Spiral cutters utilise solid Cobalt/Tungsten square (inserts) usually 15mm square, 2.5mm thick and radiused sharpened to 100-150mm.
They are extremely tough and wear resistant for planeing all grades of timber (and other materials) and can be rotated to the four (4) sharpened edges and located accurately by indexed HT screws without any alignment or precision servicing.
When replacements are required as maintenance, after the fourth rotation, they are available in packs (10) in the quantity necessary for the complete cutter head.
A service tool that is calibrated to the correct screw tension(5.1 Nm) is available for $52.00