Cutting fan holes / Guide to Hole Saws

Grez

Well, I've answered questions about cutting fan holes about ninety thousand times now (and honestly, never resented it), so I figured it was time to create a general how-to on the process and, along with it, give a quick run-down on hole saws. So, here we go...

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CUTTING FAN HOLES

Beyond putting a fan in an entirely new location, there are advantages to cutting out pre-punched case fan grills. By cutting a new hole in the case and replacing the pre-punched grill with a wire or more open-mesh grill, you accomplish three things:

1. You increase airflow in the case (by as much as 33% if the pre-punch is fairly small),
2. You decrease the noise level of the moving air being forced through the grill, and
3. You reduce backpressure on your fans, which theoretically increase their life span.

In any case, whether you are cutting a fan hole for aesthetic reasons, performance, or both, it is one of the most common custom case mods done in the modding community, and one of the most often-botched.

First of all, unless you have no other choice, do not use a rotary tool or nibbler to cut your fan hole. You will inevitably end up with a sloppy, lop-sided hole that will take you about five-to-ten times longer to cut than by using my suggested hole saw methodology. While I realize that there are a couple of guys around the forums who actually have the skills to cut a nice, round fan hole with a rotary tool (and I do not include myself in this group), they are the exception to the rule. If you’re not absolutely certain that I’m talking about you, then I’m not. For the other 99.9% of us, using a hole saw is the solution to the problem.

A quick list of tools you’re going to want:

1) Safety glasses
2) A good work surface
3) Clamps
4) A good power drill
5) Hole saw(s) and arbor/mandrill
6) Half-round file (aka “bastard”)
7) Scrap wood

What is a hole saw?

I fully realize that most of you are aware of what hole saws are, along with the general application. If this is you, then go ahead and skip to the next section, Choosing a Hole Saw. However, for the new guys (or gals), I think it’s good if we give a full explanation here.



A hole saw is a hollow, cylindrical hunk of metal with directional teeth along one end. It’s intended to be attached, along with an arbor (a clamp with a drill bit in the center of it, also called a mandrill), to a power drill or drill press. The drill spins the hole saw very quickly, and thus cuts a perfect circle into the surface of the object upon which you’re working. The drill bit is there in order to get an initial grip on the material and keep the hole saw centered during cutting, which keeps it from skipping across a hard surface or getting “wobble,” which in turn would produce an uneven hole.

Also, you can check out this hole saw wiki.


Choosing a Hole Saw

The most obvious factor in choosing a hole saw to make your cut is the size. This is easy to outline, since there are three common sizes of case fans: 80mm, 92mm, and 120mm. Each size of fan has, of course, an applicable size of hole saw. Here is an easy guide to choosing your hole saw size:

80mm = 3” hole saw
92mm = 3.5” hole saw
120mm = 4.5” hole saw

Believe it or not, beyond the size itself, there are two other major factors in selecting a hole saw(s): material type and arbor/mandrill type.

Hole saws are generally available in three material types: standard steel, carbide, and bi-metal. For case modding, you want to avoid standard hole saws altogether. These will wear out in mere seconds when used on a steel case. Carbide saws last a long time (and are very expensive), but are actually intended for use with softer materials. That leaves us with (you guessed it) bi-metal hole saws, which are what you want for case modding. Let me repeat this to make it clear (this is very important): always use a bi-metal hole saw for case modding! They are hard enough to cut through relatively thick steel without going blunt, and standard steel cases shouldn’t provide much of a challenge at all when the hole saw is coupled with a powerful drill (more on this later).

