To follow up on what Thomas said about over heating certain steels, it helps immensely to get your forge inside so that you can see the colors of the material without "light contamination" from sunlight. Trying to gauge heat temps in bright sunlight is a sure way to over heat the piece.
I used a pair of 1" wide bearings scrounged from an electric motor re-build shop. I ganged two of them side by side to give me a 2" wide idler. See pics at BluePrint 354.
Oops, we have to go back to CALF because we can only change one letter at a time (CLEF changes two letters)... so from CALF, we can get HALF, HALF, HALF.