Timber Insert Nut

Threaded inserts for wood: what a timber insert nut does

A timber insert nut is a short zinc alloy sleeve with a thread on the outside, a metric machine thread inside, a flange at the top and a hex socket in the flange. You screw it into a pre-drilled hole in the timber with a hex key. The outside thread holds it in the wood; the inside thread takes a standard metric bolt or machine screw.

The point is a thread you can undo and do up again: the bolt wears against the zinc alloy thread, not the timber. That is why they are used for knock-down furniture and cabinet joints, removable timber fixings, and jigs, workbenches and fixtures in timber.

Hobson publishes no pull-out or load rating for these inserts. They are for furniture, joinery and fittings; for anything structural, or anything that holds people or loads, use a rated fixing that an engineer or designer specifies.

Timber insert nut sizes

Choose the insert by the bolt or screw that goes into it: an M6 insert takes an M6 bolt. The thread is in the lower part of the insert, below the hex socket, so for full engagement the bolt should reach the bottom of the insert: bolt length = the thickness of the part you are fixing + the insert's overall length. For example, fixing an 18mm panel to an M8 x 15 insert takes an M8 bolt about 33mm long (18 + 15), which engages all 9mm of thread. Go longer only if the pilot hole is drilled deeper than the insert. Select a row to open that size in the selector.

How to fit threaded inserts for wood

1. Mark the position and drill a straight pilot hole, square to the face, at least as deep as the insert is long. Hobson publishes no pilot hole sizes for these flanged inserts (its 7.5mm and 10mm figures are for the non-flanged M6 and M8 inserts on our timber fittings page), so drill a test hole in an offcut of the same timber first: the insert should cut its own thread and hold firmly without splitting the wood.
2. Screw the insert in with a hex key of the size in the table (4mm for M4 up to 10mm for M10), keeping it square, until the flange sits on the timber.
3. Stop when the flange seats. Turning further can strip the thread the insert has cut in the wood.
4. Bolt the part on with a metric bolt or machine screw of the same thread size.

Zinc yellow finish: where these inserts suit

These inserts are zinc alloy with a zinc yellow passivate finish. Hobson rates zinc yellow as low corrosion resistance on its finish comparison, for low-corrosion environments or temporary fixing. That suits indoor furniture, cabinets, shop fittings and jigs.

Hobson's corrosion guide calls for stainless steel or hot dip galvanising for fixings exposed to the weather, so these are not for outdoor furniture, decks or anything left out in the rain. For fixing into timber outdoors, the 316 stainless countersunk timber insert is on its own page. Hobson lists it for fixing wire rope balustrade into timber but publishes no pull-out rating for it either; a balustrade needs the designer's specification.

Timber insert nut, tee nut or barrel nut?

• •Timber insert nut: screws into a drilled hole from the face you are working on, leaving a flanged, reusable metric thread.
• •Non-flanged timber insert nuts (M6 x 13 and M8 x 15, zinc yellow) are on our timber fittings page. They are the only inserts Hobson gives pilot holes for: 7.5mm for the M6 and 10mm for the M8, with no pre-drilling needed in softwood.
• •Tee nut: four prongs that set into timber, composite or particle board to leave a flush or recessed female thread.
• •Barrel nut and furniture connector bolt: a pair for joining furniture panels and frames.
• •Rivet nut: for a thread in sheet metal and thin sections, not timber.

Threaded inserts for wood in Adelaide

Allmat supplies timber insert nuts, tee nuts, barrel nuts and socket screws to cabinet makers, joiners, shopfitters, builders and trade across Adelaide and South Australia. Add them to a quote with the rest of your list and we will price the lot.

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