Crownlock Nut 5/8"-11 Zinc Plated Grade 5 290-002596

Crownlock Nut 5/8"-11 Zinc Plated Grade 5 290-002596

5/8" All-Metal Locknut

The Crownlock Nut 5/8"-11 Zinc Plated Grade 5 290-002596 is a replacement all-metal locking nut used on compatible EZ Loader boat trailer hardware. This crownlock nut is designed for 5/8"-11 coarse-thread bolts where a strong vibration-resistant fastener is required.

A crownlock nut is an all-metal prevailing-torque locknut. Instead of using a nylon insert, the top of the nut is slightly distorted or crimped so it grips the bolt threads as it tightens. This helps resist loosening from road vibration, shock loading, trailer flex, and repeated launch-and-retrieval use.

This nut is commonly used in trailer hardware locations such as pivot bolts, roller assemblies, brackets, suspension hardware, and other high-stress fastening points depending on the trailer model and setup. Correct thread size matters because 5/8"-11 coarse thread hardware is not interchangeable with fine-thread 5/8" hardware.

5/8"-11 Crownlock Nut Features

• Replacement 5/8"-11 coarse-thread crownlock nut for compatible EZ Loader trailer hardware
• All-metal locking design helps resist loosening from vibration and shock
• Grade 5 zinc-plated steel construction
• Commonly used with compatible 5/8" trailer bolts and pivot hardware
• Useful for replacing rusted, rounded, worn, or missing trailer nuts
• Designed for boat trailer hardware service and repair applications

What Is a Crownlock Nut?

A crownlock nut is an all-metal locknut. The top of the nut is slightly crimped or distorted so it grips the bolt threads as it tightens. That extra thread pressure helps the nut resist backing off under vibration, shock, and repeated trailer movement.

Unlike a nyloc nut, a crownlock nut does not use a nylon insert. That makes it useful in heavier trailer hardware locations where an all-metal locking fastener is preferred.

Typical EZ Loader Trailer Applications

This crownlock nut may be used on compatible EZ Loader trailer hardware where a 5/8"-11 coarse-thread all-metal locknut is required. Common use areas may include pivot bolts, roller assemblies, bracket hardware, suspension hardware, and heavy trailer hardware locations depending on the trailer model.

Because EZ Loader trailers use different fasteners by application, always compare the old nut, bolt, thread pitch, and hardware location before ordering.

Why EZ Loader Uses Crownlock-Style Nuts

EZ Loader uses crownlock-style nuts in trailer hardware locations where vibration, road shock, and repeated loading can loosen standard nuts. The crimped all-metal locking section grips the bolt threads and helps maintain clamping pressure without relying on a separate lock washer.

This matters on boat trailers because lock washers can flatten, crack, or break under stress. When that happens, a gap can form and hardware may loosen over time. A crownlock nut helps reduce that risk by keeping steady thread pressure on the bolt.

For best results, replace worn or repeatedly removed crownlock nuts during service, especially on pivot bolts, suspension, roller, bracket, and frame hardware.

Important Difference: 5/8"-11 vs. 5/8"-18

This part is a 5/8"-11 coarse-thread crownlock nut. It is not the same as a 5/8"-18 fine-thread nut.

Trailer hardware may use either coarse-thread or fine-thread fasteners depending on the application. If the thread pitch does not match, the nut can cross-thread, strip, or fail to tighten correctly.

Associated / Compatible Parts

This crownlock nut is commonly used with compatible 5/8" trailer hardware. Confirm your specific bolt and application before ordering.

Installation Considerations

• Confirm the mating bolt is 5/8"-11 coarse thread.
• Do not force the nut onto fine-thread hardware.
• Inspect the bolt, bracket, roller assembly, pivot point, and mounting surface before reassembly.
• Replace badly rusted, stretched, rounded, or damaged hardware before towing.
• Replace crownlock nuts that have been repeatedly removed and reinstalled, especially in high-vibration trailer locations.
• Use the proper wrench or socket to avoid rounding the nut.
• Tighten hardware to the proper specification for the trailer application.

Crownlock Nut Fitment Guidance

This is not a universal nut for every trailer hardware location.

• Confirm the thread size is 5/8"-11.
• Confirm the hardware application uses a crownlock or all-metal locknut.
• Confirm the grade and finish are suitable for the repair location.
• Compare the old nut and bolt before ordering.

Real-World Insight

Small trailer hardware often causes bigger problems when it is reused past its service life. A corroded or rounded crownlock nut may not clamp properly, and a mismatched thread pitch can damage the bolt. When servicing roller assemblies, pivot points, brackets, suspension, or frame hardware, replacing questionable locknuts is often cheaper than fighting loose, seized, or damaged hardware later.

Questions or Need Help Matching Parts?

We’re based in Hardeeville, South Carolina, serving customers nationwide.

📞 Call us — we answer the phone and help you get it right.
📧 Send photos if needed — often the fastest way to confirm fitment.

We focus on matching parts correctly the first time.

What to Have Ready When You Call

• Trailer year, make, and model
• VIN, if available
• Old bolt thread size
• Hardware location on the trailer
• Photos of the existing nut, bolt, bracket, roller assembly, or pivot point