Marking out and Measuring
With placement chosen we next need to mark out the cuts and drill holes and to do this we will need a ruler, compass, pencil / marker and a tape (medium tack).
Taping off the cutting area isn't compulsory, but is a good habit if you want to keep your paint job clean and blemish free. Taping the area also makes marking out dark cases much easier as well as keeping the paint from chipping while cutting which in the long run will save you some extra clean-up work.
With our work area taped up, mark out roughly where you want the center of your fan to be - center up if necessary using your ruler. Set your compass to the necessary size using the guide below, and once correctly set, proceed to draw out your desired fan size. It is best to try and draw one clean circular line to save confusion when cutting out. If your circle doesn't join up, erase and start again.
Tip: Your compass needs to be set to the following sizes for the corresponding fans:
80mm fan = 40mm
92mm fan = 46mm
120mm fan = 60mm
140mm fan = 70mm
Finally we want to mark out the drill holes for the mounts. Line up a fan over the top of the circular compass markings previously made. I find the easiest way to mark the holes is to take the center out from a ball point pen, and this will fit straight through the fan mount.
Check that the fan is lined up by placing the pen through and wiggle on the tape beneath. This will leave a pen mark on the tape - repeat this process for the remaining three fan mount points. When you remove the fan you will be left with four perfect fan mount markings just waiting to be drilled.