Brass Thread Inserts for Wood

What are brass thread inserts for wood? These are solid brass bushings with coarse external threads that cut into timber and a standard inch machine thread inside. Brass is the material of choice for wood inserts in visible and outdoor work for one specific reason: it contains no iron, so it cannot react with the tannins in oak, cedar, and walnut to produce the black staining that steel hardware causes around every fastener. AlbanyCountyFasteners.com stocks these in the E-Z Lok 400 series, from #4-40 through 3/8-24 in coarse and fine.

Brass

Size:

Why brass will not stain your workpiece

The reaction is worth understanding because it is avoidable and permanent. Oak, cedar, chestnut, and walnut all contain tannic acid. When iron meets tannin in the presence of moisture, even just humidity in the air, the result is iron tannate, a black compound that spreads into the wood fibers around the fastener. It is not a surface deposit you can sand off, and no finish covers it reliably. On a piece of white oak furniture, a ring of black around each insert is a defect the customer will notice immediately. Brass is copper and zinc with no iron content, so the reaction simply does not happen, which is why traditional furniture hardware has been brass for centuries.

Why choose brass wood inserts

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
Traditional material for fine furniture hardware

Inch sizes stocked

Coarse including #4-40, #6-32, #8-32, #10-24, 1/4-20, and 5/16-18
Fine including #10-32, 1/4-28, 5/16-24, and 3/8-24
Lengths from 0.375 inch on the smaller sizes up to 0.625 inch on 5/16 and 3/8
Order by the machine thread you need on the inside

Common applications

White oak, red oak, and cedar furniture where staining would show
Outdoor and garden furniture exposed to weather
Boat interiors, marine trim, and dock furniture
Fine cabinetmaking with visible joinery
Instrument builds, speaker cabinets, and acoustic work
Antique restoration where brass hardware is period correct

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

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Brass Wood Insert FAQs

Which woods stain from steel hardware?

Oak is the worst offender, along with cedar, chestnut, walnut, and mahogany. All are high in tannins. Pine, maple, and poplar are much less prone, so steel inserts are usually safe there if corrosion is not a concern.

What pilot hole size do brass inserts need?

Specified per insert size, and it matters more with brass than steel because a brass insert will deform before it forces its way into an undersized hole. Test in scrap of the same species first.

How are these driven?

The 400 series uses a slot in the top, driven with a flat blade or a purpose made driver. Start by hand to get it entering straight, then apply steady even pressure. Avoid impact driving, which deforms the slot.

Are brass inserts strong enough for furniture?

Yes for normal furniture loads. Pull-out strength depends on the wood and thread engagement rather than the insert material. Where brass gives ground is installation torque and repeated heavy loading on the internal thread.

Will brass tarnish?

It develops a patina over time, darkening from bright yellow toward brown. On furniture this is usually considered desirable, and it ages alongside the wood rather than corroding. It can be polished back if a bright finish is wanted.

Can I use these in plywood or MDF?

Yes, both hold inserts well. In MDF particularly an insert is far superior to a wood screw, which strips almost immediately on reassembly. Follow the specified pilot size, since engineered panels are less forgiving than solid timber.