First, I really hope you like the design and find it useful. If you feel like tipping, rather than hitting the "Tip Designer" button, PLEASE donate to UKRAINE (or any other people in need). These people will need any help they can get (and they will need it a lot more than I do)! THANKS!!

UPDATE 07May21: Hi All, I have just added a second set of smaller bearings down to 685 (which is just 11 mm outer diameter). https://www.thingiverse.com/thing:4851975

UPDATE 30Apr21: Hi All, I have just uploaded a set of fidget spinners using the 608 bearings. Perfect to try out that printed bearing of yours. Enjoy!
https://www.thingiverse.com/thing:4843825

Spherical Roller Bearings

A set of spherical all purpose roller bearings in five common sizes: 608, 609, 6000, 6002, and 6004. So strictly speaking these are not ball bearings (which are extremely difficult to print) but they serve exactly the same purpose and can run just as smooth. They are (moderately) easy to print and with a little grease work just like their steel counterparts. They are all print-in-place, which means that you only need to print a single piece and that there is no assembly involved.

Use for a wide range of applications (filament guides, spool holders, fidget spinners, RC cars, robots, perpetua mobilia...) where you don't need the durability of steel bearings (I fear they won't be any good on your car, skateboard, bicycle...). In my experience they run a lot smoother than (but are not as sturdy as) their steel counterparts.

They come in five different sizes, and two flavors - narrow (named tolMin) and wide (tolMax) clearance (please see below for clearance. Measures are inner x outer diameter x width):

• 608: 8 x 22 x 7 mm (0.31 x 0.87 x 0.28") - which is the counterpart to this one
• 609: 9 x 24 x 7 mm (0.35 x 0.94 x 0.28") - and its steel counterpart
• 6000: 10 x 26 x 8 mm (0.39 x 1.02 x 0.31") - its steel counterpart
• 6002: 15 x 32 x 9 mm (0.59 x 1.26 x 0.35") - its steel counterpart
• 6004: 20 x 42 x 12 mm (0.79 x 1.65 x 0.47") - its steel counterpart

UPDATE 27Apr21: I have added a tolUltra version for 608, for those who find the tolMin version too easy to print. ;-)

Filament.

• As usual I print mine using a cheap, strong, and easy to print Carbon Fiber PLA (but any strong filament will do - I have only tried PLA)
• and in Silk Silver.

Printing. For many of my designs this section would start with "print with any infill and resolution, in your favorite filament and color". However, even well designed bearings are a little tricky to print and I fear I can't actually give you a one-fits-all recipe for printing. You'll have to try out yourself (it is all small prints, so you won't lose a lot of filament). Once you have your optimal settings established they are really easy to print. So here a few tips:

• I have included a low (named tolMin) and a high (tolMax) clearance version of each bearing for you to try. My personal experience is that I can use the high clearance version right off the printer bed (after a little squeezing and rolling) but they tend to be a little wobbly, whereas the narrow ones usually need some individual attention to losen each part (do this with the tip of a knife or small screwdriver). I would definitely start with the high clearance variety and with one of the larger bearings.
• Experiment with different filaments. Carbon fiber PLA (see above - the CF PLA I use is actually more of a carbon particle filament) - works perfectly for me, also because it sticks real well to the printer bed and is very easy to print.
• Print slow. I mean real slow. Slow like 10 mm/s for the first layer, 20-25 for the rest. Make sure that all those little details stick to your printer bed (I use a higher bed temperature for the first layer).
• Make sure that you are not printing elephant's feet.
• I use 0.1 - 0.12 mm resolution (but 0.2 with adaptive layers also works for me, at least for the slightly bigger bearings) and 30% (lines) infill.
• Set your Z-seam alignment to random.
• Reduce flow (I use 90% flow for all bearings).
• Set "Fill Gaps Between Walls" (Cura) to "Nowhere" (thanks to the folks who pointed this out)

Finally, you can (optional but recommended) add a drop of e.g. silicone or PTFE lubricant. Makes them spin like crazy... ;-)

HOPE YOU LIKE THEM, AND IF YOU LIKE THEM, PLEASE LIKE THEM. THANKS!

Enjoy and happy printing!

UPDATE 19Apr21: I have updated all .STLs to V2.0, which should make printing even easier (V2.0 adds 0.05 mm clearance to the cage only).