How To Cut Fan Holes

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Being new to building pc’s I’ve got lots of questions but not a lot in the way of answers to balance things out. On another thread I told someone how not to cut a hole for a fan, not that helpful. I've cut a lot of holes in a lot of different things, so I thought I’d do a step by step..... much more helpful.

This method has a few stages but each stage is easy and makes the next one easier and results in a smooth round hole ;)

You could use a jigsaw rather than a Dremel but they are always a bit of a pain on thin sheet metal and you’ll have to finish the hole by hand anyway if you want it halfway decent. Also I needed to cut through some cooling slots, the jigsaw would have made a mess of these.
It took me a couple of hours for two holes.

What you’ll need:
A Dremel and some metal cutting discs
Electric drill and a 1mm or 2mm drill bit
Half round hand file
Set square, ruler and pencil
Compass and divider
Masking tape
Eye and ear protection

Health & Safety :)

If you’ve not done anything like this before it’s worth mentioning that when you cut metal it gets hot and is rather sharp. A hot sharp thing in your eye will hurt and usually results in spending a few hours in casualty.... wear some eye protection ( no, squinting or looking at what you are doing sideways doesn’t count as eye protection ) .

Cutting metal is also noisy ...... ear plugs :)
 
Step 1

Cover the panel in masking tape and mark out the position of the fan (or fans) mark the centre by drawing from corner to corner.

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Step 3

Draw out your circle. Probably a good idea to double check all you marking out at this point. When you’re happy with everything use the dividers to score through the masking tape and remove the tape from the part that’s going to be the hole.

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Step 4

With the Dremel make a shallow cut in the surface of the metal about 10mm from the edge of the circle, you aren’t trying to cut through just mark out a guide line.

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Step 5

Cut through the metal following your guide line. The Dremel will probably snag and jump while you are doing this but that’s why your guide line is back from the edge.

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Step 6

Cut around the circle again aiming to get to about 5mm from the edge of the circle. The Dremel should be easier to control now as the off cut is smaller / weaker and doesn’t cause the Dremel to snag as much.

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Step 7

Use the edge of the cutting disc grind / nibble back the cut edge until you are about 1>2mm from the edge of the circle. It’s worth taking your time with this for a couple of reasons, first if you slip now you’ll probably mark outside the hole. Second the closer and more even you get this bit the less you have to do in the next step.

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Step 8

Now the fun bit (not).... start filing. Not much to say about this bit apart from don’t file down to the line a bit at a time , rather keep working around the circle getting closer evenly , you’ll get a smoother circle this way . Keep going until you reach the edge or get fed up, whichever comes first. Then you’ll need to remove any burrs, just use the file at a shallow angle to remove any sharp bits, finish off with a bit of fine sandpaper.

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hyperst Some patience to do all that, i would have run out long before step 5 lol, but well done on the results, do you have a picture when all the panel is polished up by any chance?

No forgot to take the final picture after I had cleaned up :rolleyes:


EniGmA1981 Looks good man nice and tidy! Did you have any problem cutting/filing accross those louvres?

They are a bit fiddly , just have to be careful.


Orange Peel I used a hole saw. Cost around £5 and only required a small amount of filing to smooth the egdes. Perfect size every time

I think the hole saw would have made a mess of the louvres and I didn't have the right size but did have a bit of time and everything else ;)
 
Couldn't use a hole saw because of the louvres .

Before realising the louvers were in the way the cheapest 110 > 120mm hole cutter for steel I could find was about £30 > £40.

All the cheaper adjustable ones seemed to be for wood and plastic only , though I suspect they would be fine on aluminium .

Cost in dremel cutters .... about £4
 
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