Summary

This Batarang Fidget Spinner has beveled edges and embedded nuts for a smooth surface finish.
Print two of these parts, install the 5/16 inch nuts and then glue the two halves together.
Uses a standard 5/16 inch hex nuts along with a single standard 608 bearing

Print Settings

Printer Brand:

LulzBot

                                            <p class="detail-setting printer"><strong>Printer: </strong>                     <div><p>Mini</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>0.3 mm</p></div></p>                                                                                <p class="detail-setting infill"><strong>Infill: </strong>                     <div><p>20%</p></div></p>

Post-Printing

Print two of these (each half) and then embed nuts for counter weights before gluing the two halves together.

Printing without a bottom layer and ~20% infill gives lots of surface area for the glue to adhere. Use polyurethan adhesive (Gorilla Glue brand) or cryanoacrylate gel adhesive (Super Glue brand Gel) for best results

Use four 5/16 inch standard hex nuts commonly found in hardware stores in the US
http://www.engineershandbook.com/Tables/nuts.htm

How I Designed This

I designed this using 3Dorchard.com
You can see the iteration design tree and make your own branch at https://www.3dorchard.com/app/single/59eebbb14464900b77bbbc90/5a179dd37f964a0d2262e691