A cartridge bearing should have an interference fit with its hub bore. Some hubs hold their bearings firmly and others are too loose. At first glance a slip fit seems simpler for the DIY mechanic but a slip fit can allow slight play in the wheel. Play is no good because it’s your cue adjustment is lost or bearings are worn. Unnecessary play can damage hubs.
These hubs are a good example — out of the box I found the bearings slightly loose. In cases like this I re-install bearings with a thin layer of Loctite 641 applied to the outer races. Loctite makes a variety of industrial bearing retainer compounds but I use 641 because it’s a low viscosity formula that allows for thin applications. It’s the lowest strength sold, which means bearings can be pulled easily in the future.
