PCB FR4 as switch-plate: How big should the holes be? (JLCPCB)

[bogomips]

Hi guys!

I'm designing a custom board, and I'd like to make the switch-plate from PCB FR4 material.
This is pretty common.... Easier than getting metal plates CNCed or lasered...

Manufacturing by JLCPCB.

There are 2 caveats I can think of:
1) What size do I make the inner dimensions of the switch hole? (assuming its a square).
I have a CNCed switch-plate for another board I'm building. I measured it, and it's 14.09 in w and h. (Measuring a Cherry switch I have sitting on my desk - that is a decent size, and the clicks have enough foothold to click in).
My worry is this: the CNC tool used by JLCPCB... it has a radius, and also there is a tolerance for CNCing published by JLCPCB https://jlcpcb.com/capabilities/Capabilities as +-0.2mm.
When I set the dimensions of my switch plate hole - what should they be, and should I somehow account for the tool radius, and the tolerance of the CNCing?

2) The CNC routing of the PCB cannot create sharp corners... so you will have a radius.
How big? I dunno, but might screw up switch firment. I think is why you often see those "H" shaped / bevelled holes in switchplates:


Any advice would be much appreciated.

Thank you geekhack

[niakulah]

I'm currently researching for a similar project. I'm thinking of buying FR4 plates (without any copper) and laser cutting them.

Just an idea, I don't know if it'll work. If it does, then that would resolve your radius concerns.

[UnsignedPanda]

I've made a custom  FR4 plate recently that's 1.6mm thick. 14mm square worked for me. Keep in mind that you also need to round the corners in order for them to be able to make the cutout.
You can have a look at the Discipline65 source files on github, CFT made a kicad PCB file for a FR4 plate.

[Pylon]

For my board I just used 14x14mm cutouts with a 0.5mm radius. Had no issues with JLCPCB, though they did charge me extra for extra milling time making the plates. My files are on Github. Haven't had issues with switch fit.

[bogomips]

For Had no issues with JLCPCB, though they did charge me extra for extra milling time making the plates.

Hmm, interesting - now much extra? How do they compute that?

[Pylon]

It appears to be a flat $14.50 charge, at least for my plates. I got hit with the same charge when ordering 5 plates as when I ordered 25.