the hole for a 1/2 coupler will be close to 1". I got mine from buyfittingsonline.com and they were great to work with. The step bit I got from harbor freight was worthless as many have found out. I ended up using a 1" hole saw and cleaning up the opening with a die grinder. Make sure you have your fittings on hand before you drill!! I have a set of digital calipers I measured the fittings prior to drilling, with chinese product you can never be too careful. Good luck!
Primary 1: empty
Primary 2: empty
Primary 3: still at LHBS waiting for me to purchase
Secondary 1: empty
Secondary 2: empty
Secondary 3: empty
Kegged: New Belgium Ranger IPA Clone attempt #1
Bottled Southern Tier Pumking Clone
Planned: EdWort's haus pale ale
CBC Bodhi IPA
I may be naive but I make up for that with inexperience!!