How to Fit Cam Lock Fittings Correctly: Tightening Connecting Bolts for Rigid Carcase Joints

June 3, 2026

A cam lock fitting is a two-part furniture fastener comprising a connecting bolt and a cam casing that, through a rotational movement, creates a strong, invisible, and demountable 90-degree carcase joint.

Assembling furniture carcases requires precise joining techniques that ensure high tensile strength whilst permitting disassembly without damaging the material. The cam lock fitting (frequently identical in design or compatible with the Hafele Minifix system) is the industry standard for professional furniture construction and demanding DIY assembly. It consists of a cylindrical casing with an internal spiral groove and a matching connecting bolt.

This guide is designed for fitters, joiners, and keen DIY enthusiasts. It covers the technical requirements, exact drilling dimensions in millimetres, and the correct procedure for tightening the components to create a permanently rigid carcase joint.

How Cam Lock Mechanism Works

The mechanics rely on a simple yet highly effective principle: the head of the connecting bolt extends into the hole of the cam casing. When the cam is turned with a screwdriver, the spiral groove engages the bolt head. Due to the eccentric (off-centre) shape of the groove, the mechanism draws the bolt steadily inwards like an invisible clamp as it turns. This presses the two engineered wood panels flush together under high tension.

Required Tools and Materials

Precision is essential for professional installation and accurate drilling. A deviation of just 1.5 mm leads to uneven gaps or jammed fittings.

Drill or cordless screwdriver
Forstner bit: Ø 15 mm (standard size for the casing).
Wood drill bit: Ø 5 mm (for direct Euro screw threads) or Ø 8 mm (for wooden dowels and threaded inserts).
Depth stop / drill stop collar: Prevents drilling through the chipboard.
Drill guide / jig: For exact transfer of the drilling pattern (e.g. in the System 32 grid).
Screwdriver: PZ2 (Pozidriv) or PZ3 drive, less frequently TX (Torx) or hex key (Allen key) for tightening the cam.
Material: Cam lock fittings (casing and bolts), optionally wooden dowels for additional stabilisation against shear forces.

Step-by-Step Guide: Installing and Tightening Cam Lock Fittings

The following guide assumes a standard corner joint between two panels (e.g. carcase side to base panel). The most common panel thicknesses in furniture making are 16 mm and 19 mm.

1. Measuring and Marking the Drill Pattern

Positioning the holes is the most critical step. The distance from the edge of the face to the centre of the cam hole (the drilling centre distance) depends on the length of the connecting bolt used. Standard values are often 24 mm or 34 mm.

Mark the position on the face of the first panel (for the casing).
Mark the corresponding position on the edge of the second panel (for the bolt).
Ideally, use a drill jig to prevent angular errors.

2. Drilling the Holes

Pay strict attention to the drilling depth, especially on thinner panels.

Cam casing hole: Drill into the face of the first panel using the 15 mm Forstner bit. The depth depends on the panel thickness. For a 16 mm panel, the drilling depth is typically 12 mm to 12.5 mm. The drill bit must not pierce the decorative surface on the reverse side.
Bolt edge hole: Drill a channel (typically Ø 8 mm) exactly in the centre of the panel edge, leading into the 15 mm cam hole.
Bolt locating hole: Drill the hole for the connecting bolt thread into the face of the second panel (typically Ø 5 mm for direct wood threads).

3. Screwing in the Connecting Bolt

The connecting bolt is screwed into the second panel.

Drive the bolt in perpendicular using a PZ2 screwdriver.
Ensure that the collar of the bolt sits flush against the wood surface. If the bolt is inserted too deeply or at an angle, the cam will not engage correctly later.
In soft materials like MDF or for joints subject to heavy loads, fitting a threaded insert with a metric internal thread beforehand is recommended.

4. Inserting the Cam Casing

Insert the cam casing into the 15 mm hole of the first panel.

There is a small arrow or marking on the top face of the casing.
This arrow must point directly towards the edge hole through which the bolt will pass. Only then is the internal opening correctly aligned.
Press the casing flush into the hole. It must not protrude above the panel surface.

5. Joining the Components

Bring the two panels together. The head of the connecting bolt slides through the edge hole of the first panel directly into the open slot of the cam casing. The panels should now sit flush against each other at a 90-degree angle without gaps.

