Wow, a half inch blade? I've carried a small Swiss Army knife attached to my keychain for more than 10 years without a problem. The single knife blade is 1.5 inch long, and less than 1/4" wide (I just measured it.) On domestic flights, I always place my keys with the knife into the basket along side the metal detector before entering, and no one has ever said anything. On international flights, it goes into a carryon and through the X-ray in SFO and overseas with no problems.

Some years ago, a former colleague traveling with another colleague told me they almost missed a flight because the 2nd colleague's Swiss Army knife (larger than mine) had to be checked in when it was discovered at the security checkpoint.

The only extra checks I've encountered was that for a period last year, it seemed they would pick out my computer bag after it went through the X-ray to do the wipe (to analyze for explosives?) I then noticed after several trips with this happening that I had been carrying in it a bullet shaped laser pointer. I took that out, and have not had it happen to me since.