Summary

I wanted to make a fidget spinner with a minimalistic design. This is what I came up with. This will fit a standard 8mm x 22mm x 7mm bearing, as found in inline skates.

This was designed using OpenSCAD.

Versions:
v2.4: Much improved reliability with a sandwich design (recommended for printing)
v1.1: Improved design with more reliable structure
v1.0: Initial upload.

Print Settings

Printer Brand:

Printrbot

                                            <p class="detail-setting printer"><strong>Printer: </strong>                     <div><p>Printrbot Simple Metal</p></div></p>                                                                                <p class="detail-setting rafts"><strong>Rafts: </strong>                     <div><p>No</p></div></p>                                                                                <p class="detail-setting supports"><strong>Supports: </strong>                     <div><p>No</p></div></p>                                                                                <p class="detail-setting resolution"><strong>Resolution: </strong>                     <div><p>0.2</p></div></p>                                                                                <p class="detail-setting infill"><strong>Infill: </strong>                     <div><p>100</p></div></p>                                                        <br>                        <p class="detail-setting notes"><strong>Notes: </strong>                    </p><div><p>With the old models the PLA was too brittle for the press-fit center hub, resulting in cracks. The new sandwich style model prints well in PLA as well as ABS now. </p></div>

Post-Printing

After printing you can clean up the print if you want, but mostly it's ready to add the bearings.
You need three bearings this super simple spinner. Place the spinner on a hard flat surface and set a bearing level on the center hole. It should insert pretty easily, but be gentle and be sure to press it all the way in.
The two side bearings are slip onto the mounting posts easily. Before you add the top of the "sandwich, it is best to clean up the mounting holes and pegs a bit. Hold the top piece (with the pegs) at an offset angle so you can insert the pegs one at a time. Rotate each peg in its matching hole and put it in and out a few times so that it fits without being too tight.
Now you can add the top piece to complete the "sandwich".
Install the two beveled caps onto the center bearing. They should extend about 1mm past the spinner body, so you can set the spinner on a table and spin it.

How I Designed This

Using Math in OpenSCAD

            <div><p>I included the OpenSCAD file I used to generate the STL file on this thing. </p><p>Many iterations; trial and error.</p></div>

Super Simple Fidget Spinner