How to cut and assemble picture mouldings with professional precision

Practical guide to cutting and assembling picture mouldings with professional precision

When it comes to manufacturing frames that stand out for their flawless finish, mastering the techniques of cutting mouldings and assembling mouldings is essential. In this guide, specifically aimed at professional workshops, we review step by step everything required: from selecting the appropriate machinery to the details of corner sealing and finish sanding. In addition, we include practical recommendations based on the experience of manufacturers specialising in picture mouldings.

Initial preparation: moulding selection and sizing

Before starting to cut or assemble, the first step is to correctly choose the picture mouldings to be used. At Intermol, there are multiple collections and references in wood, aluminium or composite materials, with finishes ranging from classic to contemporary. This allows the profile to be adapted to the style of the artwork, the frame thickness and the overall format.

Once the moulding has been selected, the artwork or canvas must be measured accurately, taking into account whether it will include glass, a mount or a backing board. It is advisable to add a few extra millimetres to facilitate fitting without creating tension. For example, if the artwork measures 50 × 70 cm and the frame uses a moulding 2 cm wide on each side, the lengths must be calculated by adding those widths and the allowance for the rebate. Preparing a preliminary layout helps to verify measurements and avoid mistakes.

Types of mitre saws for cutting mouldings

The moulding cutting stage makes the difference between a professional result and an amateur one. In a specialised workshop, two main types of machines are used: cutting machines and joining machines.

To achieve accurate cuts, it is recommended to:

• Use an adjustable mitre saw set to 45°, ideal for mitre cuts that allow precise joints.
• Ensure the blade is sharp and of high quality, especially when working with decorative or profiled mouldings.
• Keep the piece firmly secured to prevent movement or chipping.
• If the moulding is metallic or has a special finish, use specific blades to avoid burrs.
• Always carry out a test cut on an offcut before cutting in series, checking both angle and length.

The quality of the machinery directly influences cutting accuracy and, therefore, the fit of the frame corners.

Cutting technique: angles, marking and preparation

Cutting mouldings accurately requires method and discipline. The most effective steps are as follows:

First, mark the moulding with the exact measurements, including the rebate allowance. Then make the first cut at 45°, ensuring that the piece is straight and properly supported. The second piece must be cut in the opposite direction to achieve a 90° angle at the joint.

It is important to dry-fit each cut before assembly, checking that the corners meet without gaps and that the decorative surface remains intact. For mouldings with complex profiles, it may be necessary to adjust the edges with a fine file or fine sandpaper to achieve perfect contact between pieces.

Assembling mouldings: joining and fixing techniques

Once the pieces have been cut accurately, it is time to assemble mouldings. To achieve a solid, perfectly square frame, several key steps should be followed.

Applying wood glue to the joint areas provides rigidity and durability. The amount should be controlled, avoiding excess that could seep out of the joint. It is then advisable to hold the pieces in place using a square or jig to maintain exact 90° angles while the adhesive dries.

For large frames, it is recommended to reinforce the joints with V-nails, pins or concealed screws. Professional joining machines are particularly useful in this process, as they ensure uniform pressure and repeatable precision.

Once the pieces are fixed, the squareness should be checked by measuring the diagonals of the frame. If both diagonals match, the structure is perfectly aligned.

When the frame is dry, the corners should be sealed with filler or resin to eliminate micro-gaps. After the filler has dried, light sanding integrates the repair with the surface of the moulding.

Corner sealing and finish sanding

The finish is what gives the work its professional appearance. For this reason, sealing and sanding are essential stages.

First, a general sanding is carried out to remove irregularities, glue residue or imperfections from the cut. At this stage, the joints should be flush with the rest of the profile.

If any gaps are detected, they are filled with a filler as close as possible to the moulding colour. Once dry, the surface is sanded again with fine-grit paper to achieve an even finish.

Before applying varnishes or lacquers, it is essential to remove dust using a damp cloth or vacuum cleaner. A clean surface ensures proper adhesion of the finish and a smooth, even appearance.

Finally, the appropriate decorative finish is applied, whether varnish, wax, paint or lacquer, depending on the type of moulding selected. Natural wood mouldings generally look best with finishes that enhance the grain, while lacquered or metallic mouldings require finer sealing.

Final frame inspection

Once the frame is fully assembled and finished, it is time to carry out a final inspection.

Check that the dimensions are correct and that the artwork fits perfectly without play or pressure. The joints, profile alignment and uniformity of colour and sheen should also be inspected.

If the frame is intended for hanging, it is necessary to ensure that the hanging system is correctly centred and securely fixed. Even a slight misalignment can cause the picture to hang crooked.

For transport or storage, it is advisable to protect the corners with cardboard and wrap the frame with film or foam, especially if the mouldings have delicate finishes.

Additional advice for workshops

Workshops seeking to maintain consistent production quality should establish stable working routines. Keeping the mitre saw properly calibrated is essential, as even minimal deviation can ruin a frame. It is advisable to check angles regularly with a precision square and replace the cutting blade when it becomes dull.

Working in series is another efficient strategy: cutting all pieces before assembly allows better control of consistency and avoids measurement errors. Labelling each piece according to its position in the frame (top, bottom, left or right) speeds up the process and prevents confusion.

Quality control should be carried out systematically. Inspecting each frame before applying the finish saves time and materials. In addition, it is advisable to train staff in framing techniques, mitre cutting, sealing and finishing. Continuous training raises the workshop’s quality standard.

Finally, keeping the work area clean and free of debris directly contributes to accuracy. Dust and shavings can interfere with cutting and affect finishes, so cleanliness must be part of the daily process.

Carrying out professional cutting and assembly work on picture mouldings involves combining technique, precision and experience. The correct choice of materials, the use of quality tools and the meticulous execution of each stage—from cutting to sealing and sanding—are determining factors in the final result.

A well-crafted frame not only protects and enhances the artwork, but also reflects the skill of the workshop. By following these guidelines and applying rigorous control at every stage of the process, it is possible to achieve picture mouldings with impeccable finishes, durability and perfect alignment, worthy of the highest standards of professional framing.