OT: drilling problem

[markus shaffer]

i was hoping some one here might have a solution to a drilling problem i have. i need to drill a fairly large diameter hole through two walls of a music studio. from the inside of one wall to the outside of the other the distance is roughly 20 inches. what i need to do is put about a 3 to 4 inch diameter hole through both walls. i know i can get a long enough standard bit to drill all the way through both walls to line up the holes. the idea is to run a length of pvc through the walls so that cables can be run into the studio from the outside. i thought of using a standard hole saw or even a forstner bit, but i havn't seen any with a shank long enough to reach all the way through one wall. each wall is 2x4 construction sheeted with a layer of 5/8" sheetrock, 5/8" osb on one side and 1/2" soundstop and 1/2" sheetrock on the other, so i'll need something with a reach of about 6 inches. also, with the two layers of osb, i'll need something that's somewhat strong. any ideas anyone might have would be greatly appreciated. thanks..

-markus

[Bruce Page]

Marcus, Can you drill through both walls with a long 1/4" drill for location and follow with the hole saw from each side?

If I am understanding your question correctly, it seems like that should work.

[Tony Laros]

I have hole saws up to 4½", but they won't reach 6". I would suggest lining up the 4 holes with a small diameter bit, and making the 3 or 4" hole in the 2 outside walls, and using a recip saw for the internal partitions.

[Phil Phelps]

...but they make a hole saw on a cylinder in various lengths. My electrician has one of 24" in length. They can be rented.