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Dowel hole depth callout for GD&T in thick material

Question asked by Michael Ponte on Dec 6, 2016

Is there a/ whats the best way to say you only need to hold a true position of .002" for the first .250" of a dowel hole and the rest can be held to .020". 


Background info on why and what I'm trying to do:

I have some dowel holes that have to go all the way through a part for venting.  Typically I would give a dowel hole a true position tolerance of .002".  The problem I'm running into is these thru holes will have to go through about an inch of material and I know the machine shop isn't going to like holding a tight tolerance through that much material.  I only need to hold that tolerance for the first .250" of the hole.  Sometimes I will add a larger "relief hole" (mentioned in a similar unanswered post) with a true position of .010" or more coming from the other direction, effectively removing the most of the depth of the dowel hole.  The only problem with this is it adds unnecessary cost to a part.  Any examples of a callout would be great.