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Imperial or Metric for PCB design? Its time!

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FreeThinker:
My Daughter had an Austin/Rover Metro car and strangely the brakes were held on with imperial bolts.Why? because the cost of tooling up to change them to metric was prohibitive. (I think they used the same brakes as the old Mini). What may seem like a small issue to you and me can be a big issue to a mass market producer, so imperial will be with us for many years to come.

FreeThinker:

--- Quote from: Squonk on March 11, 2012, 08:36:21 am ---
--- Quote from: FreeThinker on March 10, 2012, 10:19:52 pm ---My Daughter had an Austin/Rover Metro car and strangely the brakes were held on with imperial bolts.Why? because the cost of tooling up to change them to metric was prohibitive. (I think they used the same brakes as the old Mini). What may seem like a small issue to you and me can be a big issue to a mass market producer, so imperial will be with us for many years to come.

--- End quote ---
Perfect demonstration: Austin/Rover is dead now, and the new Mini has been designed by BMW, which uses metric bolts ;D

--- End quote ---
:)
However check out the number of failures in the 'new' minis due to engine/gearbox problems. I've been told by someone in the trade that it's mainly due to wear in the tooling producing the engines which is well past it's sell by date... so once again it all boils down to money!
But my point still stands as the Metro was built from old mini designed parts where as the new Mini does not (I don't think the brakes or engine are from the old mini) if they were you can bet that they would be imperial.
<Umm! Engine appears to be French :-X > :) :) ;)

sonicj:
1 ft lb = 1.36 N m

I memorized that one earlier this week while wrench'n on my truck (mitsubishi) with torque tools built for the US market.  :D 

converting from thou to fractions is painful. metric is easy.
-sj

Monkeh:

--- Quote from: sacherjj on March 05, 2012, 04:13:09 pm ---The US would have trouble going to metric board sizes, as 8'x4' plywood is a standard and would cause new board to not work in a repair situation if we had the slightly smaller 1.2 m × 2.4 m.
--- End quote ---

Actually, you'll find that's rounded down. They're 2440x1220mm. 8'x4' down well into manufacturing tolerance, let alone natural shrinking and swelling.

BBQdChips:

--- Quote from: Rufus on March 09, 2012, 09:53:46 pm ---The blog and comments look more like rants and drivel to me, like this from one of the comments

--- Quote ---Millimeters allow finer (and greater) granularity in the grid system to optimize the board real-estate, placement, via and routing grids.
--- End quote ---

--- End quote ---
It isn't just drivel, there's some truth to it.  Depending on how the software is written, the rounding error involved with conversion can become significant.  Just as shown with the example above (page 1) showing footprints not matching up because of the units used for their layout.

It's a lot like using a jewelers scale with a resolution of .002 grams.  Change units to grains (imperial) and now the resolution is .05 grains.  Do the math on those two, and you find that set to imperial, that scale has roughly 1/3 less resolution.  Same A-D, same sensor, same scale.  Change units, and it's bad karma.

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