How They Work

The locking action, partly produced by friction developed between the pellet and the mating thread, results from the metal to-metal friction opposite the locking pellet. The pellet acts as a wedge and creates a counter-thrust when deformed, while the inherent memory of the pellet strives to regain its original shape, causing positive locking. Since the lock action exists at all times, Tek-Lok fasteners are ideal for “adjusting” applications, when it’s essential that the fastener stays in a specific position without being seated.

Tek-Lok fasteners are produced in both military and commercial grades, and are offered in a variety of insert materials for cryogenic to high temperature applications.



Pellet Materials

For application of Tek-Lok locking pellets to special threaded components, please follow the recommendations below. Remember, Long-Lok Fasteners can manufacture the complete fastening component, or if you prefer, you can send your parts for processing.

1. Specify "Tek-Lok [Nylon, Kel-F®, or Vespel®] Pellet." Add to drawing notes: "to be installed by Long-Lok Fasteners Corporation."
2. If pellet is to be positioned further from the end of the part than standard “L” dimension indicates (see “Standard ‘L’ Dimensions” below), specify as length “E”. It is not necessary to specify “L” if standard length is satisfactory.
3. If pellet must be located diametrically in relation to another point, this location should be dimensioned.
4. If special torque is required, please consult with factory.

The locking pellet locations shown are approximate and for engineering information only.



Applicable Standards

Military Specifications
MIL-DTL-18240

Military Standards
MS15981

Commercial Standards
IFI 124, IFI 524 (Metric)



Female threaded items

All standard nuts and most female threaded items can be made self-locking by drilling through the wall of the part and installing and swaging in place a nylon pellet. In some applications the pellet can be installed from the inside without drilling through the wall. Contact Long-Lok before specifying this design.



Specialty and Hard-to-Engineer Parts

Special parts can be produced with Tek-Lok pellets. Contact Long-Lok’s engineering group for unusual thread sizes, materials, thin wall conditions, short parts—where standard pellets do not appear applicable.



Clearance Hole

The locking element in Tek-Lok commercial fasteners can protrude above the crest of the thread, to approximately .010” over the maximum major diameter of the fastener. Therefore, a clearance hole of about .015” larger than the maximum major diameter of the fastener is recommended to allow for passage of the locking element, and the mating thread should be chamfered .020/.030 over the major diameter to insure good compression and locking action of the insert. Consult factory for special clearance hole or chamfer requirements.



Engagement Revolutions

Ideal performance of Tek-Lok commercial fasteners is obtained when the locking element has engaged the mating thread for five revolutions (threadpitches) or more. However, in many applications excellent performance is obtained with considerably less engagement. In general, the minimum length standard Tek-Lok fastener readily obtained can be determined by noting that two full pitches of thread should exist beyond the locking element (L dimension) for either proper performance or manufacturing ease.



Drilling and Tensile Strength

Extensive, independent test data demonstrates that when used properly, the tensile strength of Tek-Lok pellet type fasteners are not adversely affected by the drilled holes used to accommodate the locking element. Sizes of ¼" diameter and smaller may exhibit a very slight reduction directly in the drilled hole area. However, similar test data has shown that a high tensile strength margin remains; all parts still meet minimum specification requirements. Torsional strength for these parts is only affected in sizes smaller than #8, and then only when tightened beyond yield strength. Shear strength is not lost in any size; high shear bolt grips are not altered.



See for Yourself

Send us a sample of your part or fastener, along with a brief description of its application and performance requirements, and we’ll process it using the most appropriate Long-Lok thread locking or sealing method. Or, to sample a standard Long-Lok fastener, simply supply us with a part number. Samples are provided free of charge. Call your nearest Long-Lok facility for assistance.