Mold-in Inserts

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Mold-in inserts are components that are inserted into a molded part during the manufacturing process. They are permanently encapsulated within the molded part and provide a way to add threads or attachment points to a composite material. This allows the secure fastening of other components, such as screws, bolts, or other threaded parts, to what was previously non-threaded material.

Also known as rotational molding or rotomolding inserts, molded-in inserts are inserted into the mold cavity before the injecting process begins. The molten injection material surrounds the insert, encasing it and forming the desired shape. Once the injection cools, the mold-in inserts are firmly embedded and solidified into the material.

Rotaloc designs and manufactures a full range of standard and custom mold-in inserts. For more information, view our resource guide or contact us today to find fitting rotomolding inserts for your project.

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Types of Inserts

Rotaloc carries an extensive line of mold-in inserts designed for various applications. Each insert is designed for specific purposes, so understanding each is essential in choosing the correct model for your application.

Bonding Fasteners

Bonding fasteners are baseplates designed to be over-molded or bonded onto almost any substrate. Their surface area creates a secure hold and distributes load forces. They are available in various styles and sizes, commonly formed with stainless steel and zinc coatings.

Hex Inserts

Hex inserts are hexagonal and feature internal threads with a hexagonal cross-section. They are machined from hex-shaped bar stock and are one of the most common mold-in inserts. They are commonly made from brass, aluminum, steel, or stainless steel.

Square Inserts

Square inserts feature a square shape and are compatible with square-drive fasteners and bolts. Their shape offers stability and helps maintain the proper alignment of the insert within the molded part. Square inserts are typically made with aluminum, brass, or multiple grades of stainless steel.


Geoserts are a Rotaloc original. They offer the greatest torque strength, pullout strength, and material flow of all inserts. They are produced using stainless steel or zinc-plated mild steel.

Round Knurled

Round knurled inserts feature round bodies with a knurled outer texture, typically in the form of diagonal or diamond-shaped ridges. This texture enhances grip and prevents rotation. They are usually composed of brass, aluminum, zinc-plated steel, or stainless steel.

Specialty Inserts

Specialty inserts are designed for particularly unique applications. They are tailored to meet specific requirements and challenges for various industries. These inserts can be produced from titanium, brass, aluminum, mild steel, or stainless steel.

T-Nuts & Nutserts

T-nuts and nutserts are similar in threading but vary in shape. T-nuts are pronged molded-in inserts with T-shaped bodies and threaded barrels. The T-shape and prongs increase grip and keep the insert in place. Nutserts are cylindrical with internal threading and are helpful in applications with limited installation space.

NPT & SAE Inserts

NPT and SAE inserts are similar inserts designed for different applications. NPT (National Pipe Thread) inserts are designed for pipe fittings in North America. SAE (Society of Automotive Engineers) inserts are designed for automotive assemblies. They are usually made from carbon steel, stainless steel, brass, or aluminum.

Industrial Applications

Rotomolded inserts can be found in many industries, including:
  • Electronic
  • Automotive
  • Plumbing
  • Marine
  • Medical

Benefits of Molded Part Inserts

Molded-in inserts are useful for many industrial applications. Some of their advantages include but are not limited to:
  • Improved strength
  • Versatility
  • Time and cost savings
  • Increased load-bearing capacity
  • Enhanced design and aesthetic options

Rotaloc is Your Trusted Supplier of Molded-In Inserts

With our extensive supply of metal and plastic mold-in inserts, Rotaloc will have the right tools for all your custom insert needs. Our team of experts is prepared to assist you with insert selection or any questions.

Contact us today and let us help you with your mold-in insert applications.