Drilling larger holes in tight quarters...

[Michael Burbidge]

Unfortunately I did not give enough thought to where I want my antennas before putting together the center fuselage section. I would like to install my transponder and COM antenna under the baggage floor on opposite sides.

To do this I need to drill wire run holes in two of the baggage ribs. I think the holes will need to be 1/2 - 5/8 inch in diameter. I have a 90 degree angle drill but can only get bits up to a 1/4 inch for that drill.

My unibit and regular air drill will not fit between the ribs.

Are the any suggestions as to how I might drill wire run holes in already installed baggage ribs? Do they make larger than 1/4 inch bits for the 90 degree angle drills?

Thanks,
Michael-

[Andrew M]

I have a "blair cutter". It is a small hole saw used for cutting out spot welds. The cutting bits are different size and use a 5/16 dia. something to thread to the arbor. The arbor has a 1/8" hole for the pilot shank. To make the tooling (special arbor);
1 select a bolt with the same thread as the cutter
2 clamp a piece of (wet) wood to the drill press table and drill for the bolt size (5/16")
3 put the bolt in the hole and drill 1/8" for the pilot. go all the way through if it is drilling true.
4 drill part way through number 3 (I think for 1/4-28 tap) and tap part way. The head needs to come off the bolt sometime as well
5 super glue an 1/8" bit shank into the pilot hole
6 screw a short piece of 1/4 28 all thread into the other end
Drill a pilot where you want your hole, cause now you have a 90 degree collet hole saw adapter.
Hope you follow, P.M. me if you would like to talk.

Andrew
AP IA
-9 preview

[kevinh]

Originally Posted by Michael Burbidge

Are the any suggestions as to how I might drill wire run holes in already installed baggage ribs? Do they make larger than 1/4 inch bits for the 90 degree angle drills?

I made the same mistake. The countersink bits will screw into the the angle drill - so I 'countersunk' my way through the one hole I needed.

[Phil]

Another possible solution is to drill the 1/4" hole and then use a knockout punch to reach the final size. That's what I had to do in a few areas where I was passing conduit through some areas too tight for a drill and unibit.

Phil

[John Tierney]

I had similar problem when I forgot to drill some holes in wing ribs for conduit. I used someone else's idea and filed the shaft of a Unibit into the a six sided shape. After wrapping the shaft wih masking tape it fit nicely in a 9 mm socket, for which I had adaptors to fit in a drill. However, I did not have to turn 90-degrees. Perhaps a pneumatic ratchet driver would work if it turns fast enough.

[Camillo]

I did the same as Kevin. I used a countersink bit.
The procedure is already explained by Vern's Little in his site.

[bruceh]

I forgot to enlarge the tooling holes in the seat ribs for the wiring runs out to the wings. I bought a cheap 3/4" unibit from Harbor Freight. It has a hex drive that was just a bit too large for my Avery angle drill adapter. I had to grind down the hex drive and round it out enough to be able to get it into the 1/4" chuck on the angle adapter. From there it was easy to get the unibit/angle adapter in between the seat ribs and enlarge those tooling holes.

[az_gila]

Originally Posted by bruceh

I forgot to enlarge the tooling holes in the seat ribs for the wiring runs out to the wings. I bought a cheap 3/4" unibit from Harbor Freight. It has a hex drive that was just a bit too large for my Avery angle drill adapter. I had to grind down the hex drive and round it out enough to be able to get it into the 1/4" chuck on the angle adapter. From there it was easy to get the unibit/angle adapter in between the seat ribs and enlarge those tooling holes.

...the HF unibit shaft can be made to fit in a round 1/4 holder as mentioned above.

Then you can use a cheap HF angle die grinder as a drill if you don't have an angle drill adapter that has a chuck.

UPDATE

After checking in my workshop, a real Unibit already has a 1/4 round shaft, so it will clamp in your angle die grinder with no modification.

I just used this combo today....



Try and borrow a real Unibit...

[BillSchlatterer]

While there picking up a couple of uni-bits, they have a nice right angle adapter that goes in a regular drill. It will take up to the one inch uni bit with no sweat. Fits in the area you mentioned fine. Less than $20 if I remember correctly.

Bill S
7a on the verge!