Insert a 806 radial bearings from the Mc-Master Carr online store.
Start a new sketch and draw a center diameter circle from the center of the 806 radial bearing, the circle's diameter should match the outer diameter of the bearing.
Hide the bearing from screen, and draw another center diameter circle concentric with the previous one. The new circle's diameter is 27 mm.
Draw a construction line that start from the center of the circles, its length is 29 mm and it should be parallel to the Y-axis.
Draw 2 concentric circles with the same diameters of the previous ones, 22 and 27 mm, where the center is the upper point of the construction line from step 4.
Copy the construction line to right, at 13.5 mm distance.
Copy the construction line to left, at -13.5 mm distance.
Trim the upper half of the lower 27 mm circle and the the lower half of the upper 27 mm circle.
Now we will create a circular patern, first, we will select the indicated blue lines in screenshot below.
Now, we will select the center point, which is the center of the first drawn circle around the 806 bearing, and put a quantity of 3.
Trim all the extra line inside the primeter of the fidget spinner as shown below.
Stop the sketch, select the fidget spinner's design and extrude it to 7 mm.
The fidget spinner's design is now done and ready for printing. Save the extruded body as an STL file.
Import the STL file into Makerbot Print 3D Printing Software to slice the design. Set the infill to 20%, and layer height to 0.2 mm. No supports are need considering that the design is entirely flat and no hanging parts. The estimated weight of the design is about 9 grams and estimated time to finish the print is about 2 hrs.
After the print is done, seperate it from the printer's plate carefully using an object with a thin sharp edge.
Remove the raft from the bottom and now the fidget spinner is ready for some action!