Metric Brass Thread Inserts for Wood

What are metric brass wood inserts? These are solid brass bushings with coarse external threads that cut into timber and a standard metric machine thread inside. They bring together two requirements that often arrive on the same project: a metric thread to match imported hardware, and a non-ferrous material that will not stain tannin-rich timber. Brass contains no iron, so the black staining steel produces in oak and cedar simply does not occur. AlbanyCountyFasteners.com stocks the E-Z Lok 400 series in M3 through M8.

Metric Brass

Size:

When do you need a metric insert in wood?

Whenever the bolt going into it is metric, which covers more furniture work than the inch-dominated US market suggests. European cabinet fittings, imported knockdown hardware, and most contemporary connector bolt systems are M6 or M8 throughout. Instrument hardware is frequently metric. So is a great deal of imported furniture arriving for repair, where the customer still has the original bolt and expects it to go back in. Fitting an inch insert in any of those cases creates a joint that accepts none of the hardware built for it, which usually surfaces months later when someone needs to take the piece apart. Match the insert to the fastener that will actually be used.

Why choose metric brass wood inserts

Accepts standard metric bolts and imported furniture hardware
No iron content, so no black tannin staining in oak, cedar, or walnut
Corrosion resistant for humid interiors, outdoor furniture, and marine work
Warm tone that blends with most timbers on visible joints
Softer than steel, reducing splitting risk in marginal pilot holes

Metric sizes stocked

M3 and M4 in 0.375 inch length
M5 in 0.500 inch length
M6 in 0.500 inch length
M8 in 0.625 inch length
Order by the metric thread you need on the inside, then check the pilot hole specification

Common applications

Imported furniture repair where the original bolt is metric
European cabinet systems and connector bolt hardware
Oak and cedar furniture where steel would stain
Outdoor and garden furniture using metric fittings
Instrument builds and speaker cabinets with metric mounting hardware
Boat interiors and marine woodwork

For inch threads, see our brass thread inserts for wood. Where higher installation torque is needed in interior work, metric hex drive inserts in zinc alloy steel drive harder.

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Metric Brass Wood Insert FAQs

Which metric size do I need?

Match the bolt, not the joint size. M6 covers most connector bolt and cam fitting systems in flat pack furniture. M8 appears on heavier joints like bed rails and table bases. M3 and M4 suit small hardware, instrument fittings, and light assemblies.

What pilot hole do metric brass inserts need?

Specified per insert size and different from the inch equivalents. Brass is less forgiving than steel of an undersized hole, since it will deform rather than force its way in, so test in scrap of the same species before drilling the workpiece.

Can I use an inch bolt in a metric insert?

No. The internal thread is metric and accepts only metric hardware. If your fasteners are inch, order the inch version instead.

How do I drive these without damaging the slot?

Start by hand so the insert enters straight, then apply steady even pressure with a well fitting flat blade or a purpose made driver. Brass deforms more readily than steel, so avoid impact driving and back off if resistance climbs sharply.

Will these stain oak?

No. The staining reaction requires iron, which reacts with tannins in the wood to form black iron tannate. Brass is copper and zinc with no iron content, so the reaction does not occur.

What if my metric size is not listed?

Contact us with the thread size and the depth available in your workpiece. We can advise on availability for sizes outside the stocked range, or on whether an inch insert would serve if the hardware is flexible.