Hex Locknut 1/2"-13 Zinc Plated Grade 5 290-002598

Hex Locknut 1/2"-13 Zinc Plated Grade 5 290-002598

1/2"-13 Trailer Locknut

The Hex Locknut 1/2"-13 Zinc Plated Grade 5 290-002598 is a replacement trailer hardware fastener used on compatible EZ Loader boat trailers. This locknut is designed for 1/2"-13 coarse-thread bolts, U-bolts, and related trailer hardware where a locking-style nut is required.

This nut is commonly used in trailer suspension, bracket, bunk, roller, frame, and running gear hardware applications depending on the trailer model and setup. Correct thread size matters because 1/2"-13 coarse thread hardware is not interchangeable with 1/2"-20 fine thread hardware.

The zinc-plated finish helps provide corrosion resistance for marine trailer use. Because boat trailers are exposed to road spray, freshwater, saltwater, ramp use, and vibration, replacing worn, corroded, rounded, or questionable fasteners is important during service.

1/2"-13 Hex Locknut Features

• Replacement 1/2"-13 coarse-thread hex locknut for compatible trailer hardware
• Nyloc-style locking design helps resist loosening from vibration and road shock
• Grade 5 zinc-plated steel construction
• Commonly used with compatible 1/2" trailer bolts and U-bolts
• Useful for replacing rusted, rounded, worn, or missing trailer nuts
• Designed for boat trailer hardware service and repair applications

Typical EZ Loader Trailer Applications

This locknut may be used on compatible EZ Loader trailer hardware where a 1/2"-13 coarse-thread nut is required. Common use areas may include suspension hardware, U-bolt hardware, bunk or bracket hardware, roller hardware, frame-mounted hardware, and other trailer service points 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 Nyloc-Style Locknuts

EZ Loader commonly uses nylon-insert locknuts in trailer hardware locations where vibration, road shock, and repeated loading can loosen standard nuts. The nylon insert 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 nyloc-style locknut helps reduce that risk by keeping steady thread pressure on the bolt.

For best results, replace worn or repeatedly removed locknuts during service, especially on suspension, bunk, bracket, roller, and frame hardware.

Important Difference: 1/2"-13 vs. 1/2"-20

This part is a 1/2"-13 coarse-thread locknut. It is not the same as a 1/2"-20 fine-thread wheel fastener nut.

Many trailer wheel studs and lug bolts use fine-thread hardware, while many trailer brackets, U-bolts, and frame hardware locations use coarse-thread hardware. If the thread pitch does not match, the nut can cross-thread, strip, or fail to tighten correctly.

Installation Considerations

• Confirm the mating bolt or U-bolt is 1/2"-13 coarse thread.
• Do not force the nut onto fine-thread hardware.
• Inspect the bolt, U-bolt, bracket, and mounting surface before reassembly.
• Replace badly rusted, stretched, rounded, or damaged hardware before towing.
• Replace locknuts 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.

Hex Locknut Fitment Guidance

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

• Confirm the thread size is 1/2"-13.
• Confirm the hardware application uses a 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 locknut may not clamp properly, and a mismatched thread pitch can damage the bolt or U-bolt. When servicing suspension, bunk, bracket, roller, or frame hardware, replacing questionable locknuts is often cheaper than fighting seized, loose, 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 or U-bolt thread size
• Hardware location on the trailer
• Photos of the existing nut, bolt, bracket, or U-bolt