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ASME B18.1.2-1972 (2016) — Large Rivets (1/2 Inch Nominal Diameter and Larger)
🔩 ASME B18.1.2-1972 (2016) (originally ANSI B18.1.2-1972, a revision of B18.4-1960) is the dedicated American National Standard for large solid rivets, covering nominal shank diameters of 1/2 inch and larger. It provides complete general and dimensional data for six standardized head types, together with dimensional data for manufactured heads after driving, driven heads, hold-on (dolly bar) impressions, and rivet set impressions. The Standard serves as the unified manufacturing and acceptance reference for hot and cold riveting in bridges, boilers, shipbuilding, and heavy machinery.
💡 The “acceptance-first” principle is explicit: whenever the acceptability of a product is in question, the dimensions in the tables govern — never a recalculation by the appendix formulas, which exist only to explain how the dimensional data are derived.
1. Scope and General Framework 📌
B18.1.2 provides complete general and dimensional data for the recognized “American National Standard” types of large solid rivets, with appendices containing the formulas on which the dimensional data are based. The Standard expressly notes that listing in the dimensional tables does not imply that every product described is a stock production size — consumers should consult manufacturers about availability. When nonstandard diameters or head proportions are needed for special applications, head proportions should preferably follow the formulations in the appendices.
Six head types are standardized: button head, high button head (acorn), cone head, flat countersunk head, oval countersunk head, and pan head. All other head types for large solid rivets are considered special and require mutual agreement.
⚠️ Large rivets are normally furnished with straight shanks up to the head. When specified, the swell neck (Table 7 of the Standard) applies to all standard large rivets except the flat countersunk and oval countersunk heads — confirm that the manufacturing and driving process can accommodate the swell neck before specifying it.
2. Technical Requirements and Dimensions 📏
Separate tables give, for each head type, the maximum and minimum limits for shank diameter, head diameter, and head height. The symbol system stays consistent with the small solid rivet standard (ASME B18.1.1). Standard shank diameters and head proportions are those given in the tables; any other values are considered special.
| Standard Head Type | Head Features | Typical Applications | Table |
|---|---|---|---|
| Button head | Hemispherical dome; simple to form | Boilers, pressure vessels, general steelwork | 1 |
| High button head (acorn) | Taller, fuller dome | Heavy connections needing more upset stock | 2 |
| Cone head | Conical top with pronounced transition | Bridges and heavy truss structures | 3 |
| Flat countersunk head | Conical bearing surface, head flush | Joints requiring a smooth external surface | 4 |
| Oval countersunk head | Countersunk cone with oval crown | Where a rounded, low-profile head is desired | 5 |
| Pan head | Flat top, cylindrical sides | Marine and general machinery assembly | 6 |
Beyond manufactured-shape dimensions, Tables 8 through 11 give dimensions for manufactured heads after driving and driven heads of four head types, as well as hold-on (dolly bar) and rivet set impressions. These impression dimensions dictate the cavity shape of the riveting tooling and are critical for producing a properly formed driven head.
| Dimension Element | Symbol | Description |
|---|---|---|
| Head diameter | A | Max/min manufactured head diameter by head type |
| Head height | H | Height range measured from the bearing surface |
| Shank diameter | D | Standard shank diameter, straight to the head |
| Countersink angle | — | Included angle and depth for countersunk heads |
| Driven head size | — | Driven-head diameter/height limits (Tables 8–11) |
⚠️ In any dimensional dispute over acceptance, the Standard’s tables prevail; results recalculated from the appendix formulas must not be used as the basis for judging conformance. Reference the exact table numbers and edition year in purchase orders.
3. Engineering Practice Essentials 🛠️
- 🔍 Selection workflow: size the rivet diameter from structural strength → choose the head type by surface and process needs → read head and driven-head dimensions from the tables → select tooling (dolly bar and rivet set) → define hot or cold driving and any heating rules.
- 🔧 Hot vs. cold driving: large rivets were historically hot-driven — the heated shank is upset to fill the hole and shrinks on cooling to create clamping force. Today high-strength bolting dominates new steel construction; riveting persists in repair, bridge maintenance, and specialized heavy assemblies.
- 📐 Tooling impression control: the dolly bar and rivet set cavities should be formed to the impression dimensions of Tables 8–11; too deep or too shallow a cavity produces an undersized or damaged driven head.
- 📋 Acceptance control: enforce the “tables govern” rule for inspectors; after driving, check driven-head diameter, height, and surface defects (cracks, indentations) against the tabulated limits.
4. Frequently Asked Questions ❓
❓ Q: What is the difference between B18.1.2 and B18.1.1?
A: Both belong to the B18 rivet family. B18.1.1 covers small solid rivets; B18.1.2 covers large solid rivets of 1/2 inch nominal diameter and larger, with its own head types and dimension tables. Select the standard by nominal diameter.
A: Both belong to the B18 rivet family. B18.1.1 covers small solid rivets; B18.1.2 covers large solid rivets of 1/2 inch nominal diameter and larger, with its own head types and dimension tables. Select the standard by nominal diameter.
❓ Q: Why must acceptance be based on the tables rather than the appendix formulas?
A: This is an express provision of the Standard (Section 1). The formulas explain how the dimensional data are derived, but the tables are the consensus values coordinated by the committee; recalculations can introduce rounding and historical differences, so the tables are authoritative for acceptance.
A: This is an express provision of the Standard (Section 1). The formulas explain how the dimensional data are derived, but the tables are the consensus values coordinated by the committee; recalculations can introduce rounding and historical differences, so the tables are authoritative for acceptance.
🔍 Q: When should a swell-neck rivet be specified?
A: When the joint needs a larger cross-section at the neck or a smoother transition into the hole. Per Table 7, the swell neck applies to all standard large rivets except flat and oval countersunk heads, and it must be stated separately on the order.
A: When the joint needs a larger cross-section at the neck or a smoother transition into the hole. Per Table 7, the swell neck applies to all standard large rivets except flat and oval countersunk heads, and it must be stated separately on the order.
❓ Q: Does listing in the tables mean every size is stocked?
A: No. The Standard states that inclusion in the dimensional tables does not imply stock production status; nonstandard diameters and head proportions are special products, so confirm availability and lead time with the manufacturer before ordering.
A: No. The Standard states that inclusion in the dimensional tables does not imply stock production status; nonstandard diameters and head proportions are special products, so confirm availability and lead time with the manufacturer before ordering.
