Required clearance for moving part (Push Button)

2017-05-17 22:03:40

I'm designing a push button made from most likely ABS but possibly TPE, it presses a surface mount button on a PCB with 0.9mm travel.

The ABS button is 8x8mm Square and travels through 4mm of polycarbonate

I want there to be very little (if any) wobble and as little gap around the edges as possible for aesthetic reasons. But I cannot have the button snagging or jamming as the product wears and the inevitable dirt build up.

How big should the cut out be?