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Do tables of XY coordinates tarnish the souls of engineers?
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gnuarm:

--- Quote from: penfold on March 02, 2021, 04:35:05 pm ---One simply cannot compare round holes with square pads. Their shape alone is quite different let alone conventions for dimensioning them.
--- End quote ---

Square pads, round holds... don't care.  I see plenty of sheets that show dimensions from centers.  In fact I recall years ago asking a mech eng why they did drawings that way (you had to "assume" the lines were in the center) and he said that's the standard way of doing it. 
Berni:

--- Quote from: gnuarm on March 10, 2021, 03:36:58 am ---
--- Quote from: penfold on March 02, 2021, 04:35:05 pm ---One simply cannot compare round holes with square pads. Their shape alone is quite different let alone conventions for dimensioning them.
--- End quote ---

Square pads, round holds... don't care.  I see plenty of sheets that show dimensions from centers.  In fact I recall years ago asking a mech eng why they did drawings that way (you had to "assume" the lines were in the center) and he said that's the standard way of doing it.

--- End quote ---

Most datasheets from the big brands do it properly so that it makes sense when drawing in a PCB tool. For chips the measurements are even given standard designations, like pin pitch is always "e". When it comes to these devices i just run Altiums footprint wizard, type in the numbers and it spits out the correct footprint complete with a proceduraly generated 3D model and all.

It's more about those people that give you the footprint for some weird non symmetrical part that has SMD pins all over the place and they are all dimensioned between edges of each other, so you have to punch a bunch of numbers into a calculator to actually figure out where the center of a pad goes, usually to top it off the centers also don't fit onto any neat sensible mm or mills grid.
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