Holes very close for dual board

I’m creating a keyboard PCB, and currently I’m maintaining two versions, one for ANSI and another for ISO. But I want to unify both in a single board. The problem is that some holes are quite close, and I’m afraid of having problems with them. One hole is the central hole for the Cherry button, and the other, located at 45 degrees, is for one part of the stabilizer.

imagen

I attach a capture of the 3D view of the zone: the bigger hole is for the Cherry button, and the smaller is for the stabilizer.

imagen

In this other capture you can see how the stabilizer is inside the holes (and also the central hole of the button, but in a real board, in each pair only one of both holes is used, never both).

What do you think? Is it safe to leave it that way?

The fab will be scared of the 2nd hole breaking out into the 1st hole, which would snap the drill bit

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One idea would be to use long holes or slits, instead of two holes. Many manufacturers can do them smallish

Maybe ask the fab. It could maybe be better to intentionally join the holes by making some sort of oval shape that they could mill out in one piece.

There is a minimum hole-to-hole clearance, typically 0.254 to 0.5 mm, required by fab houses. @Jonathan_Haas has a valid suggestion on that.

Thanks all for the answers. Since the holes must support a “clamp” in the case of the key stabilizers, I think that doing ellipses or similar things would not work, so I think that there are only two solutions:

  • forget the dual board, or
  • do the holes much smaller, and let the “final user” make the ones they need the right size, leaving the others untouched

Opinions?

An ellipse or slit is likely problematic, but something like this will probably still work and give enough area for clamping:

Bildschirmfoto vom 2022-09-15 15-17-29

It’s not complicated… Just make the two holes on the Edge_Cuts layer. You can add Notes to your Info to (whomever) that states/clarifies any concerns.

I’ve done this sort of thing many times before CNC milling my boards

PCB fab houses do this kind of thing all the time. Best to include Notes referencing them such as to include a drawing with Diameters and Note regarding the two sharp corners, Example:

Note: 1) Break Sharp Edges not Greater than 0.1mm

[FYI - ‘Break’ Edges, Corners… is the term Used by all Machinists]
You can simply draw them in Kicad on the Edge-Cut layer or in other programs, like FreeCad and export DXF and import to Kicad Video shows FreeCad–>Kicad and GIF below shows making the Holes in FreeCad.
And, of course, you can add a Radius to those sharp corners so they are not ‘Break Corners’ but rather a part of the Machined Cutout shape… That’s the appropriate way to do it!

ADDED: Here’s a Reference to BreakEdges…

note1

Two_Holes


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