Best way to make very large hole in cabinet

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MrAl
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Re: Best way to make very large hole in cabinet

Post by MrAl » Sun Jan 17, 2010 2:02 pm

Hi again Janitor,


Yeah hehe, that is from a program i wrote a while back to calculate the windings of a toroid
core inductor. That is the cross section view of the finished toroid center and the circles are the
cross section of the wire itself. I thought it would look something like that anyway :-)

You say one half inch holes? Well that would be nice yes, but that is not as easy as it
sounds to drill into very thin sheet metal. It requires first say a 1/16 inch hole, then
widen that to 1/8 inch, then maybe 1/4, then 3/8, then 1/2 inch. That's still quite a bit
of drilling dont you think?
Still, i guess it is an option i'll have to think about.
LEDs vs Bulbs, LEDs are winning.

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Janitor Tzap
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Re: Best way to make very large hole in cabinet

Post by Janitor Tzap » Sun Jan 17, 2010 4:58 pm

MrAl wrote:Hi again Janitor,


Yeah hehe, that is from a program i wrote a while back to calculate the windings of a toroid
core inductor. That is the cross section view of the finished toroid center and the circles are the
cross section of the wire itself. I thought it would look something like that anyway :-)

You say one half inch holes? Well that would be nice yes, but that is not as easy as it
sounds to drill into very thin sheet metal. It requires first say a 1/16 inch hole, then
widen that to 1/8 inch, then maybe 1/4, then 3/8, then 1/2 inch. That's still quite a bit
of drilling dont you think?
Ok, scratch off this idea.
{I keep forgetting about not restricting the air flow through the case.}

Here's some more information about cooling you might like to look at.
http://www-03.ibm.com/procurement/prowe ... ciency.pdf


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MrAl
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Re: Best way to make very large hole in cabinet

Post by MrAl » Sun Jan 17, 2010 5:59 pm

Hi again,


Gee for a minute there i though i was getting carried away he he :smile:
After reading that i realized i have to call my power company and insist on
them installing three phase power to my house so i can properly cool my
PC computer case (he he he).

Interesting though, i was against holes from the beginning, but was willing
to go with that if it seemed a lot easier. I wanted to minimize blockage to
the max too.
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Re: Best way to make very large hole in cabinet

Post by Robert Reed » Sun Jan 17, 2010 8:58 pm

There is only one drill bit I would consider for sheet metal and that is the SPUR BIT, sometimes referred to as sheet metal drills. These cut a clean hole rapidly and with very little jaggedness on the edges. They come in sizes ranging upwards of 3/4" and are commonly available. You could drill a circular pattern inside the perimeter and finish up with a hand nibbler between holes. In the time frame this post has run, you could have drilled a 1000 cases :smile: However, I may have missed one point and that is - does the hole show or is it hidden by the fan frame? One other point about this method is that it is MUCH easier to do with a floor mount than by hand, but again with proper backup, the hand drill isn't too hard to use.

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jwax
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Re: Best way to make very large hole in cabinet

Post by jwax » Mon Jan 18, 2010 3:57 am

MrAl, have you considered liquid cooling? :smile:
Or if you still want holes, use a Unibit. They drill sheet steel clean and burr-free:
http://www.amazon.com/Irwin-Industrial- ... B00126KYXO
Also, a rotary rasp or sanding drum, 1 or 2" diameter, will quickly smooth out the peaks after drilling the perimeter holes.
I agree though, that a jig saw with a metal-cutting blade would be best.
If you want pretty, there is a plastic edging that is made to cover sharp, rough-cut edges, but I don't recall what it's called. "Tubing with a longitudinal slit"?

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MrAl
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Re: Best way to make very large hole in cabinet

Post by MrAl » Mon Jan 18, 2010 7:46 am

Hi again,

Robert:
Well i would like to find a method which i can use on other cases too, or to do
more than one fan on this case, so i dont mind taking a little time to consider
various techniques.
The hole edge should be mostly hidden by the fan frame so i guess it doesnt have to
be perfect.
Maybe i am taking a bit longer time with this so i dont actually have to do anything
yet :smile: While thinking about it i dont have to drill or cut anything :smile:
Seriously though, i want to get it at least mostly right the first time because once
it is cut that's it, the panel could be ruined. I guess i could always bolt some sheet
metal over the hole though and make a new hole in that, but that gets to be a bit
much too if you know what i mean. I was hoping for simple yet effective.