There is always some debate about arbor/mandrill type. Hole saws can come with a permanent, pre-installed arbor or, more commonly, as a stand-alone saw where you need to buy a separate arbor. Many people prefer the first kind, as it is usually a little cheaper than buying a separate saw and arbor. However, this has the following drawback: if you accidentally snap the drill bit in the center of the arbor, your hole saw is now useless. This is why I prefer the separate arbor solution. The separate arbor/mandrill is usually adjustable, and you can buy a quick-release variety and doesn’t require tools to switch out your hole saws (this is what I have, and it saves lots of time). Since you can adjust the height of the bit, you can decide how much “lead” you want to have when drilling your pilot hole before the hole saw grabs and starts the actual cut. Additionally, you can usually change out the drill bit itself on this type of arbor/mandrill, so you can put in your own metal bit, or whatever is applicable. Either of these choices is fine, and it’s really up to personally preference. Also, when choosing your arbor/mandrill, pay attention to the size of the peg that will go into your power drill, and make sure it is compatible with the drill. I have a big 1/2” mandrill, and this won’t work with medium-sized drills, which often can only handle up to 3/8”. So, just be sure to check before you buy.


Cutting the Hole

Before you begin chopping away, another thing to check is the quality of your power drill. The first time I attempted to cut a fan hole, I was using a Black-and-Decker 1000-series hand drill, which is basically intended for light home use. I almost smoked the motor on it, and all I had to show for it was a somewhat shiny ring of bare metal on the top of my case – I wasn’t even halfway through the metal. You need to be sure you have a good, powerful drill. My personal drill now is a 7.5 amp Milwaukee hammer drill (which has so much torque it will practically rip your arm out of the shoulder socket if it binds up on you), but you don’t need anything quite that extreme. Any good, solid drill with at least three or four amps of power should do the trick. If you’re going the drill press route, almost any drill press that’s not a complete toy should do the job just fine.

Now that we’ve made all of our selections, cutting the hole is really the easy part. There are a couple of safety measures that you should always take:

1) Wear safety glasses! You’re going to have raging hot shards of metal (or acrylic, I suppose) flying around the room! You don’t want this stuff in your eyes.
2) Clamp your object to be cut securely. Have a good work surface (even it it’s a couple of saw horses and some plywood). You don’t want your high-torque power drill to shoot a sharp-edged, three-pound sheet of steel at you. Besides, if you don’t clamp things down properly, you’ll get vibration and your cut will turn out messy.

At this point, you just need to measure to find your center point for the cut and mark it. This is often really easy if you have a pre-punched fan grill you’re cutting out, as they will frequently have a center hole already there. Now, you just line up the tip of your arbor on your marked center point and begin to drill, using just a reasonable amount of downward force. Don’t push too hard and bend your metal (or crack acrylic!); let the drill do the work. I like to get the drill bit through, let the drill spin down, and then reposition my hole saw so that the blade is about 1/8” about the surface, then spin the drill back up. This way, I know that my initial touch will be as flat and even as possible. When cutting, you want to keep the pressure as even as possible across the surface of the hole saw, so try to keep the drill as perpendicular to your cutting surface as possible.

When cutting metal, you want to spin the hole saw fairly quickly. With a good saw/drill combination, it will take less than 10 seconds to punch through the standard thin steel case panel (with my Milwaukee, it usually only takes 2-5 seconds). When cutting/drilling acrylic, take your time. You want to spin the saw/drill at lower RPMs then to be sure that you don’t bind up and crack the acrylic. Have patience…it will pay off.

It’s also a good idea to clamp some scrap wood behind of the surface you’re cutting through. This way, when the hole saw punches through, metal won’t bend and acrylic won’t “bullethole” outward.


Cleaning Up Your Cut

Ok, so now you have this nice, perfect hole cut in your case. What’s next? Well, if you just cut a metal surface and you don’t like blood shooting from cuts caused by razor-sharp metal, it’s a good idea to clean up your cut.

The most common method of cleaning up the hole you’ve just cut is to use the half-round file, aka “bastard.” Using the round side, spend some time filing across the edge of the hole from both sides of the hole. This will eventually wear the sharp edges from the cut down to a nice, smooth surface. It may take a few minutes, so be patient. If you’ve just cut out a pre-punched case grill, this will probably take extra time, as you may have lots of “jaggies” left over from the grill pattern.

Another way to clean up the cut is to use a light grinder or (my preference) a sanding cylinder on a rotary tool. You should run this at a low-to-medium setting so that you don’t grind away too much metal and create uneven spots in your circle. Work against the rotation of the grinder/sander so that it doesn’t skip around on you.


