Tolerance for Valve seat

[Blue_V]

Hi,
Im new to GD&T and getting to grips with the usage and understanding. So I was going through this link

QUALITY CRITERIA Brochure ENGLISH.pdf.


Here (page 14) it says valve seat is controlled using circularity and concentricity. Why not use total runout ?

Thanks and Regards,
Blue_V

[Kelly_Bramble]

Here (page 14) it says valve seat is controlled using circularity and concentricity. Why not use total runout ?

Good question! I think the geometric definition required would depend on whether or not the valve stem restrains the relative position of the valve. Should the valve stem not restrain the relative position on the valves against the valve seat then the only requirement would be the cylindricity and circularity match that of the valve sealing seat.