John:
Yes i have thought about liquid cooling, but i feel that it is more than what i want
to get into at least right now.
I have a Dremel tool with cutters, including diamond cutters but i have read they might
not be that good for steel anyway (but then i dont know for sure yet).
Oh yeah, i know about that edging. I might get some or just not worry about the edge
that much as the fan should cover most of it at least on the outside (fan is going to
be mounted on the outside not inside).
Wow, 30 bucks for that bit? That's a bit much isnt it (he he)?
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Re: Best way to make very large hole in cabinet

Post by Bear » Mon Jan 18, 2010 2:53 pm

Mr.AL...Yes I have used it before. If you are interested I can tell you how to do it. I have used routers to cut .032" ferrous up to .250" alum. material. You have to make multiple downward cuts & use kerosene or steelwool as a lubricant. Everybody tries to kill it in one pass. The secret is to make multiple passes. A nice sharp .250"dia. flat bottom carbide router cutter would work fine. Backup the the material with .375" plywood and using flat head screws anchor the portion to cutout to the plywood(must be flathead screws so that the circle cutter attachment will not get hung up on the screws as you go around.) Next, use the mounting holes for the fan to anchor the other portion of the case to the plywood(again using flathead screws.) You can actually dimple(extrude) these holes using a ball bearing after drilling the fan mounting clearance holes. If you dimple the holes, you can then flatten them back to their original shape after you are through. When screwing down the part to the plywood backer, do the inside circle first and the go to the outside next so as to keep the parts as flat as possible. You can always clean off the kerosene with mineral spirits immediately after finishing so the kerosene does not permeate the paint with oil. Since this part is most likely painted I would not use the steelwool trick as it has a tendency to scratch surrounding surfaces. Again, make multiple passes!!!

Take care all

Dennis

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MrAl
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Re: Best way to make very large hole in cabinet

Post by MrAl » Mon Jan 18, 2010 4:26 pm

Hi Bear,


Hey that's a pretty interesting idea too. Something else i have to think about now then :smile:

There is one problem though, in that i dont own a router anymore. I had one back when but
not sure where it went. I would buy one but i would never use it for anything else, and i guess
if i do end up buying something i would want to be able to use it for other things too.

You know what is a shame is that i can not use my "Multitool". That's the tool that vibrates rather
than rotates and makes nice cuts in things. Trouble is it would never work on something this thin
and i dont think it has a metal cutting blade either. It has a diamond blade, but that doesnt cut
into things the way you would think it should...i tried it. It just makes scratches on the surface.
Too bad.
As i was saying though, i do have a Dremel and i have a feeling i am going to end up using that
after all so i dont have to buy anything. I have a multitude of cutters for it too. I have done
complex shapes in plexiglass before so i have an idea how it would go. Would take a bit longer
but what the heck, right? I have read on the web and someone else mentioned drilling a set
of holes in a circle (not too many) and then cutting between holes to remove the entire 120mm
part of the panel. I think that is going to end up being my first attempt.
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Re: Best way to make very large hole in cabinet

Post by Robert Reed » Mon Jan 18, 2010 5:28 pm

One other thing I almost forgot about since I have not used this method for a while and that will bring us back to the jig saw. Actually, Bears reply of router attachment circle cutters got me to thinking about it. I used the same setup with my jig saw. It is very easy to throw together with a scrap of 1/4" plywood. Only requires one hole in the center of the knockout circle (And of course one starter hole to insert the blade).. As I remember the method was quite stable with a smooth cut. But regardless of how you end up doing it, do you have a piece of scrap sheet metal around for practice?

