Summary

For when you need a bunch of 7 mm (M4) spanners/wrenches for a class that just needs one nut tightened slightly beyond finger tight …

Print Settings

Printer:

Reach 3D

                                            <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 mm</p></div></p>                                                                                <p class="detail-setting infill"><strong>Infill: </strong>                     <div><p>66%</p></div></p>                                                        <br>                        <p class="detail-setting notes"><strong>Notes: </strong>                    </p><div><p>As designed, there's only 7.4 mm between flats, so please try a test print and adjust the value of the variable <em>slop</em> in the OpenSCAD code accordingly.</p><p>Print with a fairly high shell and top and bottom layer count for a stronger tool.</p><p>Uses Google <a rel="nofollow" href="https://fonts.google.com/specimen/Roboto">Roboto</a> Thin for engraving. Feel free to change the value of the variable <em>msg</em> in the code to get a different inscription. If you have a fast machine, swap the comment from <code>fancy_inscription()</code> to <code>inscription()</code> in the <code>spanner()</code> module for nicer rounded text at a truly colossal computational cost.</p></div>

Post-Printing

Check that these will actually fit an M4 nut before handing these out in a class.

The OpenSCAD source makes two units, and you can easily fit multiple sets on a print bed.

How I Designed This

While this design isn't really intended as a fully parametric part, all of its dimensions are controlled by three(ish) variables in OpenSCAD:

nut_thick — thickness of the nut in mm. Default: 3.2
nut_nom_flats — nominal size of the nut in mm. Default: 7 mm
slop — print tolerance in mm. Default: 0.2 mm, giving a design size of 7.4 mm
(optional) msg — the text printed along the handle. Doesn't affect the size of the part, and can be left blank. Practical limit is 6-7 characters, unless you want to fiddle with the text sizing in the inscription() module.

A link to an M-series nut sizing chart (Dimensions of Metric Hex Nuts from Fairbury Fasteners) is given in the source code.

Better-Than-Finger-Tight 7 mm (M4) Spanner