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Threaded Inserts · Trade series (self-tapping insert) · Application guide

What Are Self-Tapping Threaded Inserts Used For?

Typical applications, the industries that specify self-tapping threaded inserts, and how to choose the right size, material and finish for the joint.

Self-Tapping Threaded Inserts are used for putting a strong steel thread into aluminium, cast iron or timber, and repairing a stripped hole to its original size. They are manufactured to Trade series (self-tapping insert), and selection is driven by the thread size, the fit and tolerance the assembly requires, and the service environment.

Primary duty
Putting a strong steel thread into aluminium, cast iron or timber, and repairing a stripped hole to its original size
Governing standard
Trade series (self-tapping insert)
Thread size range
M3 to M10
Category
Threaded Inserts

Application notes are general engineering guidance. Verify the property class and any approval requirement against your own design calculation.

What Are Self-Tapping Threaded Inserts Used For? application image

Application guide for Self-Tapping Threaded Inserts to Trade series (self-tapping insert). The core duty of the type is putting a strong steel thread into aluminium, cast iron or timber, and repairing a stripped hole to its original size. The typical industries, the how-to-specify checklist, assembly practice and the exclusion cases are set out below. Stocked across roughly M3 to M10, they cover general to heavy-duty work.

Typical Applications for Self-Tapping Threaded Inserts

The most common settings where these are specified:

  • General machine building: fastening covers, brackets, motors and sub-assemblies on production equipment.
  • Maintenance & repair (MRO): a stocked size for servicing existing plant where the original fastener spec must be matched.
  • Fabrication & metalwork: bench and on-site assembly of steel frames, enclosures and weldments.
  • Aluminum & cast housings: durable steel threads in soft alloy that would otherwise strip.
  • Thread repair: restoring a stripped or cross-threaded hole to its original size.

How to Specify Self-Tapping Threaded Inserts for Your Application

  • Size: Match the nominal size to the mating thread or hole. This product spans M3–M10; check the full table below for the exact dimensions of each size.
  • Tap & length: Drill and tap to the specified STI size, and pick insert length (commonly 1.5×D or 2×D) for the load and parent material strength.
  • Environment: For damp, coastal or chemical exposure prefer A4/316 stainless or a suitable coating; indoors, plated steel or A2 is usually sufficient.
  • Standard: This product is supplied to Trade series (self-tapping insert). Quoting the standard on your order guarantees interchangeable dimensions between suppliers.

Installation & Assembly Practice

  • Drill and tap with the specified STI tap — a standard tap will not produce the correct thread for the insert.
  • Install to the specified depth (typically 0.25–0.5 mm below the surface) and remove the tang where the design requires it.

Common Selection Mistakes with Self-Tapping Threaded Inserts

  • Fitting an insert into strong steel that already holds a thread — added cost for no gain.
  • Skipping the tang removal, which then blocks the mating screw.

Where Self-Tapping Threaded Inserts Are Not the Right Choice

Not a fix for a hole that is already oversized beyond the STI tap range, and not needed in steel that already holds a thread well.

Custom manufacturing · Made to drawing

Need a self-tapping threaded inserts outside the standard range?

Thread size, body length, knurl or key form and installation method are all variable against the parent material. Made by tapping or knurling.

Minimum order from 2,000 pieces; samples within 7 days of drawing approval.

Custom threaded insert manufacturingSend a drawing

Technical Drawing

Customize the parameters below — every spec field is editable, and the drawing redraws to match the values you choose. Changing the size will snap the other fields to that size's standard values; you can then override any individual value.

Dimensioned line drawing of M3 Self-Tapping Threaded Inserts to Trade series (self-tapping insert). Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected.
Outer diameter (mm)
6.0
Length L (mm)
6.0
Hole in parent (mm)
6.0
Suitable parent material
Alloy, cast iron, plastic
Head form
Flush
Material
Case-hardened steel
Installation
Mandrel or driver
Sends the selected values to the quote form below.

Request a Quote

The form below follows the current technical drawing configuration. Change the drawing values above and the request details update automatically.

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Specification
Business Information

Dimensions & Specifications (Trade series (self-tapping insert))

Internal threadOuter diameter (mm)Length L (mm)Hole in parent (mm)Suitable parent materialHead formMaterialInstallation
M36.06.06.0Alloy, cast iron, plasticFlushCase-hardened steelMandrel or driver
M48.08.08.0Alloy, cast iron, plasticFlushCase-hardened steelMandrel or driver
M59.010.09.0Alloy, cast iron, plasticFlushCase-hardened steelMandrel or driver
M611.012.011.0Alloy, cast iron, plasticFlushCase-hardened steelMandrel or driver
M814.014.014.0Alloy, cast iron, timberFlushCase-hardened steelMandrel or driver
M1016.018.016.0Alloy, cast iron, timberFlushCase-hardened steelMandrel or driver

Video: What Are Self-Tapping Threaded Inserts Used For? in use

Video: What Are Self-Tapping Threaded Inserts Used For? in use

Third-party video, selected automatically for this topic. It is not produced by Engineering Hardware and is not a specification source — use the tables on this page for dimensional data.

Inside the plant

Manufactured in our own plant

This part is cold-formed, threaded, heat-treated and finished in-house. The stages below are where its class and finish are actually decided.

  1. Wire rod feeding into a cold heading machine
    01

    Cold heading

    Wire rod is drawn to size and cold-formed into blanks. Forming rather than cutting keeps the grain flow continuous around the head, which is where a bolt is most likely to fail.

    Head dimensions and under-head radius checked at set-up and per shift.

  2. Thread rolling machine producing bolt threads
    02

    Thread rolling

    Threads are rolled between hardened dies rather than cut. Rolled threads are stronger in fatigue than cut threads and hold pitch and flank angle far more consistently across a batch.

    Go / no-go ring gauges to ISO 965 tolerance class 6g.

  3. Baskets of bolts staged for heat treatment
    03

    Heat treatment

    Quench-and-temper brings carbon and alloy steel to the property class ordered — 8.8, 10.9 or 12.9 — with the furnace charge tracked so a finished lot can be traced back to it.

    Core hardness and tensile tested per lot to ISO 898-1.

  4. Zinc plated bolts in a treatment basket
    04

    Surface treatment

    Zinc, zinc-nickel, hot-dip galvanizing, black oxide, phosphate and Dacromet, selected against the service environment rather than against the price list.

    Coating thickness and neutral salt spray hours to ISO 9227.

Frequently Asked Questions

What are Self-Tapping Threaded Inserts used for?

Putting a strong steel thread into aluminium, cast iron or timber, and repairing a stripped hole to its original size. They are supplied to Trade series (self-tapping insert).

Which industries use Self-Tapping Threaded Inserts?

They are commonly specified in thread repair, plastics & composites and general machine building, among other sectors.

How do I choose the right size of Self-Tapping Threaded Inserts?

Match the nominal size to the mating thread or hole. This product is available from M3 to M10; the full dimension table on this page lists each size.

When should I use Self-Tapping Threaded Inserts instead of tapping directly?

Use them in soft alloys, plastics or thin sections where a cut thread would strip, or to repair a stripped hole. In strong steel that already holds a thread well, they are usually unnecessary.

Can I get a quote for Self-Tapping Threaded Inserts in the size and material I need?

Yes. Use the technical drawing and quote form on this page to set the size and options, then send the exact configuration to our team for pricing and lead time.