24. HOW *NOT* TO DRILL AN ARRAY OF HOLES FOR PSU INTAKE
It was bound to happen, a screw-up that I couldn't easily recover from. Luckily, it's in a place where most people won't see it, and there are some things I can do to fix it later, but I frankly don't have the desire to mess with it further at the moment.
So here's the offending piece:
What's the problem? Uh oh, well wayyy back at the beginning, I flipped the Mobo and PSU so that the PSU would be on the bottom. And this case was old enough that it only expected PSUs to mount such that they draw air from inside the case and exhaust it out the back (in fact, originally, the PSU fan was the ONLY "case fan" for air flow).
But newer cases (as in this decade) typically have the option to draw fresh air from the bottom of the case, and exhaust it out the back of the PSU, so the PSU gets cool air, and its air flow is independent of the rest of the case. I want that functionality. But unfortunately, I forgot about it until now. Better take care of that before I go painting the bottom panel, right?
Unfortunately, before I could take that step, I had another small problem:
This case was not designed for the PSU to be flipped "upside down" with respect to the panel opening. So there's some obstruction. Let's get that out of the way with the trusty dremel:
Now for problem area #2. The screw holes don't line up.
Two of the PSU holes are out in the open air. Not much I can do about that at the moment. I'll need (at some point) to add a backer plate to the back panel and redrill holes. But honestly, with the PSU on the bottom, those two aren't a huge concern.
The two bottom holes, however, I can address by making a stencil and drilling holes in the back panel.
So first, let's attach a piece of cardstock to the back of the PSU, trace out the shape of the PSU, and punch holes where the screws should go:
And then we stick that on the back of the back panel, and transfer the hole locations to the back panel and drill out the holes. I used a 3/16" bit:
Well that all seems to have gone rather well. Now I can use a similar method to figure out where the PSU vent hole(s) should be. First step, I need a hole template, which MNPCTech kindly has available online.
Cut out the hole, center it over the PSU intake, and tape it down. Cut off some (but not all) of the excess cardstock that overhangs the side and back. Cut the front of the cardstock flush with the PSU.
Then I mounted that to the back panel using the nice screw holes I just finished drilling.
Doesn't that look nice?
Then I attached the bottom panel to that assembly. It more or less just snapped into place (which bodes well for later actual assembly). I could then tape the stencil to the bottom panel:
Carefully removing the PSU/Backpanel, I was left with the location of the vent transferred onto the bottom panel and drew some lines through the center of the circle so I'd have some guides to work with.
Now... here's where things started to go wrong. Take a closer look at that bottom panel and the vent location:
Notice that the PSU is not centered on the bottom panel, so the vent isn't centered. Further, it's a 140mm hole, and I don't have a hole saw that size. To make matters worse, the hole overlaps the "legs" for the bottom panel. I can't just cut a 140mm hole even if I did have a hole saw that size.
Now, I considered cutting a "window" for the bottom vent at this point. Basically it would be partially a circle, but would skate around the bottom panel "legs" area. The problem with that is I was starting to become concerned with the structural integrity of the bottom panel. It's not exactly the thickest material, and already has flex to it. Cutting out a big hole right next to where the weight of the case will be resting seemed a bad idea.
So, I reasoned, I would do a "swiss cheese" pattern of holes, following the lines that I had cut. It is at this point I wish I'd had this advice already:
Originally Posted by animal0307
Next time you want to drill an array of holes like that make sure you have a new sharp bit with the easy start tip. Also practice on a block of wood and if you make it out of a nice hard piece of wood and you can use it as template for the real thing.
Yeah... things didn't quite go well.
First off, since the vent area isn't centered, trying to follow the "hole" pattern will result in a set of holes that won't be centered on the bottom, and may run out of room in different spots. And that's exactly what happened. Secondly, I used the wrong bit, and tried to use one that was too large. It had a tendency to "walk" on me, offsetting the holes by up to 1/16" (which really shows in an array of holes):
Finally, because of all those problems, when I was done with the 1/2" bit, I felt I didn't have enough venting, and tried to fill in with a 3/8" bit. And that just made it worse from a symmetry standpoint. The end result was less than stellar:
Note the off-center holes (1), the 3/8" holes (2) and spots where because of various issues I couldn't fit a hole where one should have gone (3).
Overall, I think I have plenty of venting for the PSU intake, but frankly I was very unhappy with the resulting aesthetics. (That's putting it mildly. There was a lot of swearing, followed by the imbibing of alcohol.)
But overall, if I was going to learn that lesson, this was the place to learn it. The final result won't be visible to the casual viewer of the case once the PSU is mounted:
1) Don't try to do array's of holes if at all possible.... lol. If I had to do it over, I would probably have cut a window and epoxied a stiff grill/mesh on the bottom for stability.
2) If you must, take animal0307's advice. Use the right bits, and practice on wood (and then metal) first.
3) Drill your holes from the center outward so that any errors are on the outer edges. In my case, I worked myself into a "corner" in the middle and couldn't fit holes where I wanted them.
At this point, I'm calling this done. I may revisit it later if it's still eating at me. I can, of course, cut out the offending section and go with the epoxied mesh.
Hope you find this little adventure useful.