Summary

This design is meant for Arduino Uno Rev3. It requires M3 screws (26.2mm including head).
Only three screws are used because there is no space left to accommodate the countersink between the pin slot and the screw hole.

Print Settings

Printer:

Geeetech i3 Pro B

                                            <p class="detail-setting rafts"><strong>Rafts: </strong>                     <div><p>No</p></div></p>                                                                                <p class="detail-setting supports"><strong>Supports: </strong>                     <div><p>Yes</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>20</p></div></p>                                                        <br>                        <p class="detail-setting notes"><strong>Notes: </strong>                    </p><div><p>I printed the model using a 0.3 nozzle:<br>First Layer Height: 0.3<br>Layer Height: 0.2<br>Layer Width: 0.51<br>Perimeters: 3<br>Slicer: Slic3r 1.2.9</p><p>Concerning supports, it is arduous to tear the supports off the screw/nuts holes. It helps setting interface layer to 1. I have tried rectilinear and pillars support without noticing much difference. Suggestions are welcome.</p></div>

Arduino Uno Rev3 case