (U) Min |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Low crown acorn nut | 0.1380 | 0.3125 | 0.302 | 0.361 | 0.344 | 0.30 | 0.34 | 0.16 | 0.08 | 0.17 | 0.25 | 0.16 |
| Low crown acorn nut | 0.1640 | 0.3125 | 0.302 | 0.361 | 0.344 | 0.30 | 0.34 | 0.16 | 0.08 | 0.17 | 0.25 | 0.16 |
| Low crown acorn nut | 0.1900 | 0.3750 | 0.362 | 0.433 | 0.413 | 0.36 | 0.41 | 0.19 | 0.09 | 0.22 | 0.28 | 0.19 |
| Low crown acorn nut | 0.2160 | 0.3750 | 0.362 | 0.433 | 0.413 | 0.36 | 0.41 | 0.19 | 0.09 | 0.22 | 0.31 | 0.22 |
| Low crown acorn nut | 0.2500 | 0.4375 | 0.428 | 0.505 | 0.488 | 0.41 | 0.47 | 0.22 | 0.11 | 0.25 | 0.34 | 0.25 |
| Low crown acorn nut | 0.3125 | 0.5000 | 0.489 | 0.577 | 0.557 | 0.47 | 0.53 | 0.25 | 0.12 | 0.28 | 0.41 | 0.31 |
| Low crown acorn nut | 0.3750 | 0.5625 | 0.551 | 0.650 | 0.628 | 0.53 | 0.62 | 0.28 | 0.14 | 0.33 | 0.45 | 0.38 |
| Low crown acorn nut | 0.4375 | 0.6250 | 0.612 | 0.722 | 0.698 | 0.59 | 0.69 | 0.31 | 0.16 | 0.36 | 0.52 | 0.44 |
| Low crown acorn nut | 0.5000 | 0.7500 | 0.736 | 0.866 | 0.840 | 0.72 | 0.81 | 0.38 | 0.19 | 0.42 | 0.59 | 0.50 |
| Low crown acorn nut | 0.5625 | 0.8750 | 0.861 | 1.010 | 0.982 | 0.84 | 0.94 | 0.44 | 0.22 | 0.50 | 0.69 | 0.56 |
| Low crown acorn nut | 0.6250 | 0.9375 | 0.922 | 1.083 | 1.051 | 0.91 | 1.00 | 0.47 | 0.23 | 0.53 | 0.75 | 0.62 |
| Low crown acorn nut | 0.7500 | 1.0625 | 1.045 | 1.227 | 1.191 | 1.03 | 1.16 | 0.53 | 0.27 | 0.59 | 0.88 | 0.75 |
| Low crown acorn nut | 0.8750 | 1.2500 | 1.231 | 1.443 | 1.403 | 1.22 | 1.36 | 0.62 | 0.31 | 0.70 | 1.00 | 0.88 |
| Low crown acorn nut | 1.0000 | 1.4375 | 1.417 | 1.660 | 1.615 | 1.41 | 1.55 | 0.72 | 0.36 | 0.81 | 1.12 | 1.00 |
| Low crown acorn nut | 1.1250 | 1.6250 | 1.602 | 1.876 | 1.826 | 1.59 | 1.75 | 0.81 | 0.41 | 0.92 | 1.31 | 1.12 |
| Low crown acorn nut | 1.2500 | 1.8125 | 1.788 | 2.093 | 2.038 | 1.78 | 1.95 | 0.91 | 0.45 | 1.03 | 1.44 | 1.25 |
- Row 1 (Low crown acorn nut): The ladder begins at d = 0.1380; smaller nominal sizes below 0.1380 are not present in the tabulated data, and high-crown rows are not tabulated (low-crown rows only). Confirm coverage before quoting below 0.1380 or for high crown.
- Row 2 (Low crown acorn nut): The 0.1380 and 0.1640 rows share identical F/G/A/H/Q/R/S/T/U values in the source — reproduced verbatim.
Materials
- Material and finish specified per RFQ — acorn nuts are often chosen for appearance as well as function; state the exposed-surface finish requirement with the order
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 (Low Crown Acorn Nuts (Inch Series)) 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 is a low crown acorn nut the right choice over the standard dome pattern?
Measure the clearance you actually have, then read H and Q off the collected table. The low crown exists for assemblies where the full dome fouls something: a nut inside a sliding cover, under a hinged lid, against a cable run, or in a channel whose wall sits at the high-crown radius. The numbers to compare are overall height H (the full envelope the dome occupies) and hexagon height Q (the wrenchable hex section) — at 0.500 nominal the low crown stands 0.81 in overall with a 0.38 hex, so the dome adds only 0.43 in beyond what a plain hex nut of the same wrench size would need. If your clearance is larger than that, the choice is aesthetic or functional rather than spatial: an acorn nut protects the thread end from corrosion and handling damage and removes the exposed thread that snaggs webbing, gloves or fabric. Two practical limits from the same table: maximum drill depth T is the depth the crown permits before breakthrough, and minimum full thread U is what is actually guaranteed — at the small sizes (0.16 in at 0.138 nominal) that is short, so do not ask an acorn nut to carry a clamp load a full-height nut would take. The collected sweep covers the low crown pattern from 0.138 nominal; the high crown pattern carries its own collected table on the high crown page, while low-crown sizes below 0.138 should be quoted explicitly and confirmed at RFQ.
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