Originally Posted by Cabbs
I used a Dremel with a cutting wheel, but if you can find a 120MM hole saw for a power drill I hear they make clean cuts if you don't let it jump. Before you make the cut, cover the panel with blue painter's tape and draw the template on the tape. If it jumps, it'll hit the tape first and reduces the risk of scratching the panel.
What cabbs didn't tell you was all the time it took to stone grind and polish up the edge. Nice job though. Looks good.
As for me I find making the circle with a coastered cd gives me a neat 120mm circle. Like cabbs my tool of choice is the trusty dremel. Steel panels will eat up the cutting disks so have plenty on hand or get the really good ones to start off with.
Also like cabbs said mask up the surface and draw your template on that. When making the template drawing don't lose site of the center of the long axis. If you do your cut will be off center.
Measure from center to outer edge of template circle (This is to make sure whatever you drew around didn't move)
On the short axis measure from edge of circle to edge of panel (both sides from circle to edge should be the same)
Find safety glasses and ear plugs
Put them on (Trust me that little SOB makes a lot of racket and there's crap flying everywhere)
Make sure anything you don't want covered in grinding debris is covered up.
Take wiz (Never fails when you start cutting your bladder decides it's time to empty itself)
Check the time (If you don't your neighbors damn sure will)
Fire up the dremel and begin cutting
TAKE YOUR TIME (You're wanting this to come out right, don't cha?)
Get the stone attachment and clean up the sharp edge you just made
Leave template right where it is
Oh joy ain't it purdy? The fun ain't over yet. Now lay that fan over the hole and center it up. You have to have something to make make marks accurately where the mounting screws go. Cutting the hole is nothing if you screw this up. I use a 1/8 drill bit and just slide it in the hole and give it a little twist or two by hand. If you can't seem to get the fan to stay put have some one else hold it in place and wrap some tape around it and the panel.
Drill out the holes for the mounting screws then mount that sucker.
Go have a beer. At this point you'll need one...