How DRC determines hole to hole distance for "Drilled holes too close together" error

[MrTn]

Hi to everyone,
I read every post on forum that I have been able to find on this topic but without success.

I have a very unusual error in DRC, actualy a lot of those.
At the first glance, error is very decriptive and self explanatory:
“Drilled holes too close together (board setup constraints min 0.4995 mm, actual 0.3765 mm)”

and also, settings are correct:

BUT

The vias in error are actualy 0.581 mm apart, as can be seen in the following image:

My first hypothesys was that KiCad calculates distance between walls of vias (0.581 - r1 / 2 -
r2 / 2). But even in this case distance would be 0.381 and not 0.3765. And also, I found many sources that claims that distance is “center to center”.
I am using version 7.0.1

So, I actualy don’t know whati is happening. What is the way that this distance is computed? Does anyone have the same problem? Or might it be an issue in KiCad itself?

Best regards, Martin

[RaptorUK]

@MrTn

My first hypothesys was that KiCad calculates distance between walls of vias (0.581 - r1 / 2 -
r2 / 2).

That should be 0.581 - r1 - r2

But regardless . . .

@MrTn

0.381 and not 0.3765

. . . both these figures are less than 0.5.

If the illustration is correct the 0.5 is between the hole walls not the centres.

[eelik]

@MrTn

And also, I found many sources that claims that distance is “center to center”.

That doesn’t make sense for manufacturability. Edge to edge (nearest edges, of course) are important because drilling doesn’t like an edge – be it another hole or board edge – nearby the edge of the drill bit. Two reasons: first, the other hole may bend and break the bit if they overlap. Second, a thin wall between holes may break. Naturally the diameter of the holes affects this and it doesn’t make sense to measure center to center.

[MrTn]

Thanx for answer. About the formula: you are absolutley right, I ment to use d-s and not r-s
And thanx for info. Obviously this is “wall to wall” not “centre to centre”.

[MrTn]

eelik, you are right. Icon is quite obvious
Thanx to you too.

[MrTn]

Obviously this rule is not considered in “Shove” mode. Becouse exactly moving vias around with Shove option allowed me to put vias so close.

[Piotr]

@MrTn

But even in this case distance would be 0.381 and not 0.3765.

Do you know that holes are drilled bigger than you specify to have after plating (it has no thickness 0) the diameter you specify?
May be KiCad adds it to the calculation.