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Threaded Inserts · Trade series (key-locking insert) · Application guide

What Are Key-Locking Threaded Inserts Used For?

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

Key-Locking Threaded Inserts are used for thread repair and reinforcement in high-vibration and safety-critical assemblies, locked into the parent metal by driven keys. They are manufactured to Trade series (key-locking insert), and selection is driven by the thread size, the fit and tolerance the assembly requires, and the service environment.

Primary duty
Thread repair and reinforcement in high-vibration and safety-critical assemblies, locked into the parent metal by driven keys
Governing standard
Trade series (key-locking insert)
Thread size range
M4 to M12
Category
Threaded Inserts

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

What Are Key-Locking Threaded Inserts Used For? application image

Application guide for Key-Locking Threaded Inserts to Trade series (key-locking insert). The core duty of the type is thread repair and reinforcement in high-vibration and safety-critical assemblies, locked into the parent metal by driven keys. The typical industries, the how-to-specify checklist, assembly practice and the exclusion cases are set out below. Stocked across roughly M4 to M12, they cover general to heavy-duty work.

Typical Applications for Key-Locking Threaded Inserts

The most common settings where these are specified:

  • Thread repair: restoring a stripped or cross-threaded hole to its original size.
  • Plastics & composites: reinforced, reusable threads in molded parts.
  • 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.

How to Specify Key-Locking Threaded Inserts for Your Application

  • Size: Match the nominal size to the mating thread or hole. This product spans M4–M12; 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 (key-locking 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 Key-Locking 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 Key-Locking 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 key-locking 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 M4 Key-Locking Threaded Inserts to Trade series (key-locking insert). Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected.
External thread
M8x1.0
Length L (mm)
8.0
Tapped hole required
M8x1.0
Keys
4
Locking method
Driven keys broach parent
Material
Carbon steel / 303 stainless
Typical use
High-vibration repair
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 (key-locking insert))

Internal threadExternal threadLength L (mm)Tapped hole requiredKeysLocking methodMaterialTypical use
M4M8x1.08.0M8x1.04Driven keys broach parentCarbon steel / 303 stainlessHigh-vibration repair
M5M10x1.2510.0M10x1.254Driven keys broach parentCarbon steel / 303 stainlessHigh-vibration repair
M6M12x1.2512.0M12x1.254Driven keys broach parentCarbon steel / 303 stainlessHigh-vibration repair
M8M14x1.2514.0M14x1.254Driven keys broach parentCarbon steel / 303 stainlessAerospace, motorsport
M10M16x1.516.0M16x1.54Driven keys broach parentCarbon steel / 303 stainlessAerospace, motorsport
M12M20x1.520.0M20x1.54Driven keys broach parentCarbon steel / 303 stainlessAerospace, motorsport

Video: What Are Key-Locking Threaded Inserts Used For? in use

Video: What Are Key-Locking 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 material should Key-Locking Threaded Inserts be for outdoor use?

For damp, coastal or chemical environments specify A4 (316) stainless or a suitably coated steel. For indoor or dry use, A2 (304) stainless or zinc-plated steel is normally adequate.

Are Key-Locking Threaded Inserts made to a recognized standard?

Yes — they are manufactured to Trade series (key-locking insert), so dimensions are interchangeable between suppliers when you quote the standard on your order.

What are Key-Locking Threaded Inserts used for?

Thread repair and reinforcement in high-vibration and safety-critical assemblies, locked into the parent metal by driven keys. They are supplied to Trade series (key-locking insert).

Which industries use Key-Locking Threaded Inserts?

They are commonly specified in fabrication & metalwork, aluminum & cast housings and thread repair, among other sectors.

Can I get a quote for Key-Locking 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.