Zero Tolerance Ball Bearing

thingiverse

This design isn't intended for 3D Printing specifically, yet it's definitely possible. There are no spaces between parts, however you can use these ratios if you want to incorporate metal balls: The ball diameter is equal to sixty-seven percent of the race thickness (this refers to bearing height or thickness, not diameter). Alternatively, the race is 164.7% of the ball diameter. If you have a half-inch metal ball, the race thickness will be .824 (about thirteen sixteenths), but I recommend scaling it up slightly to create clearance gaps.