Making Nice with Knots
Know your knot anatomy
A knot is nothing more than the base of a tree branch where it intersected the tree trunk, interrupting the otherwise straight grain pattern, causing it to flow around it. Knots can be grouped into two basic categories, but you'll see them in all stages between the two.
Tight knots appear as dark, dense circular or oval spots with irregular grain. The wood remains unbroken between the tree trunk and the embedded branch. They represent a relatively weaker spot in the wood, and, over time, could split as the knot moves at a different rate than the surrounding wood.
Loose knots are generally darker and have shrunk away and detached from the surrounding wood during the growing process. They contain visible cracks or gaps and are often surrounded by a thin layer of scar tissue called callus. Some are loose enough to be removed by hand and require extra precautions when cutting.
Keep your knots where they belong
Before you can machine them, use 5-minute epoxy to lock loose and loosening knots into place and fill any gaps and voids. When the epoxy cures, you can saw, joint, or plane the wood without fear of knocking the knot out, or worse, sending it flying across the shop or damaging your machinery.
Be sure to choose clear-drying epoxy so the knot retains its natural look. (The epoxy will appear transparent in its applicator.) White-drying, opaque, or colored epoxy often highlights the knot, emphasizing it with an unnatural ring.
Here are two approaches for locking in loosening and loose knots.
Small gaps in loosening knots may require injecting epoxy with a glue syringe in order to lock in knots.
To draw the epoxy into the gaps, use a shop vacuum. Protect the hose by rubber-banding a paper towel over the end.
After removing the knot, clean any loose bark and debris from the knothole and the knot using a brass wire brush.
Mix up a small amount of epoxy and spread it liberally on the outside of the knot and reposition it in the board.
Spread additional epoxy to fill any remaining voids. After the epoxy cures fully, machine as you would any other board.
Show off your knots
Knots make an acceptable feature in many projects, especially those made of pine and cedar. In fact country-style or rustic furniture almost requires them. Rather than letting knots dot the project will-nilly, be deliberate about their placement as you would any other wood figure. Take a look at some of our favorite examples: