Pneumatic questions, sorry!

[Max]

here is a quick (and not to scale) drawing of my bot
[attachment=0:39r7ibiy]hole drum spinner robot wwith removable lid info.jpg[/attachment:39r7ibiy]
i can't think how i can explain it any further basicly i just want to be able to bolt my aluminium lid onto my 20mm hdpe bot without having to tap a hole for the bolt as i think the thread would strip easily (thats why i want a course thread, to help prevent it ripping out) or would wear out over time with all the bolting and unbolting to do repairs or charge batteries