Thar She Blows!

Thar She Blows!

I don’t know why beginning (and even some experienced) modders approach installing a blow hole with such trepidation (that’s fancy for “fear”). I think part of it involves the cutting of a perfect circle through metal. I’m sure it also doesn’t help that there are 6 ways from Saturday to do it. I’ve seen folks attempting or recommending every tool from a Dremel to a type of reciprocating saw referred to as a “saws all” (um…u no try pls thx). I appreciate originality and all, but sometimes a tried and true method is best - and that method would be the hole saw. It’s actually quite an easy mod to do with the right tools.

Oh, a little EULA first if you don’t mind:
Any safety reminders given herein are not to be taken as a substitute for proper training and, if required, supervision. You (the reader) are solely responsible for any outcome, positive or negative, resulting from use of this information.

Now, let’s get to the hole cutting business! I’m only going to cover making the hole in this post so I can give a bit more detail. I’ll get to mounting the fan and my patented (not really) 8-hole mounting technique next time. You will need some easy to acquire tools for making the hole cut:

  • Variable speed drill (preferably a cordless type)
  • Permanent marker
  • Masking, drafting, or painter’s tape
  • Hole saw with bit/arbor/jig (if required)
  • Eye Protection
  • Measuring device (a ruler will work, a square is better).

You can get all of these at your local DIY home center and they can be used for many projects of the modding kind (computer or otherwise). Real tool talk deserves its own exclusive post at some later date, but I do need to address the hole saw mentioned here - in case you’re running out to buy one.

You want to make sure the hole saw is the right size. Fans are often measured in millimeters (and to the outside of the casing) and holes saws are often measured in a far superior form of measurement - the inch. Here’s a handy table for convertin’ fan size to proper hole saw size:

50mm = 2.25”
80mm = 3.0” (3 1/8” if you can find it)
92mm = 3.5”
120mm= 4.5” (4 5/8” may also work)

Most important, make sure that the saw you buy or use is labeled “multi-purpose” or “for metal and wood”. Bi-metal saws are best. Some hole saws are only made for wood – you don’t want to use those. You also want to do a bit of research. Hole saws are all of similar design, however, some are far better in quality of materials than others. Further, the arbor and bit (sometimes called a jig) are typically interchangeable among different hole saw sizes – but only within the same brand and series! That means, you will want to stick with a brand – it will save you money in the long run. I’m not going to recommend a brand, but I will say that I use Lenox and am happy with them, and you should expect to pay more than $10 USD for the size we are using here (meaning that the one you’re looking at for $3.99 right now is not the one you want - heh).

Once you have your tools ready, pull the components out of your case (or the part of the case you are going to cut if it’s removable). Cutting a hole into a fully assembled computer is asking for damage. With the case empty, find where you want to put your hole and measure off to mark the center. Keep in mind that components will eventually be in the case. If the hole is on top, for example, make sure you will have room to install the fan while both a PSU and a top bay mounted optical drive are in it. Once you have the center spot marked, you will want to put tape anyplace the blade of the hole saw will cut through. This will minimize any scratching if you slip. Finally, make sure the case is secured somehow and won’t move while you are drilling/cutting. Put on your safety glasses!



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I did basically the same thing a while back but used a normal drill bit and a metal nibbler. Using an old fan grill for an 80MM fan, I penciled in the outline for the main hole and for the screws to hold the fan in place. Since the nibbler only eats like 1mm x 3mm rectangle of metal it took a while. And was definitely not as smooth as the hole saw, but also was not as loud and screechy as the hole saw would be.

It was for a water cooled system. I figured I would put the radiator at the top of the case inside. Worked pretty well except for the cheap water pump I used died pretty quickly with having to pump coolant above its position in the case. Too much pump head I guess.

Anyways, just trying to say that there are more ways to skin a cat then just the hole saw (wouldnt that be a great you tube video, [imagines high pitch cat whine masked by drill motor sound]).



I assume you took uninstalled the MB and all components to avoid getting metal shavings inside everything. I would also recommend reinforcing the top of the case with a block of wood from underneath to prevent the metal from flexing and chipping paint or leaving any creases or dents.



I devoted at least two sentences to removing the parts from the case - All of them. A single shaving can actually kill a mother board!

I'll make that more clear next week.

The wood might help a first timer, but if you let the saw do the work as I said, you should have no warping on a standard quality case. There is no need to "push".




I see that info now. I must have skipped past that. Thanks.



If I wanted to cut a hole in plexi-glass, can I use the same drill piece? How would I put enough pressure on the plexi-glass to cut it without cracking it?



You can use the same technique on plexi. A carbide hole saw would be better though - but bi-metal works fine. Some tips: Remove the plexi from the case. If it's new plexi, leave the protective covering on it - but still use the tape where the hole will be cut. If there is no covering on it, use tape - drafter's tape is best.

Cracking comes from flexing the poly. To stop this, clamp the piece to a piece of plywood (or similar). Place butcher paper (or gift wrap) between the wood and plexi. Use clamps with rubber or soft contacts (or improvise with a piece of thick cloth). Plexi damages easily. You don't want the piece to become a helicopter while you're cutting either - so clamp the whole thing to something stable. Remember, the pilot bit will drill all the way through - make sure there is nothing important under the wood.
Arf - safety alert! Refer to the "EULA" statement made in the blog entry. While this stuff is pretty simple, those under 18 require adult approval (and supervision)and no-one should work with power tools without another person aware of what they are doing and in the vicinity.

When you make the cut, do it in a few "passes". Cut a bit and back out and wait a minute. Then repeat until you are through the plexi. Do not let the saw stop while in contact with the plexi. You are trying to avoid melting the plexi during the cut (and melting it to the saw as well).

You don't need to cut the hole through the wood.

Leave the plexi on the wood (or put it back on the wood) for drilling mounting holes.

Lastly, you can finish the edges of the hole with fine grit (800-1200) sand paper - or get fancy and flame polish it (buy health insurance for that one!)

Hope that helps!


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