Cam Lock Connectors and Connecting Bolts: How to Create Hidden Furniture Joints

Together with a connecting bolt, a cam lock connector forms a positive-locking, demountable, and externally invisible 90-degree joint for furniture carcasses.

Anyone building wardrobes, chests of drawers, or shelving units inevitably faces the challenge of carcass construction. Glued wooden dowels are permanent, whilst standard wood screws inserted through the exterior spoil the appearance. The cam lock and connecting bolt system solves this issue. In this guide, you will discover the technical criteria for selecting the right furniture connectors, which drilling dimensions are essential, and how to carry out assembly without errors.

Key Buying Criteria for Cam Locks and Carcass Connectors

Choosing the correct fittings depends primarily on the board thickness of the material used (usually chipboard, MDF, or solid wood) and the required tensile strength.

Diameter and Height of the Cam Lock

The standard diameter for a cam lock connector in furniture making is 15 mm. Smaller variants measuring 12 mm or 10 mm exist for very thin materials (such as drawer sides), but are rare in conventional carcass construction. The height of the cam lock must strictly match the board thickness. For standard 16 mm thick chipboard, the drill hole for the dowel pin sits precisely in the centre at 8 mm. The cam lock therefore requires a height of approximately 12 mm to 12.5 mm to grip the hole optimally without breaking through the coating on the opposite side. For 19 mm thick boards, correspondingly taller cam locks (approx. 14 mm) are required.

Length and Thread of the Connecting Bolt

The connecting bolt is the counterpart that engages with the edge of the second board. Two dimensions are critical here:

1. The drilling dimension (length): This dimension defines the distance from the edge of the panel to the centre point of the 15 mm cam lock drill hole. Common standards include the connecting bolt 24mm and the connecting bolt 34mm.
2. The thread: Standard connecting bolts feature a Euro thread. This is screwed directly into a pre-drilled 5 mm hole. Alternatively, there are bolts with an M6 machine thread. These require the prior insertion of a threaded insert (Rampa insert) into the wooden board, which massively increases pull-out resistance in softwood or MDF.

Material Quality

Whilst simple carcass connectors for back panels or very light constructions are sometimes made of plastic, load-bearing cam locks must strictly be manufactured from metal. Die-cast zinc is the absolute industry standard here. The material is hard enough to withstand high tensile forces, but does not snap under slight overtightening. The matching connecting bolts are made of zinc-plated steel.

Types and Options at a Glance

The system works like a mechanical muscle that pulls two boards tightly together. For this to succeed, the components must be precisely matched to one another.

• Classic cam lock connector (15 mm): The standard for wardrobes and shelving units. It is tightened using a cross-head (PZ2 or PZ3) or flat-head screwdriver. Inside, there is a spiral curved track that pulls in the head of the connecting bolt when turned 180°.
• Connecting bolt with Euro thread: The fastest solution for industrial production and skilled fitters. Pre-drill with 5 mm, screw in the bolt, and it is ready. Often used as a connecting bolt in System 32 (hole line drilling with 32 mm spacing).
• Connecting bolt with metric thread: Used in combination with threaded inserts. Ideal for furniture that is assembled and dismantled frequently, as the thread cannot strip out of the chipboard.
• Special dimensions: In addition to standard lengths, shorter variants are available for tight spaces, such as the connecting bolt 8mm (often referring to the thread length inside the wood), alongside special lengths for thick side-panel constructions.

Which Connector for Which Application? (Decision Guide)

The combination of components depends on your specific project. Follow these guidelines:

If you are building a standard wardrobe from 16 mm chipboard: Choose a 15 mm cam lock (12 mm height) and combine it with a 24 mm connecting bolt. The 24 mm drilling dimension leaves enough material between the board edge and the cam lock hole to prevent the edge from breaking out under load.

If you are fabricating heavy workshop furniture or plinths from 19 mm or 22 mm material: Strictly use longer bolts, ideally the 34 mm dimension. Due to the greater distance between the cam lock hole and the edge, leverage forces within the material are distributed more effectively. A connecting bolt 34mm provides the necessary margin of safety here.

