Poly-Lok® Patch Type

-100°F to +400°F
Reusability greater than IFI 124, IFI 524 and MILDTL-18240
Made of polyethylene terephthalate

Poly-Lok® is today’s most advanced, most reliable prevailing torque type self-locking fastener. And it’s all due to the unique polyester patch material that is more resilient, has higher strength, and can be reused more often with higher retained torque values than any other patch material.


Vibration and Shock Resistance.
The Poly-Lok self-locking principle incorporates a polyester patch permanently bonded to the fastener threads. When mating threads are engaged, the polyester patch is compressed. The coefficient of friction and modulus of the material as well as the patch volume controls the prevailing torque value achieved. The added prevailing torque keeps the parts locked together. Poly-Lok fasteners won’t work loose even under extreme shock and vibration conditions.

Elevated Temperature Capability.
Other plastic additive type self-locking fasteners have limited temperature range capabilities. The Poly-Lok patch has changed all that. It can maintain torque and clamp-load performance through a temperature range of -100ºF to +400ºF.

Built-In Thread Seal.
The Poly-Lok patch acts as a dam to prevent liquid leakage along the thread helix. It provides excellent sealing properties between the load bearing and non-load bearing flanks of the mating threads. The Poly-Lok patch formulation is impervious to most chemical solutions, acids, solvents, oils, brake fluid, and anti-freeze solutions. It can withstand hydraulic pressures and offer effective sealing properties with most liquids.

Low Sensitivity to Thread Fit Variations.
In any mass assembly operation, a Poly-Lok patch offers the best of both worlds. Poly-Lok fasteners lock whether seated or not, and the resiliency and strength of the locking polyester patch is insensitive to thread fit variations. They conform to all 2A-2B and 3A-3B thread fitting tolerances within IFI 124, IFI 524, MIL-DTL-18240 and NAS1283 torque requirements.

Poly-Lok Patch is Non-Toxic.
Unlike other patch type locking methods Poly-Lok is non-toxic. This allows its use in applications where toxicity is a problem, such as food processing equipment.

Superior Outgassing Performance Capability.
Poly-Lok products have been approved by NASA for space and vacuum environment applications requiring low outgassing characteristics. They have been tested and proven to meet and exceed the requirements of ASTM-E-595-93 and NASA SP-R-0022A test specifications.

Extended Reusability Feature.
Use of the specially processed Poly-Lok™ II patch provides extended reusability characteristics far exceeding those required by IFI 124 of MIL-DTL-18240. Under ideal conditions, Poly-Lok II has demonstrated over 300 cycle reusability.

Custom Applications and Internal Thread Forms.
Its unique application process enables the Poly-Lok patch to solve almost any type of thread locking problem, including internal thread forms. In fact, Poly-Lok is widely used on hex nuts to provide the special torque, high temperature, or outgassing properties required. In addition, special lengths of the polyester locking material…special thread fit tolerances…special torque requirements or clamp loads…or related mating part characteristics can be specified.

Military Specifications

Military Standards
MS15981, MS16995-16998, MS18063-18068, MS18153, MS18154, MS21090-21099, MS21262, MS21295, MS51021, MS51023, MS51029, MS51031, MS51095, MS51096, MS90727, MS90728

Aerospace Standards
NAS662, NAS1081, NAS1161-1168, NAS1171-1178, NAS1181-1188, NAS1189, NAS1190, NAS1191, NAS1223-1235, NAS1283, NAS1351, NAS1352, NAS1635, NAS1741, NAS1742, NAS1743, NAS4104-4116, NAS4204-4216, NAS4304-4316, NAS4400-4416, NAS4500-4516, NAS4600-4616, NAS5000-5006, NAS5100-5106, NAS5200-5206, NAS5300-5306, NAS5400-5406, NAS5500-5506, NAS5600-5606, NAS5700-5706, NAS5800-5806, NAS6203-6220, NAS6303-6320, NAS6403-6420, NAS6500-6506, NAS6603-6620, NAS6704-6720, NAS6804-6820, NAS6900-6906

Commercial Standards
IFI 124, IFI 524 (Metric)

Test Specifications

Thread Size#0#1#2#3#4#6#8#101/4
"L" Patch Length1/81/81/81/83/163/163/161/45/16
Thread Size5/163/87/161/29/165/83/47/81
"L" Patch Length5/163/81/21/21/25/85/85/83/4
MaterialColor CodeOperating Temperature RangeMaterial Specification
PolyesterGreen-100ºF to 400ºF
-73ºC to 204ºC
AMS 3612


Long-Lok is part of Novaria Group, a cohesive family of precision component companies, that consistently delivers optimum performance and sustainable growth within the aerospace and defense marketplace.
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