Installing Cam and Dowel Connectors: Step-by-Step Guide for 15 mm Cam Holes and Connecting Bolts

A cam lock connector is a two-part furniture fitting consisting of a 15 mm diameter cylindrical housing and a connecting bolt, used to join board materials firmly at a 90-degree angle.

The construction of modern cabinet carcasses relies heavily on demountable connecting fittings. For joiners and fitters, the professional installation of these cabinet connectors is an essential core skill. Unlike glued wooden dowels, the system of cam lock casing and connecting bolt enables non-destructive disassembly. This is particularly relevant for large-scale furniture units. When building substantial constructions, such as a two-person wardrobe, the stability of the corner joints is vital for the load-bearing capacity of the entire frame.

In living areas, such as during the assembly of a TV sideboard or a low TV unit, these fittings offer the technical advantage of completely concealed installation. No visible screw heads remain on the outer faces of the cabinet side panels. Even when dynamic loads act upon the carcass later — for instance, if a gas strut for heavy flaps is fitted to the front — the corner joint must permanently withstand the resulting leverage forces.

The following guide details the precise installation of the 15 mm cam hole and the insertion of the corresponding bolts in chipboard or MDF.

Required Tools and Materials

Accurate tools are indispensable for cutting and drilling connecting fittings cleanly. Millimetre-level deviations inevitably lead to misaligned joints or inadequate clamping force.

• Forstner bit (Ø 15 mm) with centre point
• Wood drill bits (Ø 8 mm and Ø 5 mm)
• Depth stop (drill stop) for all drill bits
• Cordless drill or pillar drill
• Try square and vernier calliper
• Marking gauge or drilling template for the System 32
• Screwdriver with PZ drive (usually Pozidriv PZ2)
• Cam lock casings (15 mm) and matching connecting bolts

Much like routing a large recess for a desk cable grommet, the 15 mm hole requires steady tool guidance to prevent tear-out on melamine coatings.

The Dimension System: Preparation and Geometry

Before positioning the drill bit, the geometry of the fitting must be understood. The system is based on a standardised drilling pattern. The distance from the front edge of the shelf to the centre of the 15 mm hole is known as the backset drilling distance (B). In most standard cam lock connectors, this measurement is exactly 34 mm or 24 mm. In this guide, we use the common 34 mm dimension.

The board thickness of the material (usually 16 mm or 19 mm) dictates the depth of the cam hole as well as the position of the edge drilling. The edge hole must sit precisely in the centre of the board thickness (for a 16 mm board, this means at a height of 8 mm).

Step-by-Step Guide: Installing Cabinet Connectors

Step 1: Measuring and Marking Out

Accuracy during marking out determines whether the furniture edges will finish flush.

1. Lay the shelf flat on the workbench.
2. Mark the centre of the board thickness on the front edge (e.g. at 8 mm on a 16 mm board).
3. Transfer this centre line onto the face of the board.
4. Measure exactly 34 mm inward from the edge along the marked line using a marking gauge. This intersection is the centre point for the Forstner bit.

Step 2: Drilling the 15 mm Cam Hole

The cam lock casing must sit flush or slightly recessed in the board. If it sits proud, it will rub against the adjacent component.

1. Insert the 15 mm bit into the chuck and attach the depth stop.
2. Set the drilling depth. For a 16 mm board, the drilling depth is usually 12 mm to 12.5 mm. For a 19 mm board, it is 14 mm to 14.5 mm. Check the height of your specific cam lock casing with a vernier calliper.
3. Place the centre point precisely on the 34 mm mark.
4. Drill vertically into the board at high speed with light feed pressure. Clear all wood chips thoroughly from the hole.

Step 3: Edge Drilling for the Bolt Channel

The shaft of the bolt passes through this channel to reach the cam lock housing.

1. Switch to the 8 mm wood drill bit.
2. Position the drill bit on the edge face (precisely centred, e.g. at 8 mm height).
3. Drill horizontally into the board until you break through into the 15 mm cam hole. The channel must run strictly at a 90-degree angle to the edge, otherwise the bolt will jam.

Step 4: Drilling the Side Panel and Setting the Bolts

Now prepare the side panel (the mating part) into which the bolt is driven. Here, the shelf grid dimensions must be transferred to the side panel. In a kitchen, such as with a wall cabinet holding a wall unit dish drainer rack, connectors positioned at identical heights ensure perfect shelf alignment.

1. Mark the exact position on the side panel.
2. The required hole depends on the bolt type:

• Euro screw (direct thread): Drill a 5 mm hole. The depth depends on the thread length of the bolt (usually 11 mm to 15 mm).
• M6 thread with insert: Drill an 8 mm hole for a threaded insert or pronged tee nut.

1. Screw the bolt in vertically using a PZ screwdriver. The collar of the bolt must rest flush against the surface of the board.

Step 5: Assembly and Locking

This is the mechanical joining of the components. As the cam rotates, it pulls the head of the bolt towards itself, locking the panels tightly together without play.

1. Slide the shelf with its 8 mm edge drilling over the fitted bolt on the side panel. The head of the bolt must now be visible inside the 15 mm cam hole.
2. Insert the 15 mm cam lock housing into the recess. The open side (arrow marking) must point towards the edge and the bolt head.
3. Turn the housing clockwise using a manual screwdriver (approximately 180° to 210°). You will feel distinct resistance as the cam grips the bolt head and pulls the boards together. Do not overtighten with excessive force.

Common Mistakes and Technical Tips

Even with careful workmanship, tolerances can occur that compromise the stability of furniture components.

Step at the edges: If the edge of the shelf is not flush with the side panel, there is a measuring discrepancy. Usually, the 8 mm edge drilling was not made at an exact 90-degree angle, causing the bolt to push the shelf up or down. Using a dowelling jig or drilling template eliminates this angular error.

The cam fails to grip: If the housing spins freely without generating tension, the bolt head does not extend far enough into the 15 mm hole. This is usually caused by an excessive backset distance (e.g. 35 mm instead of 34 mm from the edge) or wood shavings inside the edge channel that prevent the shelf from sliding fully against the panel.

Surface breakthrough: If the 15 mm hole is drilled too deep, the centre point of the bit will push through the decorative veneer on the reverse side. In a 16 mm thick chipboard with a 12 mm drilling depth, only 4 mm of core material remains. A firmly set metal depth stop is essential here.

Incorrect torque: Cordless drills should never be used to tighten cam lock casings. Torque is difficult to control. If the internal rib of the cast housing shears off, the connector becomes useless and must be painstakingly removed with needle-nose pliers. Always tighten the fitting by hand.

FAQ: Frequently Asked Questions on Fitting Cabinet Connectors

Which drill bit is required for the cam lock casing? A standard casing requires a 15 mm Forstner or lip-and-spur cylinder drill bit. Special smaller variants are also available with 12 mm or 20 mm diameters.

What thread do connecting bolts use? Most bolts intended for direct installation in wood-based panels feature a Euro thread requiring a 5 mm pilot hole. Heavy-duty variants utilise an M6 machine thread combined with specialised threaded inserts.

Can cam and dowel connectors replace wooden dowels? No. The bolts primarily absorb tensile forces and clamp the components together. To handle shear loads and prevent the carcass from twisting, 8 mm wooden dowels should always be installed alongside the connectors.

How deep must the 8 mm edge drilling be? The edge hole only needs to be deep enough to fully enter the 15 mm cam recess. For a 34 mm backset, a drilling depth of around 40 mm into the edge is entirely sufficient.