How to Install Threaded Inserts in Plywood Without Splitting
Threaded inserts are a handy way to add durable machine-thread connections to woodworking projects. They're especially useful for knock-down furniture, shop-made jigs, and accessories that need to be assembled and taken apart repeatedly.
But installing threaded inserts into the edge of plywood can be tricky. The hole needs to be drilled straight, and driving the insert into the layered edge can cause the plywood to split or separate.
Fortunately, two simple shop-made guides and a handscrew clamp can make the job much easier. These tips help keep the hole and insert aligned while supporting the plywood during installation.
Use a Drill Guide to Keep the Hole Straight
Drilling into the narrow edge of plywood requires accuracy. If the drill bit wanders or enters at an angle, the threaded insert may end up crooked or break through the face of the panel.
A simple drill guide helps keep the bit perpendicular to the plywood edge.
Make a Shop-Made Drill Guide
The guide consists of a small plywood cleat glued to a hardboard fence.
Start by drilling a through hole in the plywood cleat using a drill press. This ensures the hole is square to the cleat's face.
Then glue the cleat to the hardboard fence, positioning it so the guide hole aligns with the desired location on the plywood edge.
To use the guide, clamp it securely to the workpiece. The hardboard fence registers against the plywood face, while the hole in the cleat guides the drill bit straight into the edge.
Wrap a piece of tape around the drill bit to mark the required drilling depth. This provides a simple visual reference and helps prevent drilling too deeply.
Prevent Plywood Splitting With a Handscrew Clamp
Once the hole is drilled, the next challenge is installing the threaded insert without damaging the plywood.
As the insert threads bite into the material, they exert outward pressure against the surrounding wood. Along a plywood edge, this pressure can cause the layers to separate or split.
The solution is to support the plywood faces while driving the insert into place.
Clamp the Plywood Before Installing the Insert
Position a wooden handscrew clamp over the plywood edge, with the jaws pressing against the faces of the panel near the insert hole.
The clamp helps resist the outward pressure created as the insert is driven into the plywood.
An ordinary clamp with suitable pads can also be used, but the broad wooden jaws of a handscrew provide convenient support on both sides.
Tighten the clamp enough to hold the plywood layers together without crushing the material.
Use an Installation Guide to Keep the Insert Aligned
Keeping the threaded insert straight is just as important as drilling an accurate hole.
A simple installation guide prevents the insert from tipping as it begins threading into the plywood.
The guide consists of two pieces of plywood with an aligned hole sized to fit the installation bolt.
Thread a nut and the insert onto the bolt, then pass the bolt through the guide. The guide keeps the bolt aligned with the drilled hole while the insert is installed.
With the plywood edge supported by the handscrew, use a socket wrench to turn the bolt and drive the insert into place.
Work slowly and keep the guide seated squarely against the workpiece. Stop if the insert begins to bind or the plywood shows signs of splitting.
Once the insert is seated, remove the installation bolt.
Get Better Results With Threaded Inserts in Plywood
Installing threaded inserts into plywood edges doesn't have to be frustrating. The key is controlling alignment and supporting the plywood throughout the process.
A shop-made drill guide keeps the hole straight, while a simple installation guide helps the insert enter squarely. Adding a handscrew clamp around the plywood edge helps prevent splitting as the insert is tightened.
Before installing inserts in a finished project, test the technique on a scrap of the same plywood. Use the hole size recommended for your specific insert and make sure there's enough material around the hole to support it.
With these simple techniques, you can create reliable threaded connections for shop-made jigs, removable accessories, and other woodworking projects.
Handscrew Clamps: One of the Most Versatile Woodworking Clamps
A wooden handscrew does more than hold parts together during glueups. Its adjustable jaws make it useful for supporting delicate workpieces, holding irregular shapes, and solving tricky workholding problems.
Discover More Clever Uses for Handscrew Clamps ➜ Handscrew Clamps: 4 Clever Uses for Woodworking
