Test Nut Hole size device

thingiverse

I've been dealing with some issues when it comes to M3 nuts fitting into printed parts. The issue lies in the fact that nut holes are often too small due to thermal expansion, or a poorly planned slicing path. So, I designed this tool; it creates 5 six-sided holes. Each hole is progressively larger than the last. The first one has a 3mm radius, while the subsequent ones add an additional 5%, then 10%, and finally 20% respectively. By printing this design and inserting M3 nuts into each of the five holes, you can determine exactly what settings to use for a snug fit on your printer with Slic3r. After conducting some experiments, I found that adding 20% to the diameter (or 10% to the radius) results in nut-sized holes that require significant effort to push by hand. However, tapping them gently with a hammer or using pliers produces a tight, precise fit. Increasing the size increment to 10% of the diameter (or 5% of the radius) yields a hole into which I can easily push the M3 nut by hand; it remains snug enough for typical mechanical prints, however.