Joining two boards end to end to increase their length can be accomplished using several different woodworking joint techniques, each offering varying degrees of strength and appearance.
To join two boards together end to end, you can use methods that create interlocking surfaces or reinforce a simple connection. One highly effective method involves using finger joints, which can be made with specialized cutters.
Common Methods for End-to-End Board Joints
Choosing the right joint depends on the required strength, desired appearance, and available tools. Here are several common methods:
- Finger Joint: Creates interlocking 'fingers' on the ends of the boards. This joint offers a large gluing surface area, resulting in exceptional strength.
- Using standard angled finger joint cutters provides a very strong joint.
- If the angles are correct, you can actually glue the boards without clamping.
- When the cutter is made right, the boards can simply be pressed together and the glue left to dry; they will not push themselves back apart.
- Scarf Joint: An angled cut is made on the ends of both boards, creating a long, overlapping surface area for gluing. This is a strong joint often used for lengthening structural timbers.
- Dowel Joint: Holes are drilled into the ends of both boards, and wooden dowels coated in glue are inserted into one board's holes, then the other board is pressed onto the protruding dowels.
- Biscuit Joint (or Plate Joiner Joint): Oval slots are cut into the ends of both boards using a biscuit joiner. Oval wooden 'biscuits' are inserted into the slots with glue, and the boards are clamped together. The biscuits swell slightly, creating a tight fit.
- Spline Joint: A groove (dado) is cut into the ends of both boards, and a separate strip of wood (the spline) is glued into the grooves to align and strengthen the joint.
- Butt Joint (Reinforced): A simple square cut on both ends. While the easiest to make, a plain butt joint is weak for end-to-end connections unless reinforced with plates, dowels, biscuits, or other fasteners.
Steps for Making a Finger Joint (General)
- Prepare the Ends: Ensure the ends of both boards are cut square initially.
- Set up the Cutter: Install the correct finger joint cutter in your router table or specialized machine. Adjust the height and fence according to the cutter's instructions and the thickness of your material.
- Cut the Fingers: Carefully pass the end of each board through the cutter to create the interlocking finger profile. Ensure consistent setup for both pieces so they fit together perfectly.
- Test Fit: Dry-fit the joint to ensure the fingers interlock snugly.
- Apply Glue: Apply woodworking glue to the finger surfaces of both boards.
- Join the Boards: Align the fingers and press the boards together. As noted with standard angled cutters, if the angles are correct, you may not need clamps; simply pressing them together may suffice as they won't push apart. For other finger joint types or added security, apply clamping pressure until the glue dries.
- Clean Up: Wipe away excess glue with a damp cloth.
- Allow to Cure: Let the glue dry completely according to the manufacturer's instructions before stressing the joint.
While other methods exist, the strength provided by a well-executed finger joint, especially using cutters designed for correct angles, offers significant advantages for joining boards end to end.