Drilling the Screw Holes

Now that you have a fan hole, you need a way to mount the fan. Fortunately, this is probably the very easiest part. Just take your new fan grill (or even the fan itself) and center it over your newly-cut hole. Once it’s positioned perfectly, make marks with a pencil through the screw holes in the grill. Now, all you have to do is drill out the marked spots on the case.

Again, when drilling, take safety precautions. Don’t get lazy. Thousands of shop teachers missing fingers can’t be wrong.

It’s a good idea to clamp a scrap piece of wood behind the surface again, as this will prevent the “bullethole” effect of the drill finally punching through the surface. Be especially careful when drilling acrylic and take your time.

When you’re done making the screw holes, you may need to clean them up a bit as well to reduce sharpness (if you’ve been drilling through metal). Here’s where your file comes in handy again. Most half-round files have a short, thin bar on one end that starts about 1/8” thick and goes up to 1/4” or 3/8” (depending upon the size of the file). Just cram that puppy into each of the screw holes (I know, I know, there are about a million jokes there…try to resist) and twist it around. The tempered metal of the file is stronger than the case panel, so it will remove any loose pieces of metal and help dull the sharp edges.


Dressing Up the Fan Hole

Now you’re almost ready to mount your fan and new grill. In fact, you could just go ahead and do it. But, things will look a lot nicer if you dress up the fan hole a bit.

One of the best ways to dress up the new fan hole is to put “c-channel” around it. This is essentially a long strip of rubber or plastic that has a hollow pit in it, so that when you look at it in cross section, it resembles the letter “C”. It can easily be cut to length, so you can just wind it around your fan hole, and where it meets itself, cut it with a sharp knife or scissors, and you magically have a professional-looking fan hole. You can usually find the stuff in black and chrome. Truck door-edge molding from the auto parts store works pretty well too.

The rubber c-channel also gives you the added benefit of essentially working as a fan vibration dampener, and will help keep higher RPM fans from vibrating the larger metal panels. Trust me, as a guy whose main rig is in a server case, this can be annoying unless you dampen things properly. By using this method, you avoid having to buy the actual fan vibration dampeners (square rubber brackets that wrap around one side of case fans).

C-Channel pictures:
http://www.pccasegear.com/images/fanholesm.jpg
http://www.bestbyte.net/merchant/mer...gory_Code=CACM

You can sometimes find c-channel at Xoxide.com. Always shop there first (of course!), but if they’re out, another good vendor is Bestbyteinc.com. They’re local to the Houston area, and I’ve dealt with them personally several times. They’re honest, cheap, and provide good customer service.


You’re Done!

So now you’re finished! So mount that fan and any grills/filters/lighted bolts/etc that you want to! Then sit back and enjoy your professional-quality mod (enjoying a quality beer while you do this always enhances the experience).

Good luck, modders…

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A final note: in addition to hole saws, another option is the adjustable cutter paired with a drill press. I generally recommend the hole saws because most people actually own or at least have access to a good power drill, whereas many people do not have access to a drill press. But the adjustable cutter works just as well, and you only need one for all fan sizes, which is its advantage. If you’d like to know about adjustable cutters, ask Xox Forums’ own R. Carter, who uses these on a regular basis on his impressive mods.

xtremegamer_624

Nice guide, very informative on a good way to cut a hole for any mod....No dremel?

I would like to get a hole saw attachment one day though, and make it much easier. Now I'll know which size to go with for which fan. Thanks for that.

Grez

NP, bro. And see? You knew that I was talking about you. But for the other 99%, as I said...

Blue Fox

Nice guide, will come in handy for me since I may soon be cutting some fan holes in my case, but I DID already have a bi-metal hole saw, I just have a hard time finding ones that are just the right diameter.

thegrimone

Thanks Grez, I get sick of seeing threads about this very thing, and so many people not using the search.

R.Carter

Thanks for the props, and the awesome guide.

About the adjustable circle cutter. Props must really go to Tech-Daddy, who is where I heard about these beauts from.

