SEBO Stainless A2 Screw 3.9 x 13 (DIN 7981-A2) for DUO

The A2 suffix is the whole story here. This 3.9 x 13 is made in A2 stainless steel instead of the plated steel used for most SEBO fasteners, and it is the screw SEBO specifies for the DUO, where an ordinary one would be exposed to moisture. The form is otherwise the familiar DIN 7981 shape, a cross-recessed pan head on a self-tapping thread, so it fits and drives exactly like its plated equivalent.

Corrosion does more than spoil the look of a fastener. Rust expands in the thread and locks the screw into the plastic around it, so the next attempt at removal either shears the head off or tears the boss out along with the screw. Stainless keeps the joint serviceable years later, which matters most on screws that only ever come out during a repair and are therefore left undisturbed for the longest.

• Part number: 106
• Fits: SEBO DUO
• Material: A2 stainless steel
• Specification: 3.9 x 13 to DIN 7981-A2
• Head and drive: cross-recessed pan head
• Sold: each
• Plated-steel screw of the same size: part 102, an F 3.9 x 13 to DIN 7981

Do not substitute a plated steel screw of the same size in this position, however well it fits. The dimensions are identical and the service life is not. Replace one when the head has rounded, when it no longer holds torque, or simply while the area is open for other work, since fitting it takes no longer than refitting the old one.

Telling the two apart on the bench is straightforward once you know to look. A2 stainless has a duller, greyer surface than bright zinc plating and carries no plating to flake away at the edges of the recess. If a screw removed from this position shows rust staining around its head, it was not the correct part and the seat underneath is worth inspecting before anything new goes into it.

This listing answers searches for a SEBO DUO stainless screw, a DIN 7981-A2 3.9 x 13 replacement, a SEBO corrosion-resistant fastener and a genuine SEBO 106. Genuine SEBO part from an authorized dealer, shipping in 2-5 business days.