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ASME B18.6.9-2010 (2017) — Wing Nuts (Inch Series)
🪽 ASME B18.6.9-2010 (reaffirmed 2017) is the only current inch-series product standard for wing nuts in the U.S. national standards system. A wing nut is a nut having wings designed for manual turning without a driver or wrench, widely used where frequent assembly and disassembly are required without high preload — such as radiators, fixtures, instrument panels, covers, and adjusting devices. The Standard was developed through a complete rewrite initiated by B18 Subcommittee 6 in 2004 and completed in 2009, replacing the withdrawn ASME B18.17 (Wing Nuts, Thumb Screws, and Wing Screws).
💡 B18.6.9 covers nine types and styles of wing nuts in four Types (A, B, C, D). Classification is based first on the method of manufacture (cold forging, hot forging, die casting, stamping) and second on design characteristics (wing height, wing style, and base structure). The same thread size often has multiple options — choose by cost and duty.
1. Scope and General Framework 📌
The Standard classifies wing nuts into four types by manufacturing method and design features:
- Type A: cold forged or cold formed solid nuts with wings of moderate height. Some sizes are produced in regular, light, and heavy series to suit particular applications.
- Type B: hot forged solid nuts in two wing styles: Style 1 with moderate wing height and Style 2 with high wings.
- Type C: die cast solid nuts in three wing styles: Style 1 (moderate height; some sizes in regular and heavy series), Style 2 (low wings), and Style 3 (high wings).
- Type D: stamped sheet metal nuts in three styles: Style 1, Style 2 (low wings), and Style 3 (large base).
Thumb screws and wing screws, recognized as American National Standard, are included in ASME B18.6.8, not in this document. The inclusion of dimensional data does not imply that all products are stock production sizes — purchasers should consult suppliers on availability. There are no ISO standards comparable at this time.
⚠️ Wing nuts are “manual fasteners”; their wings are sized ergonomically for hand operation and must not be used as high-torque nuts driven with ordinary wrenches. Forcing extra load can snap the wings and create a safety hazard.
2. Type Classification and Size Series 🔧
| Type | Manufacturing Method | Styles | Wing Characteristics | Typical Applications |
|---|---|---|---|---|
| A | Cold forged/formed solid | — (regular/light/heavy series) | Moderate wing height | General quick clamps, fixtures, instruments |
| B | Hot forged solid | Style 1 / Style 2 | Moderate / high wings | Larger sizes, greater manual leverage |
| C | Die cast solid | Style 1 / 2 / 3 | Moderate / low / high wings | High-volume low-cost products, complex wing forms |
| D | Stamped sheet metal | Style 1 / 2 / 3 | Moderate / low wings / large base | Light-duty low-cost applications, large base spreads load |
All dimensions are in inch units. As a convention, when specifying normal sizes, decimal zeros in the fourth place shall be omitted (e.g., 0.25 rather than 0.2500). Internal threads conform to the applicable Unified thread requirements, with thread size and wing dimensions correlated in the dimension tables.
3. Engineering Practice Essentials 🛠️
- 🔍 Selection workflow: select nominal size by thread and load → choose manufacturing type by cost and batch volume (Type A/B for low volume, Type C/D for high-volume low-cost) → select wing height by operating torque (high wings for frequent heavy manual operation) → choose base structure by mounting surface (large base for thin panels or soft surfaces).
- 🛡️ Locking design: wing nut preload is limited and loosening under vibration is common; use spring washers, nylon insert lock nuts, or thread-locking adhesive where locking is required — never rely on excessive tightening torque.
- 📋 Surface treatment: zinc plating, anodizing, etc. improve appearance and corrosion resistance but may affect wing dimensions; follow the agreement between supplier and purchaser.
- 📊 Assembly inspection: stamped (Type D) wings and bases are bent-form structures; forced interference during installation can deform or crack the wings — avoid in assembly process design.
4. Frequently Asked Questions ❓
❓ Q: What is the relationship between B18.6.9 and the withdrawn B18.17?
A: B18.17 (Wing Nuts, Thumb Screws, and Wing Screws), published in 1968 and reaffirmed in 1983, was completely rewritten into B18.6.9 and withdrawn. B18.6.9 is now the only current inch-series standard for wing nuts, while thumb screws and wing screws moved to B18.6.8.
A: B18.17 (Wing Nuts, Thumb Screws, and Wing Screws), published in 1968 and reaffirmed in 1983, was completely rewritten into B18.6.9 and withdrawn. B18.6.9 is now the only current inch-series standard for wing nuts, while thumb screws and wing screws moved to B18.6.8.
❓ Q: Why do some sizes have regular, light, and heavy series?
A: Applications differ greatly in wing strength and hand torque requirements. Light series suit light frequent operation, while heavy series provide larger wing strength and better grip — choose by actual loading to avoid over-design or under-strength on the same thread size.
A: Applications differ greatly in wing strength and hand torque requirements. Light series suit light frequent operation, while heavy series provide larger wing strength and better grip — choose by actual loading to avoid over-design or under-strength on the same thread size.
❓ Q: Can wing nuts be tightened hard with pliers or a wrench?
A: Not recommended. Wing nuts are designed for hand operation, with wing size and thickness sized only for manual torque. Excessive wrench force can easily snap the wings, after which the nut is unusable.
A: Not recommended. Wing nuts are designed for hand operation, with wing size and thickness sized only for manual torque. Excessive wrench force can easily snap the wings, after which the nut is unusable.
🔍 Q: What does “omit decimal zeros in the fourth place” mean?
A: Inch dimensions are often written as four-decimal values (e.g., 0.2500 in). The Standard’s convention is to omit the fourth-place zero when specifying normal sizes (write 0.25), reducing writing errors — a notation practice that does not change the physical size.
A: Inch dimensions are often written as four-decimal values (e.g., 0.2500 in). The Standard’s convention is to omit the fourth-place zero when specifying normal sizes (write 0.25), reducing writing errors — a notation practice that does not change the physical size.
