It is never possible to maintain perfect concentricity between a thread and a bore. The resulting misalignment can cause side loads that will distort the cartridge body. This can have a significant effect on the spool clearance and may result in intermittent or unacceptable performance. Changes in the valve's internal leakage will also affect its contamination resistance and could therefore result in early valve failure.
A significant benefit of the Sun Hydraulics, cartridge system is the ability of the honed spool section to float relative to the cartridge's thread. This floating design will compensate for misalignments in the cavity.
This security also allows tighter machining tolerances to be maintained and therefore more reliable and better performing valves.