Set screws may be small, but they play an outsized role in securing components across industrial, mechanical, and aerospace applications. Their performance—and the reliability of the system they support—depends heavily on the type of locking mechanism selected. The right locking feature prevents loosening, reduces maintenance, improves safety, and ensures long-term stability under load and vibration.

Below is a comprehensive, professional overview of the most common locking mechanisms for set screws, including the increasingly popular plastic strip locking mechanism, and how to determine the best option for your application.

1) Standard (Non-Locking) Set Screws

Standard set screws rely solely on thread friction and the geometry of the point type (cup, cone, flat, etc.) to hold position.

Advantages

• Cost-effective
• Widely available
• Suitable for static assemblies with minimal vibration

Limitations

• Most prone to loosening under vibration
• May require an additional locking method for dynamic equipment

2) Nylon Patch (Pre-Applied Coating)

A nylon or polymer patch creates prevailing torque by adding friction to the screw’s threads.

Advantages

• Excellent vibration resistance
• Clean, pre-applied solution—no additional hardware
• Suitable for high-volume production
• Partially reusable

Common Uses

• Industrial machinery
• Electronics
• Assemblies with moderate vibration

Considerations

• Increased installation torque
• Not ideal for high-temperature environments

3) Nylon Pellet (Radially Inserted Locking Element)

A nylon pellet is inserted into a drilled hole in the screw, providing consistent resistance throughout the tightening and adjustment process.

Advantages

• Highly repeatable and adjustable
• Does not damage mating threads
• Provides reliable prevailing torque

Common Uses

• Precision assemblies
• Valves and instrumentation
• Adjustable mechanisms

Considerations

• Higher cost than standard or patch screws
• Lower surface coverage than a full patch, but more consistent for repeated adjustments

4) Strip Locking Mechanism (Plastic Locking Strip)

The strip locking mechanism incorporates a plastic strip—typically made from engineered polymers—inserted longitudinally along the screw threads. As the set screw is installed, the strip compresses and creates continuous friction between the screw and mating threads.

Advantages

• Provides strong, consistent prevailing torque without adhesives
• Fully polymer-based, offering smooth adjustment without damaging mating threads
• More thermally stable than nylon patches in moderate heat ranges
• Highly reusable—strip returns to form after tightening
• Excellent for assemblies requiring frequent adjustments

Common Uses

• Aerospace and defense hardware
• Instrumentation and metering systems
• High-vibration environments
• Applications where nylon pellets do not provide enough surface engagement

Considerations

• Higher cost compared to standard locking features
• Requires precise installation during manufacturing
• Temperature limitations depend on polymer grade

5) Mechanical Locking Through Geometry (Cup, Cone, Knurled, Serrated)

These locking mechanisms rely on the point shape to physically engage the mating surface.

Point Types

• Cup Point: Balanced holding strength; most common
• Cone Point: Maximum penetration for secure engagement
• Knurled or Serrated Cup: Increased bite for vibration resistance

Advantages

• Strong mechanical holding force
• Ideal for torque transfer applications

Common Uses

• Collars, pulleys, gears
• Power transmission components

Considerations

• Can damage softer shafts
• Not ideal when frequent adjustments are needed

6) Chemical Threadlockers (Liquid Adhesives)

Liquid anaerobic adhesives cure between the threads, creating a chemical bond.

Advantages

• Strong resistance to vibration
• Seals threads against corrosion
• Available in low-, medium-, and high-strength formulas

Common Uses

• Field repairs
• Applications where pre-applied locking features are unavailable

Considerations

• Adds steps to the assembly process
• Requires curing time
• Less repeatable than pre-applied locking features

Choosing the Right Locking Mechanism

Consider Vibration Level

• High vibration: nylon patch, plastic strip, nylon pellet
• Low vibration: standard set screws may suffice

Adjustment Frequency

• Frequent adjustments: pellet or plastic strip
• Permanent setting: threadlocker or cone point

Material Compatibility

• Soft shafts: avoid aggressive mechanical points

Environmental Factors

• Temperature, chemical exposure, and installation torque all influence selection

Conclusion

Set screws may be fundamental components, but choosing the right locking mechanism is essential for ensuring performance, preventing loosening, and protecting critical assemblies. From nylon patches to plastic strip locking systems, each option serves a specific purpose—and selecting correctly can dramatically improve reliability and reduce long-term maintenance.