WKCP structural timber screws
WKCP identifies a range of structural timber screws for connections between timber members. This page covers carbon steel screws with yellow zinc plating and a wax coating. WKCP is a product range designation, not a DIN or ISO standard.
Washer head, TX drive and thread
- Washer head
- The wider bearing surface distributes clamping pressure over the attached component. Unlike a countersunk head, it is not intended to sit in a conical recess in the timber; its position on the surface must be allowed for in the joint design.
- TX drive
- Use the matching bit: 5 mm diameter takes TX25, 6 mm takes TX30, and 8 and 10 mm take TX40. The bit must seat correctly in the drive.
- Thread length depends on size
- Longer variants have a partial thread and an unthreaded shank section. For example, 6 × 120 mm has a 75 mm thread, while 8 × 200 mm has a 100 mm thread. Thread length cannot be determined from diameter alone.
- Short variants
- For 8 × 40, 8 × 50 and 8 × 60 mm, the technical data sheet specifies thread lengths of 35, 45 and 50 mm respectively. The thread therefore extends closer to the head; the ETA specifies these sizes without a milling cutter above the thread. The geometry of a longer screw does not apply to them.
Material and surface finish
Material: carbon steel. Corrosion protection: yellow zinc plating. Lubricating layer: wax coating. Wax reduces friction during driving; it does not replace the protective function of the zinc coating.
The suitability of the finish for moisture exposure and the intended service conditions must be assessed against the documentation. Yellow zinc plating alone does not guarantee suitability for every outdoor application, persistently damp conditions or ground contact.
WKCP diameters and catalogue lengths
The overview lists specific sizes of the yellow zinc-plated WKCP range. Sizes are written as diameter × length, for example 6 × 120 mm or 8 × 200 mm.
| Diameter [mm] | Catalogue lengths [mm] | TX drive |
|---|---|---|
| 5 | 40, 50, 60, 70, 80, 90, 100, 120 | TX25 |
| 6 | 50, 60, 70, 80, 90, 100, 120, 140, 160, 180, 200, 220, 240, 260, 280, 300 | TX30 |
| 8 | 40, 50, 60, 80, 100, 120, 140, 160, 180, 200, 220, 240, 260, 280, 300, 320, 340, 360, 380, 400, 440, 480, 520, 560, 600 | TX40 |
| 10 | 120, 140, 160, 180, 200, 220, 240, 260, 280, 300, 320, 340, 360, 380, 400, 440, 480, 520, 560, 600 | TX40 |
The table lists the manufacturer’s catalogue sizes, not current JENPEX stock. Availability of the required size and configuration will be confirmed upon enquiry.
Measuring length: the WKCP drawing defines nominal length Lw from the bearing surface under the washer head to the tip. Head height is excluded. Thread length Lg is a separate dimension.
Cutting features and installation
WKCP documentation describes milling features at the tip, cutting notches on the thread and, for the applicable configuration, a shank cutter. They help cut timber fibres and reduce driving resistance. The additional thread at the tip assists initial engagement; it is not a second, separate thread beneath the head.
Check the presence of the shank cutter and the thread length for the specific size, particularly the short variants described above. The need for pre-drilling depends on the timber, screw size and joint design conditions. Installation must follow the manufacturer's instructions.
Applications in timber structures
Examples include connections in roof frames, timber frames and structural timber panels. The documentation covers solid softwood, glued timber members, CLT and LVL subject to the conditions of the applicable assessment.
For load-bearing connections, screw diameter, length, penetration and layout must follow the joint design and the manufacturer's documentation. The general purpose of the range does not mean that every size is suitable for every structure.
Manufacturer's technical documentation
The manufacturer publishes ETA-18/0817 dated 7 June 2023 for WKCP; the range dimensions appear in Annex 7.2. The ETA is a European Technical Assessment with defined conditions of use. Select the Declaration of Performance corresponding to the screw diameter.
- WKCP technical data sheet (PDF, EN)
- ETA-18/0817 (PDF, EN)
- Declaration of Performance WKCP-5/23 — 5 mm diameter (PDF, EN)
- Declaration of Performance WKCP-6/23 — 6 mm diameter (PDF, EN)
- Declaration of Performance WKCP-8/23 — 8 mm diameter (PDF, EN)
- Declaration of Performance WKCP-10/23 — 10 mm diameter (PDF, EN)
Related products and categories
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