flat cut on end of extrusion
 

flat cut on end of extrusion
i'm making a part out of a round flouropolymer extrusion. both ends need to be trimmed to a flat end, or trimmed perpendicularly to the axis of the extrusion.
i've attached the drawing here. the drawing shows that the end of the part is cut at an even 90 degrees to the axis (datum a). my vendor is not making a very good cut, the surface drifts by about 0.05in.
what kind of tolerance could i put on this that would tell them to make a part that is cut flat (like it's drawn).
i can post some pictures of actual parts if this description isn't clear.
thanks
had trouble opening your attatchment. my answer is based on the 1994 version of asme y14.5m.
while the full answer will depend on end function, based on your description i would suggest considering a perpendicularity tolerance per section 6.6.4.1 of the standard.