ACS A-510-2 panel cutout dimensions
You're right. The only online info I can find for the Bendix/Gerdes/ACS switch is how to wire it. Not how big a hole it takes, or where the anti-rotation tab needs to be.
OK, second look on Aircraft Spruce website. I found this:
https://www.aircraftspruce.com/catalog/elpages/igswitches.php?clickkey=5735
Go down to the document titled "Drawing"(pdf file). But, I have to say I am not sure WTH this drawing is trying to convey...tab position I think, measured from......something....not sure what.
So, here are my panel dimensions, made by measuring an actual ACS A-510-2 start switch....way way back when I was doing my panel layout. The panel hole diameter is 0.620 inches. The anti-rotation tab is 20 degrees down, counterclockwise from the left horizontal axis. The end of the tab is 0.230 inches from the hole center. The tab is 0.080 inches wide. (Takes way more to explain it than if I just uploaded a fully qualified drawing.....but my CAD drawing is not fully dimensioned. To scale of course.)
Just so you know, the tab location above assumes the front label plate is horizontal on the panel (ie: zero bank angle), not set at some weird rotation angle.
If this doesn't work for you, or make sense, I can upload a dimensioned drawing. Let me know if you need that.
FYI, have to say this is my first reply here to someone in Bankok. Got to love VAF.