Drilling holes with very limited access

[samclem]

I thought about a Dremel, but I assumed it wouldn't be powerful enough to bore through 1/2-5/8" of fiberglass. Will it? I don't have one, but I am sure I could borrow one.

Yep, it will do it with no sweat. Probably either a high-speed steel wood rasp or a carbide rasp used for cutting ceramic tile would do the trick. Just don't try to use a tiny Harbor Freight rotary tool, etc.

1. I don't follow how a flex adapter would work for my situation?

Chuck the male end into your drill, put a hex-end drill bit in the female end of the flex drive. It lets you get the drill out of the way and align the drill bit very close to parallel with the green surface.

 

[Senator]

I would use a drill bit extension. I carry one in my tool box for these types of things. HD has them. Any bit with a hex end can be quick disconnected. Mine is ~12" long, plus the bit length.

 

[travelover]

I'm not sure if it would help, but I've had good luck with this 90 degree drill adapter from Horrible Fright and the price is right. It is usually on sale for around ten bucks

3/8 in. 90° Angle Drill Attachment

20% off coupon:

Digital Savings and Coupons from Harbor Freight

 

[Midpack]

One last thought worth mentioning - if aesthetics will allow, a number of smaller holes will drain the same amount of water as two large ones.

True, but one large hole is preferable in this case as there will be some debris (not just water) from time to time. Small holes will plug more often. But a good thought, thanks.

 

[ITTN]

Use Midpack's idea but double it. Start with two holes, with one placed opposite the other. Feed a round file through both holes, start enlarging the holes straight down with the file staying parallel to the green surface. With this approach you can't scratch the green surface under the blue arc.

 

[LoneAspen]

Is it the type of part that you could place, and secure, in a dress press and come down "from the top" (so to speak) with the long bit a dress press would provide?

It seems that would provide a lot of control in that the bit wouldn't waver, like a handheld tool might. If you could secure the part well enough, I bet you could lower the bit into it, and keep adjusting as needed, until you got as close to the green surface as possible without nicking it.

 

[target2019]

I was going to suggest you have a machine shop make up a jig that ensures success. But a jig like https://www.kregtool.com/store/c13/kreg-jigsreg/ might work.

 

[ERD50]

Here's an out-of-the-box approach:

Instead of attacking at an angle, use a Forster bit (will leave a small dimple/hole though) or an end-mill bit and drill straight down (perpendicular to the green base). This will cut through the channel and cut flush to the green base. A plus - the entire diameter will drain water, rather than just the edge of the 1/2" circle, so even a 1/4" hole will probably provide better drainage. You will probably need a portable drill press to guide it.

http://www.amazon.com/4Fl-SE-Carbide-End-Mill/dp/B000I6MPKO

edit - this might be what was suggested in #31

-ERD50