Although a V-block appears to be a standalone positioning component, its locating surface is actually a composite structure formed by two intersecting flat planes. This means the V-block doesn't rely on a single reference plane for positioning but rather uses a combination of surfaces, which significantly impacts how it should be analyzed and applied.
In typical locating components, the reference surface is often a single plane or a geometric element like a hole center, axis, or spherical point. However, when it comes to a V-block, its reference system consists of two key elements:
The intersection line of the two planes – used as a vertical positioning reference.
The center symmetry plane formed by the two angled surfaces – used as a horizontal reference axis.
Because a V-block is inherently a dual-plane positioning system, it cannot be analyzed or applied in the same way as single-surface positioning components. For example, in mechanical setups where a workpiece is located by one face and two holes, two locating pins are used. The positioning reference in that case is the imaginary centerline between the two pins, not the surface of a single pin.
Therefore, a single V-block cannot be used alone to achieve accurate and reliable positioning. For proper function and alignment, V-blocks must be used in pairs. This dual setup ensures stability and maintains the correct orientation of cylindrical workpieces during inspection, machining, or assembly.