Installing Shelf Supports for an Additional Level: Drilling 5 mm Shelf Pins for IKEA Kallax and Cabinet Furniture

June 25, 2026

A shelf support with a 5 mm pin diameter is the standard fitting for adding sturdy, retrofitted shelves to cabinet furniture within the 32 mm system.

Adding an extra shelf level to existing furniture requires trade precision. For carcases made from chipboard or MDF – compatible, for example, with common furniture systems such as IKEA Kallax – installing 5 mm shelf supports is the cleanest and most structurally sound solution. The technical challenge when retrofitting lies in drilling the holes perfectly level, aligned, and to the exact depth without drilling through the side panels.

This guide is aimed at fitters and experienced DIYers looking to create a reliable tier for their shelves. It covers accurate measuring, hardware selection, and the precise drilling process.

Difficulty level: Medium Time required: approx. 15 to 20 minutes per shelf

The Engineering Behind the Shelf: Fittings and Dimensions

Before reaching for the drill, the type of support must be defined. A shelf support generally consists of an insertion pin and a supporting rest. The 5 mm diameter has established itself as an industry standard in cabinet making, offering an optimum balance between load capacity and minimal material removal from the side panel.

Various designs exist, selected depending on the application:

Cylindrical pin: A simple steel cylindrical pin. It is unobtrusive, but offers only a very narrow, line-shaped contact area for the shelf.
Spoon shelf support: This variant features a flattened, spoon-shaped support arm. The load of the shelf is distributed over a larger area, reducing pressure marks in the shelf material.
Shelf support with collar: A raised collar between the pin and the support surface prevents the fitting from being driven deeper into the side panel hole under heavy loads.
Plug-in shelf support with locating lug: Here, an additional upward-pointing lug engages with a corresponding hole on the underside of the shelf. This locks the shelf against accidental pull-out.

For standard applications in shelving units and cupboards, the spoon shelf support made of metal or robust plastic is the most common choice. If you are planning glass shelves, dedicated glass shelf supports are strictly required. These feature rubberised cushions or plastic suction cups to stop smooth glass panes from sliding and prevent surface scratching.

Understanding the 32 mm System

Modern furniture manufacturing is based on the 32 mm system. This is a standardised grid dimension for rows of holes. When professionally extending furniture, sticking to this grid is recommended.

The rules of the system are:

The distance from the front edge of the side panel to the centre of the first hole is exactly 37 mm.
The vertical pitch between two holes is always 32 mm or a multiple thereof (e.g. 64 mm, 96 mm).
The hole diameter for shelf supports is usually 5 mm (less frequently 3 mm for delicate display cabinets).

By adopting these dimensions, you ensure that your retrofitted shelf aligns perfectly with any existing factory-drilled holes in terms of both appearance and structural load distribution.

Required Tools and Materials

For the professional installation of a new shelf level, you will need the following workshop equipment:

Drill or powerful cordless drill driver
Wood drill bit (Ø 5 mm) with a sharp brad point
Depth stop for the drill (alternatively: coloured masking tape)
Folding rule or precise vernier calliper
Try square or combination square
Sharp pencil or marking awl
4 shelf supports (5 mm pin diameter)
The shelf cut to size

Note on the shelf board: The dimensions of the shelf must be calculated precisely. Measure the internal clear dimension between both side panels. Subtract a total of 1 mm to 2 mm from this width. This clearance tolerance is necessary so that the shelf can be inserted smoothly without jamming, and to prevent changes in humidity from pushing the side panels outward.

Step-by-Step Guide: Drilling for 5 mm Shelf Supports

Accurate drilling is critical to the overall stability of the shelf. A rocking board is almost always caused by inaccurate measurements or misaligned drill holes.

Step 1: Define and Mark the Height

Determine the desired height of the new shelf level. Always measure upwards from the fixed base panel of the carcase to maintain an identical reference point on both sides.

Use the try square to measure exactly 37 mm inwards from the front edge of the side panel. Mark the intersection of height and depth with your pencil. Repeat this process for the rear support. The distance to the rear panel is less strictly standardised, but in practice is also frequently set to 37 mm or 50 mm from the back edge. Mark all four points (two on the left, two on the right) with utmost precision. A marking awl helps to make a small indentation in the melamine decor, providing a secure seat for the drill tip.

