Blow Hole Fan Hole Saw

M

MOZZ

Limp Gawd
Joined
Jan 12, 2006
Messages
255
Hello i was going to cut some blow holes to mount some fans and the mount the radiator to the fans, 120mm fans. I wasnt thinking and picked up a 4 3/4in hole saw. basically 121mm. Is this circle going to be too big for the fan? meaning if i cut it will the mounting holes to mount the fan be cut out as well? thanks
 
I bet if you do a bit of measuring, then make a drawing on some graph paper, you'll discover that you won't have a problem.

4.75 inches * 25.4 mm/inch == 120.65 mm, by the way.
 
its going to be close, escpecially after sanding. get a laser cut fan grill, there are many that are over-sized, this will cover any open area around the fan. there should be no problem with the screw holes, tho. you should still have a couple mm space.
 
I think the standard size people normally use for this is 4.5" - a little smaller than the opening, but almost perfect for the size of the fan blades.
 
It will be fine. It's the same one I use. Just make sure to measure twice as you have no room for error.

Fan grills help too.

Oh, and you get better airflow :D
 
Why not hold the saw up to a fan and see for yourself instead of starting a thread?

Go really slow and take breakes with that saw if your case is steel. Otherwise you'll ruin the saw.
 
thewhiteguy said:
Why not hold the saw up to a fan and see for yourself instead of starting a thread?

Go really slow and take breakes with that saw if your case is steel. Otherwise you'll ruin the saw.
Click to expand...

Well i bought the saw off ebay yesterday since it was alot cheaper there. Its a dewalt bi-metal saw. Locally they are around $30 it was new sealed on ebay for $10bucks. So i dont have it just yet to compare to any fans.

Thanks for the help guys :D
 
MOZZ said:
Well i bought the saw off ebay yesterday since it was alot cheaper there. Its a dewalt bi-metal saw. Locally they are around $30 it was new sealed on ebay for $10bucks. So i dont have it just yet to compare to any fans.

Thanks for the help guys :D
Click to expand...
Good deal. Glad to see you got the "Bi-Metal".

Now, whatever you do use SLOW to medium slow RPM's when using that big holesaw.
* The larger the diameter, the slower the RPM required *

Many people make the mistake of using high speeds & burn up their saw. If the chips start turning
blue you are creating too much heat. Back off on the RPM's. If you see sparks, forget it!
That is burning metal which is not a good idea.

Legion© said:
I think the standard size people normally use for this is 4.5" - a little smaller than the opening, but almost perfect for the size of the fan blades.
Click to expand...
^^^ - QFT

Many use a CD disk for a hole template - the perfect size for 120mm fan opening.
 
Thank god you bought a new saw. I attempted to use a used and bent one on a cordless drill. Went through 5 rechargable drill batteries to get 3/4 of the way through the hole. Had to tear it out the rest of the 1.4 with a pair of pliers.

Had a bit of sanding to do them, and some good ninja stars. :p

I have to say, the air flow got much better with just the 2 exhaust cut out. Soon, I will cut the intakes, and get some fan filters.
 
Actually, many like to cut their holes at 4 5/8" (4.675") since it more closely matches the diameter
of the fan blades. A CD/DVD disk makes an excellent template. ;)

dtess17 said:
So 4 1/2" is the best size for a 120mm blowhole?
Click to expand...
 
I guess it comes down to personal preference.

I use 4 1/2" for 120mm fans,3 1/2" for 92mm fans and 3" for 80mm fans.
The 4 3/4" holesaw (CD size) will show the fan frame in most cases, 4 5/8" will show the tiniest bit of frame either side.

Centre to centre (diagonally across the fan) the screw holes are 5 7/8" apart, so a 4 3/4" hole isn't going to be a problem for mounting the fan.

<edit> - don't forget you will probably still need to file/sand your hole a little to make it tidy and smooth, a slightly smaller hole leaves you a little more room for error.
 
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