Where a standard product does not exactly meet the requirements of a given application then Tappex may already have stock of a special variation that is suitable.

Typically, variations will be in the length or oversize body (i.e. M5 in an M6 body) or head dimensions.

For significantly large order quantities, inserts can often be produced as 'Specials' to the customer's requirements. For advice, please contact our applications department with your specific requirements.

Apart from these many variations on the standard range of inserts, Tappex have developed some specialised products for very particular applications.

SETSERT®
Available as a Single and Double Ended brass insert for press fitting into harder or filled grades of Thermoplastic and Thermoset materials, designed to optimise high volume applications where automatic feed equipment is justified. Please contact us to discuss availability.

SURESERT®
A Double Ended brass insert designed for heat insertion only, the curved knurl form makes it most suitable for stress prone thermoplastic materials. Please contact us to discuss availability.

DEDSERT®
The Tappex Dedsert range of inserts is suitable for heat or ultrasonic installation into Thermoplastic materials. 

The Dedsert design, see image, includes two bands of helical knurling with left and right helix, undercuts and a pilot to assist with insert location.

Particularly suitable where high load capacity is required, the two bands of opposed helical knurling offer a good combination of rotational and pull out performance. 

The Dedsert is initially available unheaded but may be manufactured headed or with a male thread.

Advantages:

• High rotational and pull out performance.
• Rapid heat or ultrasonic installation.
• Short series and headed variants made to customer order.
• Pilot provides a means of alignment with the receiving hole.

The part number is defined 101 for regular and 102 for short length unheaded and 171 for reduced headed, followed by the thread size. Currentlythe range is limited, please contact us with your requirements. 

Knurled Headed Triserts
Tappex has developed, and obtained patent protection for, an enhanced version of the headed Trisert. The knurl feature on the head, and the advantages it offers, may be applied to any Headed or Reduced Headed Female Trisert in the Tappex range.

The product was developed to overcome a particular problem encountered by one of our customers.

The application comprised the fastening together of two plastic mouldings in Aquamid PA6. The heads of the four inserts used were in contact with the mating part when in a clamped condition. The application was required to be regularly serviced “in the field”, with a specified tightening torque of 2.8Nm, using steel M4 set screws, zinc and clear passivated.

The customerwas concerned that the current standard 336M4 Triserts were failing when the unit was serviced, with the inserts stripping and backing out during disassembly.

Testing at Tappex suggested that the application torque of 2.8Nm was sufficient to fail, or partially fail, the inserts by rotation during initial tightening. 

Generally, when a clamp condition is achieved, the friction between the insert head and mating part combines with the features on the insert to resist the rotation generated by the tightening torque. The rotational force comes from the contact between screw thread and insert thread, and its magnitude is related to the applied torque and the friction coefficient between the threads. A number of plastics, including PA6, have lubricious qualities that limit the benefit of clamping against the head.

For this application, the Aquamid PA6 mating part offered little extra rotational resistance, the onset of insert rotation and failure being measured at approximately 1.5Nm.

To overcome this problem, a radial knurl has been added to the top surface of the 336M4. (See image)

Now, when the torque is applied, drawing the face of the PA6 mating part into contact with the knurled head on the Trisert, the knurled feature bites into the surface of the plastic of the mating part, dramatically increasing the insert’s resistance to rotation. Likewise on disassembly, the subsequently visible,indentation of this feature into the mating part prevents the insert backing out with the screw.

Further testing revealed that the modified insert is capable of withstanding in excess of the required 2.8Nm without rotation.

The magnitude of the gain in rotational resistance relates to the frictional characteristics of the mating part material and the clamping condition. Testing would be required to quantify this with other applications and plastics.

General Requirements:

• The mating part must be clamped against the head of the insert.
• The material of the mating part must be deformable enough to ensure the knurled feature bites into it at the applied torque.
• The components being fastened together should not be able to rotate with respect to one another around the axis of the insert. Single insert applications must be carefully designed to prevent this.

Triserts have been specifically designed for ease of use, and for speed of installation into both Thermoset and Thermoplastic materials, and has also been designed to meet the needs of new types of engineering plastics. Tappex offer pneumatic reversible tools mounted in a flexible pantograph arm. A Tappex Production Driver (part no.029) should be used for installation. Also available from Tappex is the Hand Installation Tool (part no. 031) for use with small quantity installations.

Vandlgard®
Tappex tamper proof break off fastening system to guard against theft or vandalism.

In this day and age the design of many mechanisms and products is not complete without the inclusion of some contingency for the prevention of possible theft and vandalism; the Tappex VANDLGARD NUT is a new way of meeting this requirement.

By combining subtle design with simplicity of application, use of the VANDLGARD NUT provides a different alternative to standard female fasteners whenever a nut would otherwise be left exposed.

The hexagonal portion of the VANDLGARD NUT is designed to break away from the threaded conical shaped body at a predetermined torque leaving in place a tamper proof and properly torqued nut. This ensures that equipment, parts and protective devices cannot be removed or stolen.

Design Aids

• No special tooling required for installation
• More secure than fasteners that rely on a tool with unusual geometry
• Easier to service than riveted or welded joints
• Conical shape gives attractive cosmetic appearance
• Easily installed in remote field applications
• Anodised aluminium material minimises corrosion
• Engineered break off ensures controlled torque settings