Re: gEDA-user: [pcb] drill helper

[John Griessen <john@ecosensory.com>]

DJ Delorie wrote:
My local copy does this instead: If you check
> "drill helper", all pins are drawn with a much smaller drill hole.
>
> Comments?

Yes.  Great idea.

I've been effectively doing that by my hole specs for prototypes
not matching actual desired finished sizes.

When you make such "unreal" entries,
the data is less useful for simulations though -- you could not make an accurate
model of pads and vias for analyzing capacitance or transmission lines.

Having this optional and selectable without changing the "correct" design data
will be a benefit.

After my hand drilling experience, I feel guide holes of 1/4 the drill diameter
are beneficial down to .4mm (.016 inch).  1/4 is better than 1/3 dia since the shape of
a sharpened drill has the flat tip that is maybe 1/6 the diameter on the
high speed steel twist drills I have seen.

We have some suggestions that one ratio to drill diameter may not satisfy all, so I
would like to specify everything about a certain hole size in my design as a line
in the resource (Pcb) file for defaults,
and as a similar overriding line at the top of the .pcb output
file so PCB's output is as general as possible -- useful for manufacturing and simulating.
This entry would give corresponding drill size and drill helper size for desired finished size,
and override any default or formulaic sizes.


Wouldn't it be nice if one of the output drawings showed "standard holes and vias" in
a view that is just lines of vias/holes connected by traces.   Right when you start a design
before laying out any thing you could set your process etch undercut amount, then output
the "standard holes and vias" drawing to gerber, view it with gerbv to check that all your desired
standard holes were enough to get the design done with particular connectors and mechanical
details.

John Griessen



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