Here is what we are talking about:



For me, the only way to cut a round hole is with the adjustable circle cutter. Like Grez said, you only need one. Mine goes from 1"-6". That will cover up to a 15cm fan! At a cost of less than $20. You can get a nice little bench top drill press for about $80ish from Lowe's or Home Depot. Maybe even less at Northern Hydraulic on the right day. At $100, that is still cheaper than a drill and a full set of bi-metal saws. Of course you can't use your drill press around the house doing your chores, but WTF...

The other advantage to using a circle cutter is there is little or no filing required after cutting. I don't know about you, but I am not a fan of filing. The cuts made with an ACC are very clean. They are extremely sharp though, so filing is a must if the hole has any exposure.

As for getting yourself your own ACC, the only place I have found them is Ace Hardware. They are made by General Tools. Here is a link to the tool on the General site: General Tools

Getting extra cutting bits may be difficult. But your local Ace can get them.

FETUS

Any tips for cutting slots if you don't want a huge hole you need a cover for?

Grez

No problem, you deserve it.

Well, then props to him. He's one bad modder.

Then stick with Ace we shall. I've found these in the online catalogs for both Home Depot and Lowe's, but in both cases they don't seem to be as heavy-duty as the one you use. They both specifically note that the only materials they are approved for are things like wood, plastic, etc., i.e, relatively soft materials. I'm thinking that they wouldn't work too well on the metal. I may take a look at one of these for giggles at Ace just to get a good visual comparison, and see if I can perceive any noticeable difference in density or strength. Thanks for the heads-up.

travis712

Hey man very nice guide. Will help a lot of the newer people to the site. I'll be putting a new fan hole in a piece of plexiglass i'll be using for my window(replacing old, scratched POS piece). Just checked for a 3" hole saw that I thought my dad had but no luck, guess i'll hafto pick one up tomorrow.

naggledown

WOW thats all i have to say. Ive been doing it the hard way with a dremal. I get good holes but still really freeging hard thx for this one

naggledown

if you are cutting plexi glass plz plz put some wood behind it if you don't you will be sry
trust me i didn't and i split right in half

Glowing_The_Smurf

Thanks for the info Grez. I've been wanting to cut a hole in my case for a 120mm fan, but I didn't know which sizes to use or which material the saw should be made of. And thank you R. Carter for the info on where to buy teh ACC. (Runs off to ACE)

Grez

You're welcome.
Yep, the good one that I found was at Ace. But you can sometimes find them at the big home improvement stores, too.

jesusXchrist

nice job, again! ure links to C-channel are dead btw, and i wish you posted some pics of your work, cause i have some trouble with the clamps and where to drill down, in other words... the position of my acrylic and what im drilling down on

Grez

Thanks! Fixed!

Ryanaven

What would you recommend for a 140mm or a 250mm hole? I'm having a lot of trouble trying to find something that will meet my requirements. The case I purchased came with a 360mm window fan, but I took it out and bought a 250mm to replace it (not to mention a new peice of acrylic) , and a 140mm to replace the dinky 80mm blowhole. Any options will greatly help,
Ryanaven

Wolvenmoon

Well, a 140MM hole you should be able to find a holesaw for. The 250MM fan is about 9.88 inches, which suggests a nine inch holesaw-way too much for most consumer drill presses (I'm guessing)

You'd be better off getting two 140MM fans instead of the 250MM, unless you *HAVE* to have the big fan, then all I can think of is a dremmel or someone with a very well equipped shop.

Edit: 140MM converts to 5.5 inches which suggests a 5 inch holesaw, not too horrible. Also, dremmeling a 250MM hole is a huge project, I wouldn't even think about it.

Jodah

awesome Tut Grez. what about knockout punches for? such as what mnpctech uses? i know the 120mm one he has is like 500 bucks, but the smaller ones shouldn't be too expensive. couorse, perhaps those are for guys that do it 24/7?

Grez

Thanks, man. Yeah, knockout punches are awesome, but most people either don't have access to them or can't afford them. And the power drill/hole saw combo is very effective and totally affordable, so I usually just stick with that recommendation. But by all means, if you have a shop with badass tools like knockout punches, go for it, bro!

Wolvenmoon

A quick google checkout scan says even the small ones are hugely expensive..out of curiosity, how do they work?