Step 2: Set the Depth Stop Accurately

Side panels of standard furniture (such as the Kallax system) usually have a material thickness of 16 mm, 18 mm, or 19 mm. In hollow-core or lightweight panels, only the outer skin is solid. Drilling through to the outside ruins the furniture irreversibly.

Measure the length of your shelf support insertion pin. A standard pin is typically 8 mm long. Set the mechanical depth stop on your drill to 9 mm. This extra millimetre provides the necessary clearance for the brad point of the drill bit and ensures that the pin collar sits completely flush against the side panel. If you do not have a mechanical depth stop, wrap a piece of masking tape tightly around the drill shank exactly 9 mm behind the tip. As soon as the tape touches the wood surface during drilling, the target depth is reached.

Step 3: Drill Holes at an Exact Right Angle

Position the tip of the 5 mm wood drill bit into the pre-punched mark. Align the drill at a strict 90° angle to the side panel. This is the most critical stage of the installation.

Drill into the material at a moderate speed with light forward pressure. The melamine coating must be cut cleanly to avoid chipping around the edges. As soon as the depth stop (or masking tape) touches the surface, stop forward movement. Pull the drill bit out slowly while it is still rotating. This extracts the wood shavings cleanly through the drill flutes. Vacuum the drill hole clean afterwards.

Step 4: Install the Shelf Supports

Take the shelf supports. Press the 5 mm pins into the newly drilled holes using thumb pressure. The fit should be snug with no play.

If the pin is tight when using solid metal fittings, tap it lightly with a rubber mallet. Never use a steel hammer, as this will deform the hardware. For spoon shelf supports, ensure that the flat resting surface faces squarely upwards.

Step 5: Fit the Shelf Board

Introduce the cut-to-size shelf slightly diagonally into the carcase. Lower it horizontally until it rests securely on all four supports.

Check the fit by applying gentle pressure to the corners of the shelf. It must not tilt or rock. A solid, flush contact across all four points ensures that weight is evenly distributed to the side panels.

Common Installation Errors and Technical Tips

Even with seemingly simple installation work, technical errors can severely compromise the durability of the structure.

Lack of perpendicular drilling: If the drill is held at an angle, the hole runs diagonally into the board. The inserted pin will sit crooked, causing the shelf to rest only on the edge of the fitting. This point loading creates massive leverage. Like a loose tooth, the support pin will tear out of the chipboard under load and destroy the hole.
Using the wrong drill bit: A standard high-speed steel (HSS) metal drill bit lacks a centre point. It will slip across smooth laminate surfaces. Use only sharp brad-point wood drill bits.
Ignoring load ratings: A 5 mm plastic support is suitable for lightweight decorative items. For heavy loads such as ring binders, tools, or stacks of books, solid metal fittings are essential. Under extreme loads, simple plug-in pins reach their limits. In such cases, consider using continuous steel shelf tracks or heavy-duty shelf brackets and supports that are screwed directly into the side panel.

FAQ – Frequently Asked Questions About Shelf Supports

How deep should a 5 mm hole be drilled for a shelf support? The drilling depth depends strictly on the length of the pin plus a 1 mm tolerance. For a standard 8 mm long pin, the hole must be drilled 9 mm deep. This allows the fitting to sit completely flush without the drill bit tip bottoming out.

Can I use 3 mm shelf supports instead of 5 mm? Technically yes, but this requires a 3 mm wood drill bit. 3 mm supports are primarily used in delicate display cabinets or lightweight display units. The shear force exerted on a 3 mm pin is considerably higher. For standard shelving in wardrobes or office units, a 5 mm pin is the mechanically safer choice.

How much weight does a 5 mm metal shelf support hold? The load capacity is determined not only by the fitting itself, but primarily by the pull-out strength of the side panel. In a high-quality 18 mm chipboard, a set of four solid spoon shelf supports made of steel or die-cast zinc will easily carry static loads between 15 kg and 25 kg. For heavier loads, screw-fixed shelf brackets or shelf supports should be installed.

What can I do if a 5 mm drill hole is stripped or too large? If the pin no longer grips, the hole must be repaired. Drill out the damaged hole cleanly to 8 mm. Apply wood glue (PVA glue) to an 8 mm wooden dowel and tap it flush into the hole. Once the glue has cured completely, drill a new, clean 5 mm hole in the exact same location.