6. Tightening and Securing the Joint

This is the decisive moment for the stability of the carcase joint.

Insert the matching screwdriver (usually PZ2 or PZ3) into the cam casing.
Turn the cam clockwise.
After about half a turn (180°) to three-quarters of a turn (270°), you will feel clear resistance.
Tighten the fitting firmly by hand. The panels will be drawn together audibly and noticeably.
Important: Do not use brute force. If the cam jams before the panels meet flush, the bolt is seated incorrectly. Over-tightening can break the zinc die-cast casing or burst the chipboard.

Common Assembly Errors and Solutions

Even with careful preparation, issues can arise during assembly. Here are the technical causes behind common problems:

The cam turns continuously without tightening: This happens when the head of the connecting bolt is not caught by the spiral groove. The cause is usually a cam hole drilled too deep or a bolt screwed in too far. Check the drilling distance and back the bolt out by 1 mm to 2 mm if necessary.

A gap remains between panels: If the panels do not close completely upon tightening, wood shavings are often trapped inside the edge hole, blocking the bolt. Thoroughly vacuum all drilled holes prior to assembly. An angled bolt will also prevent a flush joint.

The wood cracks or bulges: If the cam is tightened with excessive torque (e.g. from an incorrectly set cordless driver), the bolt head is forced against the hole wall with extreme pressure. In standard chipboard, this quickly causes material breakout. Therefore, always tighten cam lock fittings manually using a hand screwdriver.

Integration into Furniture Construction

The cam lock fitting forms the structural skeleton of a cabinet unit. Once the carcase is squared and firmly tightened, functional hardware can be fitted. An accurately aligned carcase is an absolute prerequisite for moving components to operate smoothly.

Once the frame is rigid, concealed cabinet hinges can be mounted for the cabinet doors. For heavy doors, soft close concealed cabinet hinges are recommended, as the gentle closing action reduces leverage forces, protecting the carcase cam joints over the long term.

Internal fittings also rely on a twist-resistant carcase. When installing a 60 cm kitchen cupboard pull-out, the side panels must remain perfectly parallel so the runners do not bind. This applies equally to smaller configurations such as the 50 cm kitchen cupboard pull-out or slim larder units with a 30 cm kitchen cupboard pull-out. For drawer systems, full extension drawer runners are frequently screwed to the cabinet sides. Any inaccuracy when tightening the cam fittings directly compromises the running performance of ball bearing runners or undermount runners.

When building office furniture, a desk cable grommet is often recessed into the top panel after assembling the carcase to ensure neat cable management.

FAQ – Frequently Asked Questions about Cam Lock Fittings

How do I undo a cam lock fitting? Insert the correct screwdriver into the casing and turn it anticlockwise. Turn until the arrow on the casing points directly back towards the hole containing the bolt. The locking mechanism is now disengaged, and the panels can be pulled apart gently.

What is the standard size for cam lock fittings? In conventional cabinet making (wardrobes, sideboards), a diameter of 15 mm for the cam casing is the industry standard. Smaller 12 mm variants exist for lightweight applications, while heavy-duty versions with 25 mm or more are used for heavy loads (such as beds).

Are 15 mm cam lock fittings suitable for building a bed frame? For a sturdy bed frame, standard 15 mm cam locks are generally under-dimensioned due to the substantial dynamic shear forces involved. Dedicated heavy-duty bed brackets or structural steel connecting fittings should be used instead, which require deeper drill holes and thicker connecting bolts.

Can I replace a broken fitting (e.g. from flat-pack furniture)? Yes. The mechanics are standardised across brands. If the casing has a diameter of 15 mm and matches the panel thickness, you can easily replace broken components with standard replacements. Simply measure the length of the old connecting bolt from tip to collar to choose the correct replacement part.

Should I use wooden dowels alongside cam fittings? Yes, this is highly recommended. The cam lock primarily provides clamping tension (pulling the panels together). To secure the joint against lateral shear forces (panels shifting out of alignment) and to increase overall load capacity, one or two fluted wooden dowels (typically Ø 8 mm) per joint line should be inserted dry or glued.