Valve Seats and Valves

In view of the importance of the precision of the surfaces that will be in contact and that, because of their complementarity, will ensure a perfect air tightness, OEMs tighten shape tolerances of the seat tapers (please refer to drawings on illustrations page). The linearity of the seat angle segment and its circularity are toleranced with valve differences not exceeding a few microns (<10 microns>. Ra and Rz values defining the surface finish of the valve seat and also very tight and the smallest chatter mark or undulation of the seat, yield a seat that is out of tolerance and unacceptable.

The tolerances applied to the notion of concentricity, runout or double runout between the axis of the valve guide and the axis of the valve seat also are very important yet remain within values relatively easy to guarantee.

Generally, concentricity defect/runout in the order or 0.05mm (.002") is considered acceptable. All these tolerance values are seriously tightened with the application of a coefficient called "cpk" issued out of the rules applicable to companies certified ISO/TS16949 and reduces considerable tolerance values through the use of machines capable of guaranteeing great consistency in quality.

This approach having for objective to guarantee quality is made possible since human error is avoided as much as possible owing to the muse of numerical systems triggering and controlling mechanisms yielding always more performance.

NEWEN Fixed-Turning comes within the logic of the evolved and high-performance mechanical principle, piloted and controlled with a unique high performance numerical control. The Fixed-Turning provides and guarantees:

  — Valve seat circularity <3 microns

  — Valve seat surface finish <Õra 0,4 (if the material allows it)

  — Segment linearity <0.004mm (4m)

  — Concentricity between the valve guide and the valve seat: <25m for H6 valve guides and <30m for H7 valve guides.

This level of quality is the highest today and is accessible to all people machining valve seats, from the smallest engine rebuilder to the largest production facilities using NEWEN Fixed-Turning.

Lastly, NEWEN Fixed-Turning is a reliable and consistent production means, economical and flexible, allowing to take into account the most severe Cpk while controlling one's profits.