Connecting Bolts 8 mm to 34 mm: Choosing the Right Length for Cam Lock Fittings

Together with a cam lock housing, a connecting bolt forms a positive-locking furniture connector whose correct length depends on panel thickness and precise drilling dimensions.

In cabinet construction, the cam lock fitting is the undisputed standard for right-angled board joints. For joiners and fitters, selecting the matching bolt is essential for carcass stability. An incorrect drilling distance leads to open gaps, whilst an unsuitable thread causes tear-out under load. This guide breaks down the technical specifications of connecting bolts and helps you find the exact dimensions for your furniture project.

Key Purchasing Criteria for Connecting Bolts

Choosing the right furniture connectors depends on practical factors: panel material, material thickness, and the drilling pattern used. Pay attention to the following parameters:

1. The Drilling Distance (Centring Distance)

The drilling distance defines the measurement from the edge of the board to the centre of the hole for the cam lock housing. It determines how far the bolt extends into the mating piece. Industry standards are 24 mm and 34 mm. A deviation of just one millimetre prevents the cam from gripping the bolt head or tightening sufficiently.

2. Thread Type

The section of the bolt screwed into the wooden board determines pull-out resistance.

• Euro thread: Designed for direct drilling into chipboard or MDF. Usually requires a 5 mm hole. The asymmetrical thread profile cuts directly into the material to offer superior grip.
• Metric thread (M6): Used in combination with a threaded insert or a tee nut. Ideal for furniture that is assembled and dismantled repeatedly, as the wood thread does not wear out.

3. Material and Drive

Bolts are generally manufactured from galvanised steel or die-cast zinc. They feature various drive types for insertion. Common options include cross recess (PZ) or a hex socket drive. Slotted drives can be found on older fittings.

Whilst wood screws and furniture screws create a permanent, non-demountable joint, the cam system allows the furniture to be disassembled at any time.

Lengths and Dimensions at a Glance: 8 mm to 34 mm

Dimensions specified for connecting bolts can refer to different parts of the component. Most often they denote the drilling distance, but occasionally refer to the thread diameter or the length of the threaded portion.

• Connecting bolts 8 mm: This dimension typically refers to the neck diameter of the bolt or the required hole for specialised insert sleeve systems. An 8 mm thick shank provides increased shear strength in heavy-duty constructions.
• Connecting bolts 24 mm: The standard drilling distance for thinner panel thicknesses of 15 mm or 16 mm. The shorter leverage path is ideal for lightweight carcasses, drawers, or small wall cabinets.
• Connecting bolts 28 mm: A less common intermediate size, often used in specific proprietary systems or custom builds with non-standard panel thicknesses.
• Connecting bolts 34 mm: The standard for solid carcasses, wardrobes, and panel thicknesses of 18 mm, 19 mm, or more. The longer drilling distance places the hole for the cam housing further into the centre of the board, preventing edge blow-out under heavy loads.

Which Bolt for Which Application? (Decision Guide)

Matching the connecting bolts to your project follows clear technical logic.

• Building a standard carcass from 16 mm chipboard: Choose a drilling distance of 24 mm. A 34 mm hole would sit too close to the edge or surface on thin boards, weakening structural integrity.
• Constructing heavy wardrobes from 19 mm MDF: Always opt for the 34 mm drilling distance. Leverage forces from large doors and heavy shelves require the cam to be anchored deeply within the material.
• Planning a central partition with opposing shelves at the same height: Use specialised double-ended connecting bolts. These pass through the central divider and engage into cam housings on both sides.
• Furniture intended for frequent dismantling: Avoid driving a direct Euro thread into the timber. Instead, fit a threaded insert into the wood and use a bolt with a metric thread.

Installation and Fitting: Setting Cam Connectors Correctly

The cam lock connector works like an internal clamp inside the wooden panel. When the housing is turned, it grips the head of the bolt and pulls both boards together with significant force. Precision during marking out and drilling is essential.

This is often carried out using the System 32 standard, a regular drilling grid in cabinet making where hole centres are spaced in multiples of 32 mm.

Required Tools

• Cordless drill driver
• Wood drill bit (typically 5 mm for the thread)
• Forstner bit (typically 15 mm for the cam housing)
• Pozi screwdriver size PZ2 or a hex key

Installation Steps

1. Drill the hole for the bolt: Drill a 5 mm hole into the face of the first board. Ensure the correct depth (usually 11 mm to 12 mm) so the board is not pierced through. A depth stop on the drill bit is strongly recommended.
2. Drive in the bolt: Screw in the connecting bolt perpendicularly. The collar of the bolt must sit flush against the board surface. Do not overtighten, to prevent stripping the wood thread.
3. Drill the edge hole: Drill a hole (usually 8 mm in diameter) into the edge of the second board, positioned to align precisely with the inserted bolt.
4. Drill the cam housing hole: Use a 15 mm Forstner bit to drill into the face of the second board. The distance from the edge to the centre of the hole must match the drilling distance exactly (e.g. 24 mm or 34 mm).
5. Assemble: Push the panels together. The head of the bolt should now be visible centrally inside the 15 mm hole.
6. Lock in place: Insert the cam housing (with the arrow pointing towards the bolt) and turn it clockwise by approximately 180° using a screwdriver until firm resistance is felt and the joint pulls tight.

Frequently Asked Questions (FAQ)

How do I release a stuck cam connector? Turn the cam housing anticlockwise using a suitable screwdriver until the small arrow indicator points directly towards the connecting bolt. In this position, the lock is fully open. If the panel does not separate, tap the wood gently with a rubber mallet to free the joint.

What does drilling distance mean on a connecting bolt? The drilling distance is the precise measurement from the edge of the board to the centre point of the hole drilled for the circular cam housing. The most common standards in furniture manufacturing are 24 mm and 34 mm.

Can I replace a 24 mm bolt with a 34 mm bolt? No. The drilling distance of the bolt must strictly match the position of the hole drilled for the cam housing. If the housing is drilled at 24 mm, a 34 mm bolt will protrude too far into the cavity and cannot be gripped by the cam.

Which tool do I need to screw in the bolts? This depends on the drive type on the bolt head. Most modern connecting bolts feature a cross recess drive inserted with a PZ (Pozidriv) screwdriver. Heavy-duty bolts often require a hex key.

Why is the cam not gripping the bolt head? This typically happens for two reasons: either the connecting bolt has not been driven deep enough into the timber (the collar is not flush), or the drilling distance for the cam housing deviates by a few millimetres. Check both the insertion depth and the drilling measurements.