Stainless steel thread inserts for critical applications

The standard Trisert range has for many years included three primary designs, Double Ended, Reduced Headed and Regular Headed variants. These solve most application problems in thermoset and thermoplastic grades, including the latest engineering plastics.

Reliable and strong thread inserts

The concept of the Trisert design is to provide a reliable and efficient post-mould process, where the installation torque can be controlled and monitored for greater reliability. As the internal thread is used to install the Trisert, every insert is therefore automatically checked in the moulding for the existence of a good thread.

Trisert-3 is the latest addition to this family and has been developed to expand the proven Trisert range into more critical applications.

Trisert-3 - Features

Trisert 3 Features

Trisert-3 has three cutting features to provide more balanced cutting forces and therefore reduced installation torque, compared to the many cross-slot designs available, that only have two cutting features.

The Trisert-3 design maintains the complete cylinder design that provides a stronger body, size-for-size, than the slotted design and also allows it to be used in pull-through applications, without any problems due to increased assembly torque associated with slotted inserts.

Trisert-3 is available in two lengths - regular and long - and is based upon the Trisert Reduced Headed design. This provides an increased bearing surface that not only allows higher tightening torques to be applied, but also provides more support to softer mating components. The head diameter is designed to exactly fit the counter bore in the prepared hole, and thus presents a neat flush fit finish, where required.

Material grades

In most applications into plastic, the standard brass Trisert offers a satisfactory and economic solution with good wear resistance and strength. Also it will withstand corrosion in most environments without any second operation surface treatment.

In order to meet the requirements of a wider range of host materials and harsher applications, the selection of the material for the Trisert-3 was very important. Thus the Trisert-3 is offered in two grades of Stainless Steel (303 and 316) and also in case hardened steel with a zinc nickel, trivalent passivated finish.

A key feature of the Trisert-3 is its ability to withstand critical environmental conditions, such as marine and chemical/food processing, while still retaining good wear resistance and strength.

Trisert 3 - Installation

Flexiarm installation equipment

The Tappex FlexiArm provides a rapid and reliable method of installation for the Trisert-3 range. The FlexiArm installation machine consists of a pantograph arm with a pneumatic screwdriver attached. The screwdriver can be specified with an automatic reverse torque-clutch control at either 510 rpm or 1,100rpm, or a manual reverse torque-clutch control at 510 rpm, depending upon the size of the insert and the material into which it is being installed.

The FlexiArm provides a low-cost assembly solution for many different post-mould applications and its size allows it to be installed alongside the respective moulding machine, so that inserts can be fitted during the waiting time of a typical mould cycle. It is available with one, two or three arms (which can be fitted at a later date) to suit most multi-task assembly requirements.

With harder materials it is more critical that the insert is exactly aligned with the receiving hole. The latest Tappex FlexiArm facilitates this by being adjustable in two planes.

A range of production drivers is available to provide an accurate method of installing the inserts at various heights and positions in the moulding (see inset), and they are available separately to suit M3 to M10 threads and also equivalent Imperial sizes.

Hand Installation Equipment

Alternatively, the inserts can be installed by hand, using the 031 range of Tappex Hand Tools that come complete with an alignment bush to ensure correct installation.




Trisert-3 - Reduced Headed - 6238M3

Material: 316 Stainless Steel, 303 Stainless Steel and Steel Case Hardened Zinc Nickel plated and Trivalent Passivated.
These materials are RoHS compliant.

Finish: Self-Colour Passivated and as specified. Special finishes to customer requirements, at extra cost.

Description: The Trisert-3 is a single ended self-tapping insert. Its main features are the truncated external thread form with three equally spaced cutting facets.

Application: Designed to meet the the requirements of a wide range of host materials and harsh environments where brass Triserts would not be suitable. The Trisert-3 is compatible with the hole size for the equivalent size standard Trisert. Suitable in corrosive atmospheres and for installation into alloys or particularly hard engineering plastics.

Hole Size: Moulded and drilled hole diameters vary dependent upon installation technique, specific component geometry and material. Please consult our technical department for a precise recommendation, to ensure optimum production conditions. Sizes given are for reference purposes only.

Hole Design: The hole design information is intended to indicate the approximate dimensional requirements for satisfactory installation of the insert. They should not be specified for production tooling without prior consultation with our Application Engineering Department - we accept no responsibility should the use of this information without consultation result in product failure. Please call our application engineers for assistance +44 (0) 1789 206600

Installation: Self-tapping using a hand tool (part no.031) or reversible drive mechanism. Tappex offer pneumatic reversible tools mounted in a Tappex FlexiArm, used in conjunction with a Tappex production driver (part no.029).


Trisert-3 - Reduced Headed - 6238M3 (Insert design) Trisert-3 - Reduced Headed - 6238M3 (Hole design)

Insert design

Part No.: 6238M3
Thread Size: M3
Pitch (internal):0.50
Diameter (external) B:4.73
Head Thickness T:0.38
Head Diameter D:4.70
Length L:5.25

Hole Design

Hole Diameter C (Plastics):4.10-4.40
Hole Diameter C (Alloys):4.35-4.55
Hole Depth Y: 5.80
Boss Diameter X: 7.70
Wall Thickness W: 1.65


The following are downloads relating to the Trisert-3 range, although a downloads may also be applicable to other product ranges. General information can be found on our downloads page.

If you can't find what you are looking for, why not try our chat facility where one of our helpful team can assist you or simply give us a ring on +44 (0) 1789 206600.