Just out of curiosity, how do you guys make precision - very clean exact holes? The only holes I need to be very precise are those where I am going to put my lens. Currently I am getting help but eventually I would like to make my own.
What makes it particularly hard is the fact the hole I need to make for the front is a bit bigger than 3/4"(20mm)
How do you guys make even bigger holes for you optics and such?
Since you didn't say anything about how much the equipment costs....I use my mill either with the rotary table or under CNC control. Makes very nice clean holes of any size.
If your question is how to make them fairly inexpensively, that's actually kinda hard. Your best bet would probably be with a cheap benchtop drill press with a bimetal hole saw. If you're doing this in thin metal, such as the front of a project box, you'll need to put a block of wood behind the piece of metal to support it. If you're pretty careful and with some practice you should be able to get reasonable holes. You may need to clean then up with a file a little. I don't think you'll have much luck using a hole saw with a handheld drill, you really need the stability of a drill press.
For years the only holes I could drill were egg shaped and in the wrong place but after years of practice and mistakes I can now get them spot on.
great tips from MtbMacgyver but a few others are to make sure that your tools are sharp, use a good centre punch berore you start, followed by a centre drill.
You don't say how you will be making holes but a boring bar on a lathe works good for me, with a four jaw chuck if you are working on a square object.
This is a vid of my madness and I hope that it helps:
EDIT: fujio I have just read your other thread. If you are drilling or cutting lower grade soft aluminium then use a slow speed and lots of oil to keep it cool as it would rather melt than cut.
I haven't tried this with big holes, but if you can find a tapered reamer with a large diameter that can be an easy way to neaten up a bad hole, as long as you don't take off so much the hole isn't the right size anymore.
I have only use it a few times but the step drill bit worked well for me as long as the material is not too thick. As previous posters have mentioned, you need to have a solid back block and clamp it down well.
I always use a mill and an end mill bit of the size hole required or my lathe. However for accurate larger holes by hand I usually drill a pilot hole no more that 25% the size off the hole required then drill the correct size hole after that. Make sure you use plenty of lubricant and ensure that the drill is sharp with both cutting edges of the bit the same length and angle. If one is longer than the other the drill will pull to one side and you will end up with an oversized hole.
I didn't really have a procedure, I just marked out the holes and drilled them..just making sure to keep the drill straight as possible.
I did however snap about 5 drill bits as they were only 1.5 or 2mm..
You can get an attachment that turns a hand drill into a cheap bench drill, its a cheap way to drill straight accurate holes. http://findingking.net/Bench-Drill-P...ource=GB&id=uk