--- In [email protected], NeonJohn <j...@...> wrote:
>
> I'm making the transition from the handholding of ExpressPCB CAD to the
> wild and woolly world of KiCad :-) An area where I can see me getting
> into trouble very easily is with drill sizes since KiCad allows one to
> enter any drill size. Questions:
>
> * How does one know what the standard drill sizes are?
It's up to the board house.
> * Is the drill size the drilled hole size or the size of the hole after
> plating?
It's up to the board house.
> * if the drilled hole, how much should I allow for plating build-up?
For a rule of thumb, the finished hole will be about 3 mil smaller than the
drill size, so a 0.042" drill (size #58) will yield a 0.039" diameter hole.
It does vary, however. A board house that's setup for (and wants) on-line
business should make it easy to get the information. For example,
http://www.pcbexpress.com/technical/faq.php#drills provides a listing of drill
file tool sizes versus finished hole size (their nominal specs are "you tell us
the finished hole size").
Absent that, you can probably only make the assumption that a drill size is the
pre-plating size, then figure tool tolerances and plating tolerances to come up
with a reasonable dimension.
