Joining

Joining

Definition: Joining is the process of assembling frame moulding sections at their corners to create a complete picture frame. Typically, corners are cut at 45° angles (mitered) to achieve a clean, continuous visual line. Joining involves the use of adhesives, fasteners, or mechanical reinforcements to ensure structural integrity and long-lasting stability.

Common Joining Methods

• Glue Only: Adhesive is applied to mitered corners, sometimes reinforced with clamps or jigs during curing. Suitable for lightweight frames or decorative pieces.
• Glue and Nails: Small finish nails or brads are used in conjunction with adhesive to reinforce joints and prevent separation over time.
• Dovetail-Key Miter: Mitered corners are routed to accept a dovetail-style plastic key or thumbnail biscuit, which draws the corners together for strength.
• Spline Joint: A thin strip of wood (spline) is inserted across the miter joint to increase alignment and durability.
• Unjoined: Rails that are cut but not yet assembled, used for pre-planning or customization before final joining.

Key Considerations

• Precision: Accurate miter cuts are essential to avoid gaps and misalignment.
• Reinforcement: Consider additional support such as splines, keys, or corner brackets for heavy frames.
• Material: The type of moulding-wood, MDF, metal, or composite-dictates the best joining method.
• Finish: Ensure joining methods do not damage or obscure decorative finishes, inlays, or embossing.
• Clamping: Proper clamping or jigs help maintain square corners while adhesives cure.

Best Practices

• Always verify that frame corners are perfectly square before applying glue or fasteners.
• Use a miter clamp or band clamp for consistent pressure along all corners.
• Reinforce larger or heavy frames with splines, dovetail keys, or mechanical hardware to maintain long-term stability.
• Check alignment with a square or corner jig before final fastening.

Related Terms

• Spline Joint
• Miter Joint
• Dovetail Key Miter
• Unjoined