Reusable Metal Threads


SI inserts permanently install in plastic assemblies to provide durable and reusable metal threads for mating hardware and allow for repeated disassembly and re-attachment whenever required. By promoting quick and easy access to an assembly, SI inserts offer highly practical joining solutions in contrast to fixed and unyielding methods, such as adhesives or rivets. Repeated reuse will not damage the strong metal threads or compromise attachment integrity. Types include brass inserts and lead-free stainless steel and aluminum versions.


Applications include consumer electronics (wearables, smart phones, and handheld devices) and plastic equipment or components for the medical, automotive, aerospace, transportation, and recreational industries, among many others.


All SI inserts install permanently in plastic, offer unique features, and can be classified generally by installation method. Depending on series, inserts can either be ultrasonically pressed and/or heat staked, molded-in during the injection molding process, or cold pressed into a pre-molded or drilled hole.


SI inserts can be specified in unified or metric thread sizes and in a variety of designs and lengths – including SI microPEM inserts with threads as small as M1.


Detailed specifications, fastener drawings and 3D models, and performance data (Bulletin SI) for these RoHS-compliant fasteners can be viewed and downloaded for free at


Line for plastic assemblies includes:

  • ultrasonic / heat staking inserts for installation ultrasonically or with a thermal press
  • molded-in types installed during the molding process
  • press-in types installed by pressing the insert into a pre-molded or drilled hole
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