Sorry if this is the wrong area, but I couldn't see any better ones.
My project is in a somewhat larg PLATIC box.
3 mm thick.
For the sake of not having to take the box appart and all the stuff like that, I am wanting to put a USB socket on the side.
Alas the socket is 23mm diamater! Maybe 24!!
I have asked and a couple of options have been mentioned:
A lot of small holes around the edge of the big hole area and knock it out when complete. Ofcourse this would then mean having to smooth the edges of the hole to make it round rather than "star" edged.
Hole saw? Mine go up to 75mm.
Yeah, but the teeth are more for wood cutting than plasttic.
The last thing I want to do is break the plastic box.
If you have any worries use it in a hand drill and take your time.
Coping saw then a dremel drill with a round emery wheel installed to clean it up
Start with a smaller hole, then use a tapered reamer to enlarge it.
I agree completely with starting small and then using a tapered reamer. You'll get a much cleaner hole that way.
However, if such is not available to you, then use a spade bit, but be sure to get one with cutting spurs at the edges, such as this (http://www.drillspot.com/products/78050/speedbor_88820_wood_boring_spade_bit). In a non-metric size, you'll want either 7/8 or 15/16. Go slowly, and use a piece of scrap wood as a backing block when drilling your hole.
A hole saw will work just fine.
Look for a hole saw of some type...
These are very useful for drilling round holes in plastic, http://www.amazon.com/Neiko-Titanium-Step-Drill-Bit/dp/B000FZ2UOY/ref=sr_1_1?ie=UTF8&qid=1342737118&sr=8-1&keywords=unibit
When the hole is not round (ie. square) I drill a round hole and then use a file to square it up. Doesn't take long and given a little practice produces nice results.
Both tools work with plastic as well as sheet metal.
Surprised how many people don't know about nibblers.
I would carefully mark the cutout I need, drill a hole somewhere inside the area, then nibble out to the edge and around the perimeter. Very minimal filing or sanding after that, if any. You can make a nice square hole this way if you need it.
I love nibblers, been using them for years, but the ones I know about can't to 3mm.
I haven't had much success with nibblers on plastic. Everytime I have tried I end up with cracks. Filing doesn't take very long. A good range of files should be in everyone's toolbox.
I'd agree with the suggestions to drill/hole saw undersize and then file to the exact fit.
there's always good old fashioned routers