Threaded Inserts for Plastics Design Guide
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WHY INSERTS? Inserts provide reusable threads and secure tight threaded joints. An additional benefit is high load carrying capability. PRESERVATION OF THE THREADED JOINT The primary benefit for using an Insert is that it preserves the threaded joint integrity for the life of the application. An additional benefit is the unlimited reusable thread. PROPER SEATING TORQUE During the assembly process with a mating component, the screw has to be tightened with sufficient torque to introduce the recommended axial tension in order to achieve the required load between the screw and Insert threads...

TECHNICAL SUPPORT Since SPIROL’s inception in 1948, we have lead the industry in application engineering support for fastening, joining and assembly. Our Inserts are designed to maximise and balance tensile (pull-out) and rotational torque performance. Our Application Engineers have the technical knowhow and experience to work together with our customers to develop a cost-effective solution to meet the application requirements. BROAD PRODUCT RANGE/CAPABILITY Our leading edge production technology is suitable to meet all your specific needs for both long and short run requirements at...

INSERT DESIGN The objective is to design an Insert with sufficient torque resistance to accommodate the tightening torque necessary to achieve sufficient axial tension load on the threaded joint to keep it together and prevent loosening, while also achieving pull-out values necessary for the load conditions that the Insert will be exposed to while in service. In general, resistance to torque is a function of diameter and resistance to pull-out is a function of length. These functions, however, are interactive and the challenge for the designer is to achieve the optimum combination of both....

SELF-TAPPING INSERTS Provide the best pull-out resistance for a post-mould installed Insert. The threads are designed with a thin profile to minimise inducing stress into the plastic and a relative coarse pitch to provide the maximum plastic shear surface to resist pull-out. Installation torque is not a problem in that tightening increases the friction between the plastic and threads, and the larger diameter of the external Insert thread increases the frictional surface. Back-out torque performance relies totally on the greater surface area of the external Insert thread and the tension...

PLASTIC OVERVIEW There are four main commercial categories of plastics: thermoset, thermoplastics, foam and elastomers. The latter two have limited suitability for Insert installation and should an Insert be required, an application analysis is suggested. Accordingly, these categories are not covered here. Thermoset plastics, once formed, undergo an irreversible chemical change and cannot be reformed using heat and pressure. These plastics are tough and heat-resistant. Examples are Bakelite, urea and polyester resins. Heat/ Ultrasonic Inserts are not suitable for these plastics. Thermoset...

DESIGN GUIDELINES l Holes for post-mould installed Inserts should always be deeper than the length of the Insert. For Self-Tapping Inserts, a minimum depth of 1.2 times the Insert length is recommended. For other Inserts, the recommended minimum depth is the Insert length plus two (2) Insert thread pitches. The assembly screw should never bottom out in the hole, as jack-out would result. l Counterbores are not recommended for any Insert types except Self-Tapping and Headed Inserts. Counterbores are recommended for Self-Tapping Inserts to reduce the risk of flaking. The outside diameter of...

l Post-mould installed Inserts that are cold-pressed into the hole require larger boss diameters and/or wall thickness to withstand the greater stresses induced during installation. Installing the Inserts while the plastic is still warm from the moulding process generally eliminates this need. Incorrect Incorrect Incorrect l The diameter of the clearance hole in the mating component is very important. The Insert and not the plastic must carry the load. The hole in the mating component must be larger than the outside diameter of the assembly screw but smaller than the pilot or face diameter...

SPIROL INSERTS SPIROL has a broad range of Inserts for post-mould installation as well as a series of Moulded-In Inserts. Installation of Inserts after moulding reduces in-place cost by shortening moulding time and eliminating secondary cleaning. This method also reduces rejects and mould damage resulting from dislodged Inserts. Moulded-In Inserts are placed into the mould cavity prior to plastic injection and offer exceptional torque and pull-out resistance due to unrestricted plastic flow. HEAT/ULTRASONIC INSERTS are designed for post-mould installation in thermoplastics. Heat and...

HEAT-ULTRASONIC INSERTS STRAIGHT HOLE SERIES Inch Metric Conversion Thread Size Short Length Long Length Head Thickness Recommended Hole Design* L + 2 Thread Pitches * ee page 5 for more information S on recommended hole design To Order: INS (Series #)/Thread Size / Length, Material, Finish Examp

HEAT-ULTRASONIC INSERTS STRAIGHT HOLE SERIES Thread Size Inch Metric Conversion Short Length Long Length Head Thickness Recommended Hole Design* L + 2 Thread Pitches * ee page 5 for more information S on recommended hole design To Order: INS (Series #)/Thread Size / Length, Material, Finish Example: INS 2

HEAT-ULTRASONIC INSERTS TAPERED HOLE SERIES Thread Size Inch Metric Conversion Thread Size Recommended Hole Design* L + 2 Thread Pitches To Order: INS (Series #)/Thread Size / Length, Material, Finish Example: INS 14/8-32 / .312L

SELF-TAPPING INSERTS Reduced thread profile and coarse pitch minimises radial stress and potential hole wall damage. The coarse thread also maximises the pull-out strength of these Self-Tapping Inserts. Series 10 Thread Forming L DIMENSIONAL DATA Thread Size Inch Metric Conversion Counterbore Depth Recommended Hole Design* * ee page 5 for more information S on recommended hole design To Order: INS (Series #)/Thread Size / Length, Material, Finish Example: INS 10/250-20 / .43