Metric 303 Stainless Steel Thread Inserts for Metal

What are metric 303 stainless thread inserts? These are solid bushing inserts in 303 stainless, sized to metric threads. Each is machined with an external thread that grips a tapped hole and an internal metric thread that accepts standard metric hardware. Because the body is a rigid sleeve rather than a wound coil, it carries substantially more pull-out and torque-out load and survives repeated disassembly. Some sizes are made as conversion inserts, taking an inch external thread and providing a metric internal one. AlbanyCountyFasteners.com stocks M5, M6, M8, and M10.

Metric 303 Stainless Steel

Size:

When do you need a metric to inch conversion insert?

More often than you would expect on mixed equipment. A machine built to metric drawings that has been repaired with inch hardware, or an inch assembly that needs to accept a metric component, leaves you with a hole in one system and a fastener in the other. A conversion insert resolves it in one part: the external thread matches what is already tapped in the parent material, and the internal thread gives you the system you actually need. That is cleaner than drilling out and retapping the whole boss, and it avoids the situation where an assembly ends up with a mix of thread systems nobody has documented.

Why choose metric 303 stainless solid inserts

Provides a standard metric internal thread that accepts factory hardware
Higher pull-out and torque-out strength than metric wire coil inserts
Available in conversion sizes that bridge inch and metric systems
Clean machined threads from free-machining 303 stainless
Withstands repeated assembly and disassembly cycles

Metric sizes stocked

M5-0.8, M6-1.0, and M8-1.25 in standard metric inserts
M8-1.25 and M10-1.25 available as conversion inserts with inch external threads
Check both the external and internal thread specification before ordering
Contact us for metric sizes outside the listed range

Common applications

Imported machinery and equipment built to metric drawings
Metric engine, gearbox, and housing repair
Mixed inch and metric assemblies needing a thread system bridge
High load metric joints in aluminum and soft metals
Metric tooling, jigs, and fixtures serviced regularly
Motorcycle and imported vehicle repair

For inch threads, see our 303 stainless thread inserts. Where the boss is too thin for a solid insert, metric Helicoil wire inserts remove less material.

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Metric Thread Insert FAQs

What is a conversion insert?

An insert whose external and internal threads belong to different systems, for example an inch external thread with a metric internal thread. It lets you install metric hardware into a hole tapped in inch, or the reverse, without retapping the parent material.

Do I need a metric tap?

It depends on the insert's external thread. A standard metric insert taps with a metric tap sized to its external thread. A conversion insert with an inch external thread needs an inch tap. Always check the external thread specification, not the internal one.

Are these stronger than metric wire inserts?

In pull-out and torque-out, yes, because a solid sleeve grips through a positive external thread rather than spring tension. They do require a larger hole, so confirm the boss has enough material before choosing solid over wire.

Will standard metric bolts fit?

Yes. The internal thread is a standard metric thread in the size listed, so factory metric hardware threads in normally once the insert is installed.

Can I use these in aluminum?

Yes, and that is a primary use. Aluminum threads strip readily under repeated assembly, and a stainless insert gives a hardened thread surface that lasts far longer than the aluminum did.

What if my metric size is not listed?

Contact us with the thread size, the hole depth, and whether you need a standard or conversion insert. We can advise on availability for sizes outside the stocked range.