Apparatus for forming a multiplicity of thin wafers from at least two similar blocks, the apparatus comprising a supply reel (1) to supply wire, an upper pair (3a, 3b) and a lower pair (3c, 3d) of parallel spaced roller guides and a collection reel (4); a wire from the supply reel passes around successive grooves along the roller guides from near the supply reel to near the collection reel, so to form a four sided continuous web of wires along the length of the roller guides. Part way along the roller guides, the wire is diverted around at least two pulley wheels(5a, 5b) removing the wire from the web after it has passed over a roller guide at a predetermined point, and reintroducing the wire into the web via a subsequent roller guide at a point laterally displaced from the point at which it left the web, so that there is a gap in the web of wire which divides the web into two separate sections, and no cutting action can occur in that gap.