How to Choose the Right Threaded Insert for an Application

    HTF offers a wide variety of press-in, molded-in, as well as ultrasonic/heat staking inserts. What is the best threaded insert for the type of application needed? By reviewing the different types of threaded inserts as well as the application and materials involved, we hope to help you answer that question. 

    Common Types of Threaded Inserts

    Hexagonal Inserts (Types NFPA, NFPC)

    Hexagonal inserts are a cold pressed-in insert in both aluminum and stainless steel varieties. They provide strong, reusable threads with no heat or ultrasonics required for insertion. The hexagonal “barbed” configuration promotes high torque-out and pullout values. 

    Blind Threaded Inserts (Types IBA, IBB, IBC)

    These inserts come in stainless steel, brass, and aluminum with a blinded end, which protects the threads from plastic intrusion. 

    Self-locking Blind Threaded (Type IBLC)

    These stainless steel inserts have deformed threads to lock the screw in place and resist vibration. The blind end protects the threads from plastic intrusion. 

    Thru-threaded (Types ITA, ITB, ITC)

    Thru-threaded inserts include a pilot diameter and undercuts which allow the plastic to flow into grooves, providing high pullout resistance. These inserts come in aluminum and brass varieties. 

    Knurled Spacers (Types STKA, STKB, STKC)

    These thru-threaded, knurled spacers come in aluminum, brass, and stainless steel and include a uniform knurl diameter to reduce the risk of sink marks. They are available in varying lengths for injection molding assemblies.

    Tapered (Types IUA, IUB, IUC)

    Tapered, thru-threaded inserts in aluminum, brass, and stainless steel are designed for use in tapered holes. The tapered mounting hole allows for rapid and accurate alignment prior to installation. 

    Flanged (Type PFLA, PFLB)

    The flange-head inserts available in aluminum and brass are press-fit with strong, reusable threads. They are cold pressed and do not require heat or ultrasonics for installation. The flange head eliminates direct contact of plastic with mating parts. The slotted insert compresses allowing access into the mounting hole. 

    Straight Wall (Types IUTA, IUTB, IUTC)

    These straight-wall, thru-threaded inserts are designed for use in straight holes. The self-aligning lead-in of the inserts provides for accurate alignment prior to installation. Straight-wall, thru-threaded inserts are available in several materials including aluminum, brass, and stainless steel. 

    Consider the Application and Materials

    Torque-out and Pullout Values

    Essential to choosing the proper threaded insert for a plastic assembly is the torque. Longer threaded inserts have greater pullout capacity while an insert with a wider diameter will have improved overall torque-out capacity.

    Plastic Applications

    Threaded inserts are primarily applied to two types of plastic materials — thermoplastics and thermoset plastics. Thermoplastics can be melted and recast continually. Thermoplastics become like liquid when melted and solidify when cooled.

    Thermoplastic insertion approaches include heat-staking and ultrasonic methods. Thermoset plastics are molded using a permanent chemical reaction caused by the use of heat, pressure, and time. Once the Thermoset plastic materials set, they cannot be altered like thermoplastics. Insertion applications include molding-in and cold insertion.

    • Lead-free Alternatives — Aluminum and Stainless Steel inserts offer a lead-free alternative for threaded inserts with plastic applications. 
    • Ease of Use — Cold pressed-in threaded inserts (thermosets) utilize the most cost-effective and easiest insertion method that requires a basic press for execution. The inserts are simply pressed into the thermoset plastic mold resulting in a weaker bond and overall strength, but generally is a sturdy alternative that will work and be less costly than heat-staking or ultrasonic assisted threaded inserts. 
      • Self-aligning lead-in for threaded inserts provides for accurate alignment prior to installation.
      • Symmetrical, thru-threaded inserts eliminate the need for orientation during installation.
      • Pressed-in options do not require heat or ultrasonics for installation making them the easiest option.

    HTF offers a wide variety of threaded inserts for all plastic applications and can perform same day shipping on most orders. With worldwide distribution and strong partnerships allowing for a vast selection, HTF is the global leader in threaded insert offerings. Reach out today, we are here to help.

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