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1/2-20 King Pin Slotted Jam Nut (Castle Nut)
50FNSJ5 ½-20 Slotted Jam Nut (Castle Nut)
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1/2-20 King Pin Slotted Jam Nut (Castle Nut)

Part Number: 50FNSJ5
Online Price: $2.99
50FNSJ5 – 1/2"-20 Castle Nut (Slotted Jam Nut) for Kingpins & Safety Retention
Availability: In Stock.

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Description

50FNSJ5 – 1/2"-20 Slotted Castle Nut (Jam Nut) – Right-Hand Thread


The 50FNSJ5 1/2"-20 Slotted Jam Nut, also known as a castle nut, is a critical safety fastener designed for high-vibration and performance environments where components must remain securely locked in place. Its slotted design allows for the use of cotter pins, R-clips, or safety wire to prevent loosening—especially on rotating or load-bearing parts like spindles and kingpins.


Commonly used on racing go-karts, lawnmowers, and custom chassis, this castle nut is ideal for securing kingpin bolts, steering arms, wheel hubs, and other areas where safety retention is required to meet racing tech regulations. Made from durable steel with 1/2"-20 right-hand threads, this nut comes unplated, allowing for custom surface treatment as needed.


Product Specifications:

  • Thread Size: 1/2"-20 UNF
  • Thread Direction: Right-hand
  • Style: Castle (slotted) jam nut
  • Finish: Bare steel (no plating)
  • Application: Kingpins, steering components, and wheel assemblies
  • Locking Method: Use with cotter pin, R-clip, or safety wire
  • Sold Individually


Key Features:

  • Ideal for safety-critical components on racing vehicles
  • Commonly used to secure spindle kingpins in go-karts and race mowers
  • Prevents loosening from vibration and rotation
  • Compatible with standard 1/2"-20 threaded shafts
  • Bare steel for custom plating or anti-corrosion treatment
  • Complies with most racing safety tech inspection standards


Recommended For:

  • Racing go-karts and mini bikes
  • Racing lawnmowers (USLMRA, ARMA, Outlaw classes)
  • Custom-built small engine vehicles
  • Any application needing safety-locked fasteners

FAQ

What is the 50FNSJ5 castle nut used for?

A: It’s commonly used to secure kingpin bolts, wheel hubs, and steering arms on racing lawnmowers, go-karts, and similar small-engine vehicles. The slotted design allows you to lock the nut with a cotter pin, R-clip, or safety wire to prevent it from loosening.


What is the thread size and direction?

A: The 50FNSJ5 castle nut features 1/2"-20 UNF right-hand threads, which are standard for many spindle and chassis fasteners in racing applications.


Does it come plated for corrosion resistance?

A: No, this nut comes in bare steel, giving you the option to apply your own plating or anti-corrosion coating depending on your application.


Do I need to use a cotter pin with it?

A: Yes, for proper safety retention, a cotter pin, safety wire, or similar retention method is strongly recommended. These are not included with the nut.


Is this nut legal for tech inspection in racing?

A: Yes, castle nuts like the 50FNSJ5 are often required by tech inspectors in racing series such as USLMRA, ARMA, and other competitive karting or lawnmower classes.

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