Fast Shipping

Bulk Discounts

Over 10,000+ Product Variations

Trusted by 100,000+ customers

Fast Global Shipping

Bulk Discounts

Over 10,000+ Product Variations

Trusted by 100,000+ Customers

Hardened Steel Screw-Serts

PSM Screw-Sert inserts are self-tapping metallic inserts designed to form their own threads in thermoplastic or thermoset materials, enabling a durable steel thread in plastics that otherwise may be too weak to hold repeated screw cycles. They are especially useful in applications where high pull-out loads, jack-out resistance, or weak core strength plastics are involved.

Advantages

Key Features

Self-tapping: no pre-tapped hole is needed; the insert cuts or broaches its own thread as it’s driven in
High pull-out resistance: designed to resist being pulled from the plastic under load
Excellent torque-out strength: capable of withstanding twisting or loosening forces
High reusability: steel thread enables multiple screw cycles without degrading performance
Accommodates weak plastics: suitable for substrates with limited core strength
Flanged and stud versions available to suit different assembly geometries

Selection of Inserts

ISO Metric

Nut Size	Material Thickness mm	Cold Rolled Mild Steel
Nut Size	Material Thickness mm	Push-out Kn	Pull-out Kn	Torque-out Nm
M5	0.7	3	4	9
	1	7	7	9
	1.5	9	10	9
M6	0.7	3.9	4.7	19
	1	7.3	7.4	19
	1.5	11.9	11	19
	2	14	11.5	19
M8	0.7	4.8	4.5
	1	6.5	9.7	36
	1.5	13.1	16	36
	2	17	16	36
	2.5	27.9	18	36
M10	1	7.3	9.6
	1.5	10.8	15.2	80
	2	16.7	20	81
	2.5	28	20	84
	3	29	20	86
M12	1.5	26	18	100
	2	44	24	114
	2.5	44	28	140
	3	45	31	140

Other lengths possible on quotation.

Unified

PRODUCT CODE	THREAD SIZE	INSERT LENGTH A	STUD LENGTH (FOR SCTS ONLY) S										HEAD HEIGHT B	HEAD Ø C	INSERT Ø D MAX	FOR THERMO PLASTICS REC. HOLE SIZE -0.000 +0.004	REC. HOLE SIZE FOR THERMO SETTING -0.00 +0.10	MIN. WALL THICKNESS
SCT-B HSCT-B SCTS-B	2-56	.236	3/16	1/4	5/16	3/8	7/16	1/2	5/8	3/4	7/8	1	.023	.236	.177	.157-.161	.161-.169	EVALUATED BY PRE- PRODUCTION TESTS
	4-40	.236	3/16	1/4	5/16	3/8	7/16	1/2	5/8	3/4	7/8	1	.023	.236	.177	.157-.161	.161-.169
	6-32	.315	3/16	1/4	5/16	3/8	7/16	1/2	5/8	3/4	7/8	1	.029	.295	.236	.209-.213	.217-.224
	8-32	.315	3/16	1/4	5/16	3/8	7/16	1/2	5/8	3/4	7/8	1	.035	.312	.256	.228-.232	.217-.224
	10-24	.394	3/16	1/4	5/16	3/8	7/16	1/2	5/8	3/4	7/8	1	.042	.374	.315	.283-.283	.287-.299
	10-32	.394	3/16	1/4	5/16	3/8	7/16	1/2	5/8	3/4	7/8	1	.042	.374	.315	.280-.283	.287-.299
	1/4-20	.551	3/16	1/4	5/16	3/8	7/16	1/2	5/8	3/4	7/8	1	.052	.472	.394	.339-.346	.354-.370
	1/4-28	.551	3/16	1/4	5/16	3/8	7/16	1/2	5/8	3/4	7/8	1	.052	.472	.394	.339-.346	.354-.370
	5/16-18	.591	3/16	1/4	5/16	3/8	7/16	1/2	5/8	3/4	7/8	1	.052	.551	.472	.417-.425	.433-.449
	5/16-24	.591	3/16	1/4	5/16	3/8	7/16	1/2	5/8	3/4	7/8	1	.052	.551	.472	.417-.425	.433-.449
	3/8-16	.709	3/16	1/4	5/16	3/8	7/16	1/2	5/8	3/4	7/8	1	.062	.630	.551	.496-.504	.512-.528
	3/8-24	.709	3/16	1/4	5/16	3/8	7/16	1/2	5/8	3/4	7/8	1	.062	.630	.551	.496-.504	.512-.528
	1/2	.866	3/16	1/4	5/16	3/8	7/16	1/2	5/8	3/4	7/8	1	.062	.709	.630	.575-.583	.591-.606

STANDARD MATERIAL: BRASS (B)
Other materials and lengths possible on quotation.

Specifying an Insert & Stud

Boss Design Specification

Hole Preparation

Hole diameter will vary with the type of plastic material used – hard plastics will require larger holes than softer plastics etc. For this reason, the data table shows the hole size ranges recommended for thermoplastics and thermosetting plastics. Exact hole size is best determined by pre-production trials – please consult the P.S.M Technology Centre. It is recommended that molded holes are used. 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. Tapers on molded holes should be 1° inclusive.

Type of Loading

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

Installation

The insert is installed using traditional tapping principles. Installation can be carried out using a hand tool (for low volumes), a tapping head attachment for a pillar drill, a standard tapping machine or fully automatic installation equipment.

Wall Thickness

This must be evaluated by pre-production tests in conjunction with the PSM Technology Centre – contact your local sales office for advice.

Performance Data

The complexity of materials and variations in service conditions make it impossible to detail fastener performance for specific applications. The charts below give a general guide and show the relative performance of the inserts in the range.

Enhance Your Assembly with Our Hardened Steel Screw Serts

Start browsing our products or request a quote today to find the ideal fastening solution for your application.

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.

Hardened Steel Screw-Serts

Advantages

Key Features