I'm using brass. I found a couple brass fittings that will fit on a
15mm or 5/8" shaft whichever I can find. I'll see what our local Metals Supermarket has available. We are under lockdown up here and getting ANYTHING is a long drawn out affair. The Myford Super 7 can help me make what I need out of what I have or can scrounge. I have HMWPe that I could make the bushings out of too but I think it would be more likely to deform under the load when opened.
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The nominal ID of 1/2" pipe is 0.622".
I made the pivots for the hydraulic bucket loader for my garden tractor from
3/8" brass pipe nipples (ID 0.493") and 0.500" O1 drill rod. When I disassembled it several years later one pin was measurably but not visibly bent from hitting a stone step under the snow but the well-greased brass bearings were like new.
Cut off ends of brass nipples are valuable as mandrels with pipe threads that run true to the chucked OD.
TIG welding retaining plates onto one end of the drill rod created a brittle zone beside the weld that I had to anneal. Replacements for pins that broke were cross-drilled for retainers instead. The problem is that the pivot pin has to be rigidly attached to the thinner outer members of the fork joint so only the larger steel/brass surface rotates.
Parts diagrams for front end loaders show how manufacturers have designed the pivot components. Bucket loaders are cut and assembled from stock shapes of plate and rectangular tubing in ways applicable to hobby construction. The hardest problem I faced was keeping widely separated bearing bores sufficiently parallel.
I'd consider oilite sleeves for the bicycle carrier, because plastic can be difficult to machine to size. The design bearing pressure in my loader exceeded oilite's rating.
I stopped using the loader and bought snow blowers because I had repaved the driveway. The bucket chewed up soil and the edges of asphalt when snow fell on mushy thawed ground that didn't support the skid plates.