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Re: Best way to make very large hole in cabinet

Post by MrAl » Tue Jan 19, 2010 5:37 am

Hi Robert,


That sounds like another interesting idea, but do you think it would be practical for a hole only 120mm
in diameter? The radius is less than 2 and a half inches (actually about 2.4 inches). The larger fans
250mm diameter might be ok for this method though.
I also seem to remember using jigsaws in the past, and doest the blade vary a bit side to side so that
it is difficult to get a 'straight' cut? It's been quite a few years since i've used one now :smile:
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Re: Best way to make very large hole in cabinet

Post by Robert Reed » Tue Jan 19, 2010 8:30 am

I do a lot of woodworking and some metal working. The general idea is to cut about 1/16" from the intended opening and then clean out with whatever (file,Emory,etc.) right to the line. This allows some leeway for a wandering blade to stay inside and on the 'scrap' side of the cut when cutting freehand. The blade won't wander much on a curved cut with thin materials but over 1/8' thick it will.The circle cutter attachment locks the saw into a rigid cut and will follow the line exactly. I always use a high quality blade such as Bosch and with a very fine tooth arrangement. These are not expensive - $2 or so. In "must be right the first time" applications such as yours, I always test the setup on scrap material first.

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THAR' SHE BLOWS!

Post by MrAl » Tue Jan 19, 2010 11:18 am

THAR' SHE BLOWS! :smile:

Hi Robert,

As the title suggests, i got in the mood to try this and didnt feel like going to purchase a
jig saw just yet (although that's next on the list) so i drilled 16 holes in a circle and cut
between them with the Dremel. Came out ok i guess, picture attached. Needless to say
the blow hole is there now and the 120mm fan seems to be working pretty well. The
four green LEDs light up the whole back of the computer so it's quite amusing :smile:

At first i used the smaller diamond disk, but the larger composite/reinforced disk seemed
to work faster so i used that. It was a little tricky making the template, making some fine
measurements, but it turned out good enough. It would have probably been better to do
that on the computer and print it out, but i went the old fashioned route.

One thing i realized is when i took off the 80mm fan that was just above that fan hole
i realized that the holes in the panel are very small, and are blocking at least 2/3 of the
hole for that smaller fan. So, that's next. It's smaller but it needs cutting out too.

I also realized that there is quite a bit of fine dust after cutting with the Dremel, so i
would rather go with the jigsaw next time. That will make particles that are a bit
nicer to deal with. The panel had to be washed very good after cutting.

Im not sure how well a circle cutting thing would work though for these small fans
like 120mm. Any ideas on that? The radius is very small. I dont think it would be
too hard to follow a circular line though, i could do that with the saw. That brings
us to the next question...

Do you think a cheapie 30 dollar (USD) jig saw would be good enough? I dont want to
have to spend a fortune on this of course. I can get blades for about 5 dollars for three.
Also, do the blades break very much? It's been quite a while since i used one of these
and i dont know how cheap they are making them now either.

This is a picture of the piece that came out of the hole. I covered it in Saran wrap so
it would not scratch up the scanner glass. As can be seen at the lower left corner
i slipped once with the Dremel, but it didnt hurt anything. I didnt want to try to get
the hole big panel on the scanner so i scanned the hole piece that came out instead.
As can also be seen is that it came out almost a true circle, so 16 holes seem to be
plenty for this diameter fan. I was going to try to get away with 8, but there would
have been some areas a little too restricting so i went with 16. They dont take long
to drill at all even with a hand drill. It's harder to cut between them with the Dremel
but i guess a little patience goes a long way, as long as you are willing to put up with
the noise it makes as it really is quite loud when cutting with the disk.
I'd say it took about a half hour to make the template, then about 15 minutes to
drill the holes, then about 30 minutes to cut between the holes.

Image
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Re: Best way to make very large hole in cabinet

Post by Janitor Tzap » Tue Jan 19, 2010 12:42 pm

MrAl,

Who cares what the cut out looks like. :lol:

We want a picture of the case with the fan mounted in it.
{So we can critique your work!} :lol:


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Re: Best way to make very large hole in cabinet

Post by Robert Reed » Tue Jan 19, 2010 12:50 pm

Well it certaintly looks OK. As you can deduce from all the replys you have received, there are a myriad of ways to do this. Depending on ones available tools and experience in using them, there is no best choice for any one of us individually. Just however we have been successful in the past and feel comfortable with. BTW, what are all those dimples or whatever on the waste piece?

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Re: Best way to make very large hole in cabinet

Post by jwax » Tue Jan 19, 2010 1:48 pm

Makes me wish I still had access to a CO2 laser cutter. Could have saved many pages of forum space, but we've heard some great ideas here! :grin:
I agree- let's see a pic of the finished unit MrAl!

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