earlier i had reported the following 
(the saga continues):

history
i used virtual shorts without problems for > 1 year
hundreds and hundreds of bds (turns out i was lucky)

one day a bd shop calls and offers to increase some tiny gaps ("no,
thanks!")

later another shop 'fixes' them without calling, causing opens
no big deal, a short run, blob a little solder

i investigate and conclude that using gerber 2.3 i too *could* 
see a 1 mil gap that they were seeing, but not always (i.e. not in every
VS instance)

i conclude that the problem was that i had shifted the origin from pin 1
to centroid in my VS part
did some gerber viewing and shipped another one to yet another shop
(it turns out this was almost the right conclusion)

a quick glance at the bds and they look fine
testing begins and then power which was running is lost to one section
the gap blew out, it was only maybe 800mA going thru a pretty beefy VS
pad part

looking at the bd you could see what did not look like a gap but did
look like a slight visual line in the solder plated pad

looking at the gerbers there was in 2 of 6 VS cases a 1 mil gap
(don't know how i missed that, i thought it was nailed)
i guess those guys can etch pretty good (i think i will start doing 1/1
bds!)

new conclusion, this fix works i am pretty sure
my original part had 60x75mil thruhole pads spaced at 75.005 mils apart
(depending on the positioning the gerber rounding can be benign or not,
this is why it always worked sometimes and sometimes worked other times)

my new part has 60x74.995 mil pads spaced at 75 mils apart
maybe this is what Lomax recomended from the outset and i just caused
myself some grief, i don't know

as long as the new part is placed on a 1 mil or greater grid i think the
pads will always bleed together now

i did a test at gerber 2.5 and camtastic still reports 0 gap between
objects using their inspection query tool
(which is as it should be since 2.5 is .01 mil resolution)

another problem solved i hope!
i am pursuing this because it is a very useful technique for certain
situations

you can steer the currents and control trace widths on an otherwise
common 'net'

i have made the schematic so that is not too messy by using a symbol
that appears to be a wire but has pins at the opposite ends so the
schematic reflects the intent 
it is not hard to read or as confusing as it would be if they appeared
as 'jumpers'

i have not tried the other technique he has described of using a
mechanical layer to create the shorts since making this VS work seems
more integral to me

there is of course the option of drawing a trace at the end of the
process and putting a wire in the schematic and sometimes this is the
best choice for certain situations

Dennis Saputelli


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