Threaded Inserts

A threaded insert is a small metal fitting, typically brass or steel, installed into a pre-drilled hole in wood to provide a durable, reusable machine-thread socket. Wood alone doesn't hold up well to repeated bolt removal and reinstallation — the fibers compress and tear a little more each time — so anywhere a project needs to be assembled and disassembled more than once (knock-down furniture, jigs, workbench accessories, removable hardware), a threaded insert is what actually holds up over years of use.

The common types

• Screw-in inserts — installed by turning the insert into a pre-drilled pilot hole, often with a hex key or a dedicated installation tool engaging an internal or external drive feature. E-Z Lok style inserts are a common example.
• Barrel nuts / cross dowels — a cylindrical nut set into a hole drilled perpendicular to a bolt hole, common in knock-down furniture hardware (bed frames, flat-pack cabinetry) where the bolt runs through one piece into the barrel nut seated in another.
• Threaded inserts for power tools (e.g., for T-track or jig hardware) — similar concept, sized and threaded to match specific hardware standards rather than general-purpose bolts.

Installation notes

Pilot hole size matters more than it might seem — too small and the insert is difficult to install without stripping the wood or cross-threading; too large and it won't grip. Manufacturers specify the correct pilot diameter for each insert size, and it's worth following that spec rather than guessing. Installing into end grain generally holds less securely than installing into face or edge grain, since the insert's threads are gripping fibers running parallel to the insert rather than across it.

Where they're worth the extra step

Workbench accessories and jigs that get bolted and unbolted regularly, knock-down furniture meant to be disassembled for moving, and any hardware mounting point that will see repeated stress or adjustment over the life of the piece. For a permanent joint that's assembled once and never touched again, a threaded insert is usually unnecessary complexity.