How To Glue Wood for Extra Thickness: Step-by-Step Guide

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Face gluing is a woodworking technique used to create thicker lumber from thinner boards.

It’s a process that requires attention to detail, as the strength of the glued joint is crucial for the structural integrity of the final piece.

Selecting the Right Type of Wood

  • Choose woods that are compatible in terms of hardness and grain structure to ensure a strong bond.
  • Avoid oily or resinous woods, as they can interfere with the glue’s ability to adhere properly.

Preparing the Wood Surface

  1. Measure and cut the wood pieces to the required dimensions.
  2. Inspect the surfaces for any defects, dirt, or grease, and clean them thoroughly.
  3. Sand the surfaces that will be glued together to create a smooth, flat area for better adhesion.
  4. Ensure that all edges are square and straight to avoid gaps when joined.

Choosing the Right Glue

  • PVA Glue: Ideal for indoor projects, offering a strong bond with a reasonable drying time.
  • Epoxy Resin: Suitable for both indoor and outdoor use, it provides waterproofing and fills gaps.
  • Polyurethane Glue: Strong and waterproof, it’s versatile for varying wood moisture levels.

Step-by-Step Instructions on Face Gluing Boards for Added Thickness

  1. Lay out the wood pieces on a flat surface to ensure proper alignment during the gluing process.
  2. Apply moderate glue to one surface of each piece of wood. If using a glue that requires mixing, like epoxy, mix according to the manufacturer’s instructions before application.
  3. Use a glue spreader or a brush to spread the glue across the entire surface, ensuring coverage from edge to edge.
  4. Align the wood pieces and press them together gently to ensure the glue makes contact across the surfaces.

Clamping Wood Pieces Together

  1. Arrange the clamps so that they are evenly spaced along the length of the wood pieces to apply consistent pressure.
  2. Use cauls, which are thick pieces of wood, to distribute the clamping pressure evenly across the surface and prevent indentations.
  3. Tighten the clamps until a thin bead of glue squeezes out along the joint line, indicating adequate pressure.
  4. Check the alignment of the wood pieces after clamping to ensure they haven’t shifted.

Curing Time and Conditions for A Strong Bond

  • Follow the glue manufacturer’s recommended curing time to ensure the strongest bond, typically 24 hours but may vary.
  • Avoid stressing the joint or moving the clamped pieces during this time to prevent weakening the bond.
  • Cure the glued pieces in a stable environment with controlled temperature and humidity to prevent the wood from warping or the glue from failing.

Frequently Asked Questions About Face Gluing

Face gluing can be a tricky and sometimes confusing process. Below we have laid out some common questions.

Is wood grain important in face gluing?

Yes, especially for aesthetic projects. Bookmatching the grain by folding cut pieces together can create a pleasing, symmetrical appearance at the glue joint.

Do I need to increase the thickness of my wood for strength?

Not always. For example, a ¾” thick furniture top is often sufficient in strength. Many cabinet and furniture makers apply a thicker edge to give the illusion of a thicker top, which saves on costs and wood resources.

Is it possible to glue plywood layers face to face?

Yes, plywood can be glued face to face using the standard method of applying glue, clamping the layers, and allowing adequate time for the glue to cure.

As you will see in the video, the ply orientation and direction also come into play when using plywood.

Can I glue two 2x4s together to form a 4×4?

Yes, you can glue two 2x4s together to create a 4×4. The basic steps of gluing, clamping, and curing apply. Depending on your project’s requirements, you may not need every step in detail. This method can also be more cost-effective than buying a 4×4.

Is it possible to face glue boards that are bowed?

Yes, but with caution. While you can face glue bowed boards using strong clamping, it’s better to remove the bow by planing first. Plane the bowed side to level it out, then plane the opposite side. This ensures a flat surface for a more stable glued joint.

Will glue squeeze-out stain the wood at the joints? How can I prevent this?

Glue squeeze-out can sometimes leave a mark, especially on woods with open grains. It’s best to wipe off any excess glue during clamping, and plan on sanding it off after it dries. For some glues, like PVA, you can use a damp cloth to wipe away the excess before it sets.

What if the glued-up board shows gaps or isn’t perfectly flat?

If there are gaps or the surface isn’t flat, it may be necessary to plane or sand the board after the glue has cured. Ensuring the surfaces are flat and clean before gluing can help minimize this issue.

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