I gotta say, you got some mad drawing skills. lol in ink no less. I've seen plastic washers like that fairly common, but not in that size shaft. They are hollow throughout (not a solid washer base)....both metal and plastic, but the ones we have used were for 5/8" sized bolts, and im not sure of the "shaft" length on them. I'll see if I have any more in the garage.
You are correct, any thread will work if it will screw onto the cylinder. Threads are the only way that I can think of to make the washer be able to stay a set distance from the other washer. (sorry if that doesn't make sense, i'm definitely not a machinist :d ) It can be as large as you need it, but at least 3/32"... is that possible?
