I screwed up! I picked up an older Schwinn aluminum frame and the INSIDE diameter of the frame head tube is 1-3/16'' as measured with caliper. When I originally measured it with rule I had come up with 1-1/8'' and ordered a threadless headset accordingly; which of course, doesn't fit. The frame originally had a pressed in/threadless headset but I'm in a quandary as to what size headset is required. I bought a FSA Orbit MX 1 1/8'', which has the same internal diameter as my head tube. Any suggestions would be much appreciated!

Not sure what you mean by inside diameter of the headset. How about the fork steerer tube diameter and crown race seat diameter?

Sorry, I mis-spoke, meant to say the internal diameter of the headtube is 1 3/16''; in reflection, I suspect my frame accepts a 1'' steerer/headset. Great! I have an 1 1/8'' carbon fork on the way....

Hang on to the headset and fork for when you get to N+1 stage.

Heck of a learning experience so far...started out with my 1990 Raleigh 12spd Reynolds chrmolly frame and decided to upgrade. Picked up Schimano 105 triple crank & BB, 105 rear derailleur, sram 9 sp cassette, sram rival brakes, all new jagwire cables. BUT then I saw the Schwinn frame on ebay, decided to go the aluminum route. Neglected to make note of the 1" head tube --- Now have all the above, as well as Ritchey handlebar, with shimano bar end shifters, TWO different 1 1/8" headsets, and the carbon fork (1-1/8") due in tomorrow. Really don't want to stay with the Raleigh frame, so I guess I'll be in the market for ANOTHER fork & headset....hopefully will have this mess all put together before the snow flies.

I'm a 'newbie' so I'll bite, what is "N+1" referring to?

N is your current number of bikes. +1 is the NEXT one.

Vintage Specialized MTB Rockshock/hard tail.
1976 Schwinn Hurricane, frame being re-painted, powdercoated/clearcoat as we speak.
1990 Raleigh cromoly, currently in pieces.
Enough NOS, new and used parts/pieces to make up some semblance of a decent roadbike lol