Insert Technology For Plastics, Composites And Metal Alloys

The Tappex Trisert range of inserts for plastics has been developed for various environments and application criteria. It includes three primary designs – Double ended, Reduced headed and Headed, all available as Normal limit and Close limit.

Double Ended – Product Features

Three primary and three secondary equidistant cutting flutes over the length of the external form, give a more balanced cutting load than other forms of self-tapping insert. The cutting action takes place at a larger number of points on the thread form over the length and circumference of the insert.

Lead on both ends allows the insert to be installed either way up, therefore, where the volumes dictate that bowl feeding equipment is required, it is not necessary to incorporate complex flighting systems to orientate the insert, which makes bowl feeding simpler and reduces tooling costs.

Free running internal thread due to there being no interruption to the internal thread, as the external longitudinal flutes produce the cutting action during installation.

Reduced outward stress – During the installation process the cutting action of self-tapping inserts results in slight outward stress. This is reduced to an absolute minimum with the Trisert and enables the insert to be used in brittle materials and also where there are thin walls.

Improved axial alignment – The balanced cutting load of the Trisert reduces side thrust caused by predominantly only one cutting edge. This has the effect of guaranteeing much closer axial alignment of the insert in the hole.

Design Aids

• In conjunction with the six cutting flutes, greater interference can be achieved by the special truncated thread form, increasing radial and pull out performance. The coarseness of the external thread retains a greater proportion of the predominantly weaker parent material improving the performance of the insert and allowing shorter standard lengths to be specified.
• The Trisert is available in three standard lengths – short length for applications where space is limited, regular length, and long length for maximum pull out loading in all applications.
• Due to the Triserts coarse thread form, the greater helix angle of the thread produces a greater resistant component of force radially, and increases the radial stripping torque of the insert. It is possible to stall torque the Trisert at the bottom of the hole increasing the locking action for applications subject to vibration.
• One of the disadvantages of the slotted design of some self-tapping inserts is that the accumulation of swarf at the bottom of the insert can cause contamination of the insert's internal thread. The Trisert eliminates this problem as the majority of loose material is trapped in the cutting flutes.
• Trisert Advanced should be specified where thin walls or thermoset materials are required and mean the interference between insert and material must be tightly controlled.
• The Trisert is a perfect cylinder, which has not been weakened by a transverse slot. It is therefore stronger than an equivalent slotted insert and will not collapse when being installed into hard or abrasive materials. This means that the Trisert can be produced in smaller diameters and extends the range of potential applications in reduced diameter bosses and where space is limited.

Reduced Headed – Product Features

The reduced headed version of the Trisert incorporates the same special truncated thread form containing three primary and three secondary equidistant cutting flutes, but provides the designer and production engineer with a higher performance flush fitting insert to match product availability to common assembly problems.

Reduced head at the same diameter as the external truncated thread form provides an increased bearing surface.

Reduced Headed – Design Aids

• It should be specified where a flush fit finish is required.
• It should be specified where higher tightening torques are required.
• The head helps to prevent jack out where elongated slots or slightly oversize holes are necessary in mating components.

Headed – Product Features

The headed version of the Trisert incorporates the same special truncated thread form containing three equidistant cutting flutes, but provides the designer and production engineer with standard options to match product availability to common assembly problems.
Large diameter head prevents jack out in applications where elongated slots or larger than standard clearance holes are necessary in the mating component. It has a larger bearing surface that is required in high torque applications.

Headed – Design Aids

• It should be specified in applications where increased resistance to rotation is required.
• It also provides an excellent conductive surface for electrical contacts, ring connectors or eyelets.
• The large head diameter helps to prevent jack out in applications where elongated slots or larger than standard clearance holes are necessary in mating components.

Installation

The Tappex Trisert can be installed using our specifically designed Tappex FlexiArm, used in conjunction with our production drivers, which provides a method of accurately installing inserts at various heights and positions in a moulding. Click on the installation video below to see the FlexiArm in use. Alternatively they can be installed by hand using our 031 range of Hand Installation Tools that come complete with alignment bushes to aid correct installation. Please contact our applications department for further information and details.