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Hardened Steel Screw-Serts

The PSM Hardened Steel Screw-Serts have been designed to provide a hardened steel thread in the softer aluminium and zinc based diecastings, magnesium and thermosetting plastics. The external thread cuts into the parent material reducing radial stresses in the casting.

Advantages

Design Guide

Hole Preparation

Hole diameter will vary with the type of material used. For this reason the data table shows the hole size ranges for the different material classes.

Holes may be cored or drilled. The taper on a cored hole should be 1° inclusive and the hole diameter should apply at the point reached by the bottom of the insert. A 60° countersink at the top of the hole is strongly recommended in order to avoid the risk of chipping to the surrounding surface. The depth of the countersink should be equal to the external thread pitch of the insert. The depth of blind holes must be a minimum of 1.2 x insert length.

Installation

Form a hole in the material to size recommended and install the fastener square in the hole. Apply pressure to the head of the fastener sufficient to totally install the broaching feature into the board, locking the fastener securely in place. Insert fixing screw or bolt from side opposite to the fastener head.

Wall Thickness

The minimum wall thickness will vary with the ductility of the diecasting alloy, but as a general guide wall thickness should not be less than the nominal thread diameter. Specific use of materials like magnesium and applications requiring thinner boss walls may require subtle changes to the design of the insert. In either case consultation with the PSM Technology Centre or local sales office and pre-production testing is essential.

Type of Loading

Direct torque loads should be avoided with this type of insert.

Technical Data

Hardened Steel Screw-Serts (SCT)

STANDARD MATERIAL
Case Hardened Mild Steel

Dimensional References

How to Specify

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Frequently Asked Questions About Hardened Steel Screw-Serts

What is a hardened steel screw-sert?

A hardened steel screw-sert (SCT series) is a self-tapping threaded insert designed for installation into hard or difficult-to-thread base materials such as hardened steel, cast iron, sintered metals, and ceramics. Unlike standard thread inserts that rely on the parent material for thread strength, a hardened steel screw-sert cuts its own external thread into the host material on installation and provides a fully formed, durable internal thread for accepting a machine screw or bolt. PSM’s SCT series is engineered specifically for applications where conventional tapping would fail or produce inadequate thread life.

How does a hardened steel screw-sert work?

A hardened steel screw-sert works in two stages. First, a pilot hole is drilled in the host material to the specified diameter — no pre-tapping is required. The screw-sert is then driven into the hole using a suitable installation tool; as it advances, its hardened external thread cuts directly into the host material wall, locking itself firmly in place. The result is a strong, permanent internal thread (the internal metric thread of the insert body) that can accept a standard machine screw. The insert’s knurled or serrated shank profile prevents rotation and push-out under load.

What materials can hardened steel screw-serts be installed into?

Hardened steel screw-serts are engineered for materials that are too hard or brittle for standard thread inserts. They can be installed into hardened steel, cast iron, powdered metal (sintered) components, hard aluminium alloys, ceramics, and other special materials where conventional tapping tools would wear prematurely or fail entirely. The SCT’s case-hardened body is harder than most host materials, allowing it to self-tap a secure external thread on insertion. Always consult PSM’s technical specifications to confirm compatibility with your specific base material hardness.

What industries use hardened steel screw-serts?

Hardened steel screw-serts are used across a wide range of industries where fastening into hard or special materials is required:

Automotive & motorsport — fastening into cast iron engine blocks, hardened gear housings, and sintered metal components
Mining & heavy equipment — re-threading stripped or damaged threads in hardened wear parts
Defence & aerospace — reliable threaded connections in high-strength, difficult-to-machine alloys
Industrial machinery — thread repair and insert installation in hardened tool steel fixtures
Electronics & precision engineering — fastening into ceramics and hard anodised aluminium
General thread repair — restoring stripped threads in hardened components where re-tapping is not possible

Do I need a special installation tool to fit a screw-sert?

Yes. Hardened steel screw-serts require a specific installation driver or mandrel matched to the thread size and insert type. The driver engages the internal thread of the insert and applies the controlled torque needed to cut the external thread into the host material without over-driving or damaging the insert. Using an incorrect tool risks stripping the insert’s internal thread or failing to achieve full seating depth. PSM can advise on the correct installation tooling for each SCT part number — contact the PSM technical team for guidance.