this point, the blowhole on the left has been enlarged, where
previously there was a 80mm hole. The right blowhole has not
been finished yet. My jigsaw blade broke, but fortunately I
had a spare one. If you are using a jigsaw or dremel I'll give
you this piece of advice: always try to cut INSIDE your marks.
You can always come back to make it a little bigger afterward.
The next picture show both blow holes done along the broken
we have big hole to mount fans, but nothing to hold them in
place. To make you screw holes, you will need a drill. The mesh
size to use depends on what type of screws you are using. Again,
use the fan to see if your marks are fine, its better to check
twice then be sorry. Before you start drilling, I used my dremel
to make a little crevasse in the center of each mark. This way
you are sure that your drill won't wandering when you start
piercing the hole.
metal with a jigsaw leaves you with rough edges which don't
look very clean and can be sharp. The best tool to clean those
edges is the dremel. If your blowhole is not perfectly round
you can retouch them with the dremel. However be careful when
using this tool on a side or top panel. You can easily scratch
the paint on them with this tool.