Locking and Prevailing Torque Guide

A nylon insert, patch, or pellet is factory-applied to a portion of the thread. During assembly the nylon deforms under compression and creates a mechanical interference fit on the thread directly opposite the patch. This asymmetric friction resists loosening without any chemical bonding. The locking zone is localized to approximately 120 degrees of arc.

• Purely mechanical locking via deformed nylon squeezing opposing thread flanks
• Friction acts on the thread opposite the patch location, not beneath it
• Prevailing torque is measurable from the very first installation turn
• No cure time required; locks immediately at assembly
• Suitable for reuse across multiple removal and reinstallation cycles
• Temperature rated typically up to 250 deg F (verify product spec)
• Prevailing-Off torque decreases progressively with each removal cycle
• Not suitable where chemical resistance to nylon solvents is critical

IFI-524 (Metric) and IFI-124 (Inch) both specify minimum prevailing-off torque values after 5 removal cycles. Torque typically drops 30 to 50 percent from first to fifth removal. Most manufacturers recommend replacing after 5 to 10 removals depending on application criticality.

Microencapsulated adhesive beads are factory-applied around the full 360-degree thread circumference. During assembly, fastener engagement ruptures the microcapsules, releasing adhesive that chemically bonds to both mating thread surfaces as it cures. Locking is chemical adhesion, not friction. The 360-degree coverage provides uniform locking force across the entire thread contact area.

• Chemical adhesion via adhesive cure after microcapsule rupture during assembly
• 360-degree coverage provides uniform locking force unlike the localized nylon patch
• Breakaway torque (initial break-loose) is typically higher than continuing prevailing-off torque
• Short cure time required for full bond strength after assembly
• Clean, no-mess application; capsules release only at assembly
• Consistent torque performance across the full thread engagement length
• Single-use only; capsules are consumed on first assembly
• Removal and reinstallation yield significantly reduced locking performance
• Shelf life considerations; store per manufacturer guidelines

Preapplied adhesive is a single-use system. Once microcapsules are ruptured and adhesive cures, reassembly without reapplication provides only residual friction. For applications requiring multiple removals, nylon patch is the preferred choice.

Anaerobic liquid adhesive is applied by the assembler directly to fastener threads immediately before installation. In the absence of air and presence of metal ions, the liquid undergoes anaerobic polymerization, forming a rigid thermoset plastic that fills thread voids and chemically locks both surfaces. Unlike factory-applied systems, the assembler controls grade and quantity at point of use.

• Anaerobic chemical cure; only polymerizes when air is excluded between metal surfaces
• Prevailing-On torque is near zero; full locking develops only after adhesive cures
• Breakaway strength is entirely dependent on the product grade selected
• Requires cure time (hours); varies by product, temperature, and substrate
• Locks and seals simultaneously; prevents corrosion and fluid ingress
• Grade selection controls removal difficulty at point of use
• Applied by assembler; process control and operator training required
• Performance highly dependent on surface cleanliness and substrate type
• Passive surfaces (stainless, plated) may require activator primer

Low strength (Blue 242): Removable with hand tools. Ideal for set screws, adjustment fasteners, and frequently serviced joints.

High strength (Red 271): Permanent hold; requires heat (approx. 450 deg F) or special tooling for removal. Use only where disassembly is not anticipated.