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# Two major doubts with respect GD&T and tolerancing

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## Two major doubts with respect GD&T and tolerancing

(OP)
Hello I want to understand two things.

First, Im designing some parts and when I wanted to assemble them I took the worst case boundary as 0.3 considering the linear tolerance of 0.05 from both parts and then considering the tolerance of position and the perpendiculariry, but one Sr. engineer told me that the real interferance is 0.1 just considering the linear dimensions, why not considering the GD&T tolerances????

Second, I want to fully undestand how and why they make two or more datum reference frame besides ABC.

I want to become a master at this, I dont know why but I enjoy doing this, so if any one could tell me any advice or recommend any great book or courses that will be great!! I need a mentor!

### RE: Two major doubts with respect GD&T and tolerancing

diegoaml95,

We have a forum for this — forum1103: Drafting Standards, GD&T & Tolerance Analysis.

Your feature of size specifications allow the male part to be 0.05mm oversize, and the female part to be 0.05mm undersize. That adds up to 0.1mm interference.

I don't see any locating features or datums on your sketch. This makes your positional tolerance meaningless. Rule #1 requires the male part to have perfect form at MMC, making your perpendicularity irrelevant at maximum interference.

--
JHG

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