If the piece of furniture stands in plain sight (e.g. an open living room shelving unit): After assembly, the metallic head of the cam lock remains visible on the inside of the carcass. To ensure a neat appearance, cover caps can be pressed on or stuck on. To match the board decor, choose self-adhesive cover caps white for white melamine boards, self-adhesive cover caps wood for general wood finishes, or specifically self-adhesive cover caps oak for Sonoma or Wotan oak. For modern, dark furniture, self-adhesive cover caps black or self-adhesive cover caps grey are suitable.

If you are integrating drawers into the carcass: Plan the position of the cam lock connectors so they do not collide with the fixing points for runners. If you are fitting soft-close drawer runners, these will occupy the front hole lines in System 32. Position carcass connectors strategically between them or at the outermost ends of the base and top panels.

Installation Note: How to Drill and Assemble Correctly

Fitting cam lock connectors requires precise marking out and accurate drilling. Deviations of more than 1 mm will prevent the cam lock from gripping the connecting bolt.

Tools required:

• Drill or powerful cordless screwdriver
• Forstner bit (15 mm)
• Wood drill bits (5 mm and 8 mm) with centring point
• Depth stop for drill bits (strictly recommended)
• Screwdriver (cross-head PZ2 or matching the cam lock)

Step-by-step instructions:

1. Drill the bolt hole: Drill a 5 mm hole into the face of the first board (e.g. the side panel). The depth depends on the thread of the bolt (usually approx. 12 mm deep).
2. Screw in the bolt: Drive the connecting bolt in straight until the collar sits flush against the wood.
3. Drill the edge hole for the bolt: Now drill an 8 mm hole into the edge of the second board (e.g. the base panel). This hole must be located exactly in the centre of the board thickness (i.e. at 8 mm for a 16 mm board). The depth corresponds to the length of the protruding bolt plus 2 mm clearance.
4. Drill the cam lock hole (cup hole): Measure exactly the bolt drilling dimension (24 mm or 34 mm) from the edge of the second board. Position the 15 mm Forstner bit there. Drill the blind hole. The depth must correspond exactly to the height of the cam lock (e.g. 12 mm). Use a depth stop to avoid drilling through the panel.
5. Assembly: Insert the cam lock into the 15 mm hole. The small arrow on the cam lock must point towards the edge (towards the 8 mm hole). Now bring both panels together so that the bolt slides through the 8 mm hole and into the cam lock.
6. Locking: Turn the cam lock clockwise by approximately 180° using the screwdriver. You will feel noticeable resistance as the panels are pulled tightly against each other.

FAQ – Frequently Asked Questions About Furniture Connectors

How can I release a cam lock connector? To undo the joint, turn the cam lock anti-clockwise with a suitable screwdriver. Continue turning until the small embossed arrow on the cam lock points directly towards the connecting bolt (i.e. towards the board edge). In this position, the internal curved track releases the bolt head, allowing you to pull the boards apart.

Why is the cam lock not gripping the bolt? There are usually three causes: First, the drilling dimension (distance from the edge) does not match the bolt length. Second, the bolt was screwed too deeply or not deeply enough into the side panel. Third, the 15 mm hole for the cam lock was not drilled deeply enough, causing the cam lock to sit too high and miss the bolt head.

Which drill bit is needed for a 15mm cam lock connector? You strictly require a 15 mm Forstner bit or hinge boring bit. A standard wood or metal bit of this size would tear out the coated surface of the board and lacks the flat cutting geometry needed for a clean blind hole.

Are plastic or metal carcass connectors sturdier? Metal components (die-cast zinc and steel) are significantly sturdier and can take considerably higher tensile and shear forces. Plastic connectors are only suitable for lightweight assemblies, decorative fascias, or securing back panels, but not for load-bearing carcass joints in wardrobes or wall-mounted kitchen units.

Can I use cam lock connectors in solid wood? Yes, this can be done without issue. For dense hardwoods (such as oak or beech), however, it is advisable not to drive the connecting bolt directly into the timber, as driving it in is difficult and the bolt could shear off. Instead, use bolts with a metric thread (M6) combined with a pre-inserted threaded insert.