The horizontal or flat joint is a kind of finger jointing connection.

For the horizontal joint, the zinc profile is milled parallel to the wider side of the workpiece. Thus, only on the narrow side a zigzag profile is visible, in the area only a butt joint is created.

Application

The horizontal joint is primarily used where high-quality plates are produced and thus, a zigzag profile in the area is undesirable. Occasionally, one finds the horizontal joint in compact machines, in which the router head is positioned vertically and the workpiece is transported flat.

Advantages

• No zigzag profile visible in the area
• At the same workpiece dimensions, compared to the vertical joint, a lower milling height is required, resulting in lower motor power, shorter spindle length and tool height. Thus, the milling machine can be designed more lightweight.

Disadvantages

• For package plants, significantly reduced capacity of the milling machine
• For many profiles 2 milling tools are necessary and thus, either a second milling machine or a lifting spindle
• For many profiles different milling tools are also necessary for different workpiece thicknesses.
• For several profiles up to 2 scoring aggregates are necessary.

Versions

Since the horizontal joint is primarily used for aesthetic reasons, it has to avoided that outbreaks occur when planing finished, jointed workpieces, because the outer tines were cut half or that the adhesive shines through the cut tines.

Therefore, the so-called Schulterzinkung (shoulder joint) is usually used. Here the outer edges of the zinc profile are designed as straight joints from the outset.

Examples for shoulder joints:

• Positive-negative
• Half shoulder
• Changing shoulder

Another version is the Trapezzinkung (trapeze joint). This is mostly used for relatively thick workpieces in which the zinc profile is even clearly visible using the horizontal joint, and when a more pleasing appearance is desired.