Drillholes for 120mm fan mounting are terrible- salvage how?

[Ephemeron]

In my SLK3700AMB I drilled holes for mounting fans with verax/direction sticks in between the original holes of the plastic mounting clip. Long story short, I messed up, drilling them way off center, one even being so close to one of the original holes that it almost unites with it to form one large one. It was a poor decision on my part to rush through these steps at the end of the night when I was already frustrated by other things.

The sticks themselves turned out to be too flimsy for my tastes so now I'd like to put in those grommets everyone is using from silcon acoustics and mcmaster. The drill size for the ones I ordered is apparently 3/16", much larger than the 7/64" that I found works for the verax sticks. So, I still might be able to save some face by enlarging the holes when I drill in the direction more like they should have been.

Still, this won't really work for the one hole I drilled that is just a hair from becoming one with the original hole.

Anyone have any suggestions about how I can salvage this mounting scheme? Is there a way to plug the holes up and drill again? While I'm here, any tips for drilling so that the bit doesn't slip away from you when you're pressing down, taking your hole way off center?

[Ralf Hutter]

While I'm here, any tips for drilling so that the bit doesn't slip away from you when you're pressing down, taking your hole way off center?

You need to use a sharp punch (a small nail would probably suffice, if that's all you have) along with a hammer and make a "locater mark" so the drill bit doesn't walk away from the correct location as you start to drill the hole.

Another good practice is to start with a pretty small drill first and drill a starter hole. This will serve to keep the finish-drill properly located as you're drilling.

My personal technique for drilling through most materials is to center-punch the hole first, then use a center-drill to drill a pilot hole, then finish up with a few progressively larger drills.

[Tibors]

Most of the time I put a piece of tape over the area I want to drill. You can draw on it and it prevents the slipping of the drill.

[Ephemeron]

Thanks for the tips! Live and learn, I guess.

In any case, I've got the bondo and the jbweld out, so I think I'll be alright. Not that I've used them before; I'll just take my time to get it right go around.

When I'm ready to drill again I think I'll both lay down a piece of tape then use a nail to punch a center mark. Perhaps even start with a small bit then go larger.

[rtsai]

First time modding, and you're already breaking out the power tools?

Brave. It took me forever to work up the courage just to 7V my molexes and snip out my fan grills.

[Straker]

instantly thought "jb weld" when i read your initial post, but you already thought of that, should work fine... but unless the original hole is huge, i don't think it'd even be a problem if they became a sort of lopsided slot as long as there's no sharp point between the two. Remember some cases/enclosures etc simply use slots instead of holes (drive cages being an even more obvious example) to accomodate different fans, so I'd doubt any grommets/soft mounts would be seriously compromised if you couldn't quite keep the two holes separate.

[Gooserider]

I wouldn't try to 'walk' the hole over with a drill, that is asking for problems. Instead I would use a 'rat tail' or round file to enlarge the hole only on the direction you need to moove it. I have used this technique to recover many times with excellent results.

If you have trouble finding a round file that is small enough in ID, look for needle or jewlers files, they usually come in sets and are fairly low cost. Yuo could also try one of the files used for sharpening a chainsaw.

I would agree with the suggestion of using a center punch to mark your hole location. Tape is also good when you need to mark things up, but IMHO you should still use a centerpunch with tape.

I don't think you really need to worry about filling the old holes w/ JB or bondo, but if you do, I'd wait until after you had fixed the holes to work properly and then do the filling as a last cosmetic step. Don't try to fill the holes and redrill unless you will be going into completely new metal. Any sort of fill will have a different hardness than the original metal, and drilling into a hole with different hardnesses is difficult and tricky at best, you are likely to follow the path of the old hole and / or break drill bits, the file will be easier.

Gooserider

[the_e_dean]

oops

[matt_garman]

I can't help too much with your current situation, but in the future, you might want to try Bluefront's technique for soft-mounting fans as discussed here. Basically, you use cable ties and rubber hosing to mount and isolate the fan from the case. The cables allow you to get away with using case holes that don't match up with your fan's mount holes exactly.