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Why there are different dimensions for the same measurements on this drawing? For example 0.127mils and 0.097 mils pin to pin. Or highlighted 405 and 385 mils. I can't find anything on the datasheet indicating the difference?? Is this typical and max? Or typical and min? (some actually say max)

Need to know highlighted distance so I know where to place this part on the PCB. I could just make it 405mils to be safe, but I still want to know why they did this on the drawing?

Complete datasheet link below drawing. Thanks.

enter image description here https://www.mouser.com/datasheet/2/418/NG_CD_1218434_D1-1234416.pdf

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The link you've provided has a pretty comprehensive set of dimensions. One bit of text that jumped out to me is worded "See sheet 2 for recommended PC board layout."

I would read the reference of 0.127 / 0.097 as a difference of 0.030, which would then translate to 0.112 +/- 0.015 which appears consistent on many of the measurements. A couple appear a bit tighter at 0.020 or +/1 0.010 here and there.

The reference to Max is not so much to determine hole placement as it is to provide you with a dimension that the part will not exceed. If you allocate 0.225 for the shell, you'd have 0.001 clearance for the housing/components/accessories placed adjacent to that portion of the connector. It's not impossible to consider that the 0.224 Max could be measured at 0.220 which would still not cause problems for a design that allocates 0.225 in the housing/case.

Another location on the document specifies that the tolerance is +/- 0.010 unless otherwise specified. That means that the diagram on sheet two which has no tolerance listed individually for the PCB hole layout would be assigned that figure.

The above is a layman's interpretation mixed with a bit of mechanical drawing instruction and a good bit of tradesman's osmotic absorption from a career machinist (60+ years). It could be incorrect.

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  • $\begingroup$ More specifically, they are tolerances in the form of limit dimensions. The two stacked values represent the maximum (top) and minimum (bottom) allowable values. So any measurement within that range is acceptable. $\endgroup$ – Mark Apr 11 '19 at 1:41
  • $\begingroup$ For positioning it, start with the ".318 ref" (reference) dimension and work outwards from there. Note the ref dimension is to the "top" of the horizontal plate (or whatever it is) but the other dimensions are to the "bottom" of the plate - and the thickness of the plate itself will have a tolerance. $\endgroup$ – alephzero Apr 11 '19 at 17:13
  • $\begingroup$ All of that makes perfect sense. The difference is minimal so the design really wasn't at risk, but as an EE I don't see that much detail on drawings so I'm glad now I have a better understanding of how to read this. Thanks all for the answer and follow-up comments. $\endgroup$ – user3349039 Apr 30 '19 at 17:54

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