Sintered metal bushings soaked with oil.  Chrysler invented them around 1930.  Trademarked name is &quot;oilite&quot;.  A very popular product for many decades, probably some in your car or house today.  It really blows some peoples minds when what looks like a block of solid bronze soaks up to maybe a fifth its volume of oil.  For something thats 20% hollow its also remarkably strong.<p>Its an example of a piece of technology that depends on numerous contemporary things.  You need razor sharp cutting tools to keep the pores open, so it has to be a &quot;post-carbide&quot; era tool.  You need a vacuum pump to fill the pores with oil.  You need modern non-drying low acidity mineral oils because something like veg oil or whale oil would break down both the bearing and the shaft in a couple years.  The powder is heated precisely and under some pressure, a lot more precise than a blacksmiths shop.<p>Speaking of pressure, reproducible and reliable sintering seems to always require some amount of pressure, which is a problem for 3-d printing, either you&#x27;re using somewhat exotic process, or the product needed pressure so it is going to be weak.