Any of those would be powder metallurgy (oilite, or super
oilite). If they were just simply made from a solid bronze
bushing where would they get any lubrication from???
Oilite can be bronze or iron based, either way they are vacuum
impregnated with enough lubricant for the life of the bearing.
I think the "relief" cuts that Novak is talking about just
means that there isn't as much bearing surface in those,
therefore that would wear out sooner than one with 100%
bearing surface.
There is no magic to making a pilot bearing. You could get a
chunk of solid material from McMaster Carr:
http://www.mcmaster.com/#sae-841-bronze-rods/=z5b23g and with a bench lathe and good sharp carbide bits turn out
your own bearing. But why bother when you can buy them
already made for about $3 from Classic parts.
http://www.classicparts.com/Trk1Flip/index.html#95/zdg
