Valve seat machining with HNHX indexable inserts

To further lower the cost per part when machining valve seats in the cylinder head, MAPAL has developed the new HNHX indexable inserts.With up to 24 usable PcBN cutting edges, they are not only particularly economical but also make the most effective use of the cutting material. Thanks to the high-quality cutting edges, the new HNHX indexable inserts allow for surface finishes greater than Ra 0.2 μm.

The newly designed machining star guarantees uniform pressure distribution when clamping the indexable insert. The development expands the range of application for valve seat tools because the clamping screw had previously prevented their use in certain valve seat diameter ranges.

The stock HNHX inserts are hexagonal like their HX predecessors, but unlike them they can be turned, which doubles the number of available cutting edges from six to twelve. This is made possible by the negative mounting position and the cutting material used.

The use of coated indexable inserts enables optimum utilisation of the cutting material. The coating makes a colour change or wear on the cutting edges visible. Wear or damage can thus be recognised in time and the indexable insert can be replaced if necessary.

Where it is constructively possible, for example with larger valve seat rings in the truck sector, each of these cutting edges can be used twice, making 24 cutting edges usable. This is done by removing a cutting edge at the end of its service life and reinserting it in a different angular position, allowing further work to be carried out with an area of the cutting edge that is still unused. Whether the insert can be used at two different angles must be determined by examining the respective component. In any case, there is a significant reduction in the cost per part.