Pack of 30 Koelner/Rawlplug construction screws, size 3.5 x 40 mm with partial thread and a countersunk (conical) head, intended for mechanical fastening of wooden elements, furniture assembly and joinery where a flush finish is required. These screws are designed to work with pre-drilled pilot holes and common power drivers to provide a reliable connection between timber components and composite wood boards.
Advantages
Partial thread enables strong clamping of joined wooden parts while allowing the unthreaded shank to act as a dowel to align components. The countersunk head provides a flush or slightly recessed finish suitable for concealed joints or subsequent surface treatment. Packaged in a set of 30, the screws are convenient for small to medium jobs and reduce the need for frequent reordering. The dimensions and geometry are compatible with standard drill bits and screwdriver bits used in manual and power tools.
Suitable for
- Joining two wooden pieces where a flush head is required (frames, battens, cleats).
- Furniture assembly and repair where partial thread improves clamping.
- Fixing trim, skirting boards and lightweight structural connections in timber work.
- Use with pre-drilled pilot holes in soft and some hardwoods and in particleboard.
When it may not be suitable
These screws are not intended for heavy structural loads where certified structural fasteners are required; they are designed for general construction and joinery tasks rather than primary load-bearing connections in engineered structures. They may not perform optimally in very dense hardwoods or in conditions with prolonged exposure to moisture or corrosive environments unless appropriate corrosion-resistant coatings are specified.
Key specifications
- Length: 40 mm
- Diameter: 3.5 mm
- Thread type: partial thread (shank portion unthreaded)
- Head type: countersunk (conical) head for flush finish
- Drive: compatible with standard screwdriver or power driver bits
- Quantity in pack: 30 pieces
How to use
Drill an appropriate pilot hole through or into the first workpiece according to the screw diameter and material hardness. Position the pieces to be joined and insert the screw with a compatible screwdriver or power driver, driving it until the countersunk head sits flush with or slightly below the surface. For best clamping effect, ensure the unthreaded portion of the shank spans the joint so that the threaded portion draws the second piece tight against the first.
What to consider before purchase
- Ensure 3.5 x 40 mm is the correct size for material thickness and required embedment depth.
- Confirm whether a corrosion-resistant coating is needed for outdoor or humid environments.
- Verify compatibility of your driver bits and that you will use pilot holes appropriate to the wood type.
Usage recommendations
Use pilot holes sized for the core diameter in hardwoods and slightly smaller in softwoods to avoid splitting. When visible finishes are critical, countersink slightly deeper and fill or cover the head with a suitable filler or plug. For multiple fastenings in a single assembly, pre-mark and space screw positions to distribute load evenly and reduce the risk of material splitting.
