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Find the exact nut size, socket size, and wrench size for your bolt diameter. Get specifications for UNC, UNF, and metric standards instantly.
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Standard six-sided nut. Most common type for general fastening. Full height provides maximum thread engagement.
Thinner hex nut, approximately 60% of standard height. Used to lock another nut in place.
Deformed or self-locking nut that resists vibration loosening. Built-in locking feature provides vibration resistance.
Hex nut with integrated washer flange. Larger bearing surface distributes load across surface.
Quick reference for socket sizes needed for common bolt diameters:
| Bolt Diameter (Inches) | Thread Pitch | Nut Width (AF) | Socket Size |
|---|---|---|---|
| 1/4" | UNC | 7/16" | 3/8" |
| 5/16" | UNC | 1/2" | 7/16" |
| 3/8" | UNC | 9/16" | 1/2" |
| 1/2" | UNC | 3/4" | 5/8" |
| 5/8" | UNC | 15/16" | 3/4" |
| 3/4" | UNC | 1 1/8" | 7/8" |
| 7/8" | UNC | 1 5/16" | 1" |
| 1" | UNC | 1 1/2" | 1 1/8" |
Unified National Coarse thread. Most common thread standard for general purpose fastening in North America.
Unified National Fine thread. Used where stronger grip and better vibration resistance is needed.
International Organization for Standardization. Standard for metric fasteners worldwide.
Key standards for nut sizing and specifications:
AF stands for "Across Flats" - it's the distance between two opposite flat sides of a hex nut. This determines the wrench size you need to tighten or loosen the nut.
A wrench size (AF) is the flat-to-flat measurement of the nut used with a wrench or spanner. A socket size is the hole size needed for a socket wrench. Sockets are typically 1/8" smaller than the AF measurement.
Jam nuts are thinner to reduce overall assembly height while still providing locking capability. Two jam nuts together create a stronger lock than a single regular nut.
No, metric and imperial threads are not compatible. A 5/16" bolt requires a UNC or UNF nut, not a metric nut. However, the wrench sizes may sometimes appear similar but will not fit properly.
UNC = Unified National Coarse (wider spacing between threads, faster to install). UNF = Unified National Fine (more threads per inch, stronger grip, vibration resistant).
Use the AF (Across Flats) measurement and subtract approximately 1/8" for inch-based nuts. For metric, refer to your socket set size. Always verify with a test socket before purchasing a full set.
TPI means "Threads Per Inch" - it's the number of thread crests in one inch of bolt length. Higher TPI means finer threads (UNF), lower TPI means coarser threads (UNC).
Use flange nuts when fastening to soft materials (wood, plastic) or where you need to distribute load over a larger area. The integrated washer prevents surface damage and reduces the need for separate washers.
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