[George C]

3 or 4 years ago my former team needed quite a few of them about dia 3". We had access to a lot of scrap pieces of 1" thick sheet UHMW. We rough sawed them round on a band saw, drilled a dia 1/2" hole, broached it to hex and then mounted the resulting blank on a piece of 1/2 hex shaft chucked up in a lathe. A hex shaft collar held it in place against the chuck jaws. As the UHMW is so soft, we were able to turn them to diameter in one (maybe two) pass. I ground a HSS cutter to profile - radius plus to match the dia of the polycord plus a taper back on each side to encourage the polycord to stay in its slot. Again, because UHMW is so soft, we were able to feed straight in to depth. If I recall, we used 1/4" polycord and went in about 1/2".

Some had to go on a round shaft so we left the hole round, broached a keyway and used a piece of keyed shaft for the mandrel. Some needed a set screw so we left a hub on the pulley and drilled and tapped for a grub screw.

It was cheaper than buying round bar and parting off pieces.