Solid carbide spirals can be used in any application that other straight flute carbide tipped bits are used, such as trimming, shaping or grooving.  Spiral bits have a cutting edge that is constantly in contact with the material.  The load on the work piece and the bit is constant, uniform and draws less power than the conventional straight bit.  As a result more stock can be removed and faster feed rates can be applied.  The cut is a "peeling" action rather than a "chipping" action.  Spiral bits perform best at higher feed rates in a straight line and require more hold-down pressure.  Conventional straight bits will be more efficient at slower rates and where you have a lot of turns in the cut.