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tapped hole callout drill dia / draw vs model

Question asked by Steven Werr on Aug 24, 2016
Latest reply on Aug 25, 2016 by Chris Saller

This question straddles the line between model and drawing, but I think more relevant to this (drawing) group.


I'm a noob and also not a professional engineer so please be gentle.


There seems to be a good consensus (very well supported by ASME standard) that the drill diameter for a tapped hole should not be specified in a drawing unless there are specific design requirements.  I get it and it makes sense.


1. But what about the fact that drawings should be properly to scale?  The hole in a drawing is sized at the drill diameter is it not?  So the drawing is not going to be to proper scale for larger holes and/or larger scales.


2. Every shop I have used to have parts made wants a STEP file in addition to the drawing.  Do I just have to trust that the shop is going to drill the correct sized hole, ie they will reference the drawing for any holes instead of blindly going with the hole size in the model?


3. To the extent that I do know what the drill size should be, eg if I want 75% thread for soft metal vs 50% thread for hard metal, does the hole wizard have a way to modify the hole based on the material name/property?  Or would I have to create a new hole standard to accommodate different drill sizes "manually"?  It appears the latter.


I haven't seen this aspect of tapped holes discussed anywhere.  Have I hit upon something interesting, or is my inexperience showing?