drilling plexiglass? thickness?

1" is what I would use on a peice that large. every 3" for screws, predrill with nice SHARP bit at lower speeds, to prevent melting. I almost always make a trim ring that goes around my plexi windows, so no one sees the scres, or cut edge.

pre plan, remember folks will be seeing the indise of the box now, so it much be clean, painted, & no screw tips sticking out.

good luck, have fun.

They sell special countersink bits, not specificly for plexi, but they work fine. I have also used a larger drill bit, & just tipped it in, so the head of the screw would be flat.

I usually do 2 steps, one smaller drill you can take through at higer speed, shure a little will melt, but keep an eye on it, & all the melted hould come out with the bigger slower bit. yeah, I LOVE these plexi bits. 1/8th is pretty small, so I would try things out on a scrap peice to get your confidence level up. Most custom shops have a scrap bin, just ask for a little peice, even a 3x3 peice you can make a bunch of holes in so you can get good at making them straight, & get the right drill speed.