AN bolts (short for Army-Navy bolts) are the industry standard in aviation and high-performance motorsports. Known for their strength, precision, and interchangeability, they’re used in everything from aircraft wings to race car suspension systems. But knowing how to accurately measure AN bolts—and choose the right nuts and washers—is critical to safety and performance.
What Are AN Bolts?
AN bolts are manufactured to MIL-SPEC standards, ensuring tight tolerances and dependable strength. They’re typically made of cadmium-plated steel or corrosion-resistant stainless steel. Each bolt is labeled with a part number like AN3-12A, which tells you everything about its size and configuration. For example, AN3 bolts, AN4 bolts, and AN6 bolts are among our most popular options.
How to Measure AN Bolts
- Diameter
- This is the grip size (not the head) and is represented by the number after “AN”.
- Each number equals 1/16 inch.
AN Number Diameter AN3 3/16″ AN4 1/4″ AN5 5/16″ AN6 3/8″ - Length
- Measured from under the head to the end of the threads (grip + thread).
- The second number in the part (e.g., the “12” in AN3-12A) equals 1/8 inch per unit.
Example: AN3-12A = 3/16″ diameter, 1.5″ total length. For a great starter set, see our AN3 and AN4 Bolt Kit.
- Grip Length (Unthreaded Shank)
- Critical for shear applications.
- Available in charts or use grip gauges: see Vinyl Bolt Gauge or Aluminum Bolt Gauge.
Common AN Bolt Suffixes
| Suffix | Meaning |
|---|---|
| A | No hole in the shank |
| H | Drilled head for safety wire |
| (none) | Standard drilled shank for cotter pin |
Matching AN Nuts
Find all AN nuts here. If you want them sorted for you, try our nut kit.
| Nut Type | Use Case |
|---|---|
| AN365 | Nylon lock nut – most common for general use |
| AN310 | Castle nut – used with cotter pin for critical joints |
| AN316 | Check nut – used with rod ends or jam nuts |
| AN320 | Shear castle nut – lighter, used in shear load only |
Washers for AN Bolts
Browse our full washer selection AN970 Flat Washer, AN960 Flat Washer, and AN960L Thin Washer.
| Washer Type | Use Case |
|---|---|
| AN960 | Standard flat washer |
| AN960L | Thinner version of standard washer |
| AN970 | Large flat area washer – for wood or composites |
Pro Tip: Always use two washers if the nut or bolt head might rotate on the surface.
Tools You’ll Need
- Grip gauge / Vinyl Bolt Gauge or Aluminum Bolt Gauge
- Caliper or ruler for measuring length
- Safety wire pliers if using drilled heads
Wicks Makes It Easy
We carry:
- Full inventory of AN bolts, nuts, and washers.
- Bolt measuring tools
- Hardware kits for builders, restorers, and student teams
Contact Us:
Email: info@wicksaircraft.com
Phone: 1-800-221-9425