How to build and reinforce thin wooden frames

the black square frames of the wall mounted bookshelves were painted with black matte paint

Building frames out of very thin profiles requires a secure reinforcement of the corners because the gluing surface is very small. We had to fix this problem in a previous project: our small floating bookshelves with a “check box” design.

We really wanted to replace the black tape (used for the project we discovered on Pinterest) with a wooden frame, so we could paint it with matte black paint. We decided to build them out of as thin as possible oak boards to be sure the frames won’t be a problem when arranging the books on the shelves. That’s how we got to use 8 mm thick pieces. For such a thickness, we had to find a solution to reinforce the frames, so they wouldn’t break when installed on the wall.

The whole building and strengthening process is part of a video you can watch on our YouTube channel:

How to build and reinforce thin wood frames

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Making the simple thin wooden frame

Building wooden frames is a very easy process. We usually start our projects with unedged timber. We plane them until we get a squared board with all the faces straightened. In this project, because we needed very small boards, we started from a few scrap pieces from older projects. We cut them with the bandsaw to a thickness of 1.5 cm and a width of 2.5 cm. We kept a margin large enough to be able to straighten all the faces.

We planed them with the thicknesser machine until we got the needed thickness of 0.8 cm and the width of 2 cm.

I planed some oak wood strips to build the square frames for the "check box" design of our small floating book shelves — Planing the oak strips for the frames of our “check box” design of floating book shelves

We set the 45-degree angle of the sliding circular saw. Then we cut one end of the boards. We cut two profiles at the same time. Why? To be sure that the boards that will be fitted face to face to form a frame would have exactly the same length. We turned the two boards, without moving them from each other, and we cut the second end at 45 degrees.

We did the same thing with the other thin boards. To make sure that the frame will close perfectly at the corners (that means the cutting angle of 45 degrees is correct), we matched the planks and checked the 90 degrees angle. If the angles were not 90 degrees, we would make small adjustments to the angle of the blade and then we would redo the cuts.

cutting the thin oak strips at 45 degrees to build square frames for the check box design of the floating book shelves — Cutting the 8 mm oak wood strips at 45 degrees needed for the square frames

We put a strip of painter tape (as narrow as possible) and we placed four thin strips inline, aligning them on one side. Then we applied the adhesive on the cut ends and closed them nicely forming the frame. The tape kept them in the right position and also tightened them at the corners (it didn’t allow them to move until the adhesive dried).

we glue up the square wooden frames needed for the small floating book shelves — Gluing up the square frames needed for our “check box” design

These are the thin square frames we needed for our project. Without reinforcing them, the corner joints would certainly not have been strong enough.

these are the frames that I will use to build the wall floating shelves — The wooden frames used for our creative floating shelves

Reinforcing the thin frames

The next step was to strengthen the corners, so we picked the simplest and fastest solution. Routing the corners and gluing narrow strips in the slots.

For this, we used a T-type slot cutting router bit (3.17 mm high, 10.17 mm diameter) that we found in our workshop (we don’t use it often, but sometimes it is very useful).

this is the T shape slotting cutter router bit I used to route the corners of the square frames to reinforced them with a thin oak wood strips — The T shape slotting cutter router bit

We cut a 3.17 mm thick oak strip (the height of the router bit). We wanted to glue small pieces cut from this strip into the routed slots of the frames.

that was the 3,17 mm oak wood strip I used to reinforce the corners of the wooden thin frames — The 3,17 mm oak wood strip

We used a piece of plywood as a guide for routing the slots. We secured it with clamps, to make sure it didn’t move while routing the slots.

I used a plywood strip to be able to route the corners of the wooden frame to reinforced them with a thin oak wood strip — Using a plywood strip to route the corners of the frame

We set the routing height so that we could get the slot in the middle of the corner. In this way, the routed slot would have had the walls thick enough and resistant to be reinforced: (8 mm thickness of the frame – 3.17 mm width of the cutter router bit): 2 mm

this is a slot routed with the T type slotting cutter router bit — The routed slots with the T type slotting cutter router bit

We glued the small pieces of wood, and after the glue dried, we cut the excess on the bandsaw.

I cut the excess using the bandsaw — Cutting the wood excess

We sanded the outside edges of the frames using the belt sander secured to the work table.

I sanded the thin wooden frames using the band sander with 120 grit sandpaper — Sanding the thin oak wood frames with the belt sander

We sanded the faces with the orbital sander with 120 grit sandpaper, and we rounded the sharp edges by hand.

i sanded the faces of the thin square frames with the orbital sander using 120 grit sandpaper — Sanding the faces of the square frames

At the end we applied two coats of matte black paint RAL 9011, sanding the surfaces with 320 grit sandpaper after the first coat dried. This is the way the thin oak frames looks after painting them:

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November 29, 2023

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