Originally Posted by
cyccommute
As my Pappy used to say: "Hogwarsh!" The tubing used for a threaded or threadless fork has the same diameter and "finish". You seem to be implying that threadless steer tubes are an inferior product which is not what I have observed in a couple of decades of bicycle wrenching. .
I don't know what your Pappy used to wash hogs, but I doubt he said this as loosely as you're willing to. Fact is fork steerers come with various thickness walls.
This is just another example where the simple act of measuring would trump all the expertise or opinions here. Steerers intended for threading usually have a 1/16" wall and take a quill stem 1/8" smaller in diameter than the stem - ie. 1" fork = 7/8" stem, 11-1/8" fork = 1" (actual) stem.
There are exceptions to this, such as BMX forks which often have thicker walls and take a smaller .833" stem.
So that answers the first question ---
1" Steerer ID's are not all the same.
This also works in the opposite direction, with some makers of steel threadless forks using thinner tubes, resulting in a larger than standard ID. Not only isn't there enough wall to thread, there aren't any stems to match the larger ID.
So before anyone even consider cutting and threading a fork, they must first check whether a quill stem will fit. That will automatically answer whether it can be made into a threaded fork.