Mine came with a gap before they were "fixed" which basically meant adjusted once they were in place. This should be something can be adjusted. Mine appear to be touching but aren't if you get really close. HTH

For full overlay...as close as possible without them interfering with each other.

For partial overlay...it depends on your preference and the width of the vertical stile b/w the doors (assuming there's a vertical stile). If there's no vertical stile, see "full overlay."

For inset, the standard gap all around is 3/32" - about the width of a nickel.

Most cabinet manufactures spec 1/8" here.

3/32 is best, 1/8 is too wide

thanks for all the replies

Caveat: most cabinet makers have some give room somewhere along a wall of cabinetry so that if your walls are not squared (house settling, whatever) they can take it out of that little give space. You should not need it between every set of double doors, but somewhere along the run, it is wise to do so.

My friend's KD did not plan this and it was a mess because her walls weren't quite square when they went to put them in.

Any cabinet maker worth his salt know how to field measure.
The walls not being plumb is a matter for scribes and not for door reveals.

My doors are full overlay. So I will try to reduce the opening as much as possible so they do not rub.

Does this spacing hold true for the gap at the hinge location between the door and the cabinet box?