Screws are useful fasteners for 3D prints, but the effectiveness of a screw (not to mention the ease or hassle of insertion) depends on the hole itself. This comprehensive guide on how to design screw holes in 3D printed parts takes guesswork out by providing reference tables as well as useful general tips.
The guide provides handy tables saying exactly how big to design a hole depending on screw type, material (PLA, PETG, or high-flow PETG) and whether the hole is printed in a vertical or horizontal orientation. This takes the guesswork out of screw hole design.
The reason for different numbers is because multiple (but predictable) variables affect a 3D-printed hole’s final dimensions. Shrinkage, filament properties, and printing orientation can all measurably affect small features like screw holes; accounting for these is the difference between a good fit, and cracking or stripping.
In addition to the tables, there are loads of other useful tips. Designing lead-ins makes screws easier to insert and engage, and while increasing walls is an easy way to add strength it’s also possible to use 3D-printed microfeatures which are more resistant to distortion and don’t depend on slicer settings. There’s even suggested torque amounts for different screw and material types.
Sure, the most reliable way to get a hole of a known size is to drill it out yourself. But that’s an extra step, and drill bits aren’t always at hand in the desired sizes. The guide shows that it is entirely possible to print an ideal screw hole by taking a few variables into account.
If your design calls for screws, be sure to check it out and see if there’s anything you can use in your own designs.
Well, it’s reverse from what I would think. Vertical HOLE means that axis of the hole is vertical (axis right angle to bed), right? Here they mean that when SURFACE is right angle, it’s a hole in vertical surface, which makes it a vertical hole :/
Aahh… the first seeds of world wide confusion has been planted.
We’re screwed…
I love the sense of humor on the comments section! Makes my day!!
There’s also the way that doesn’t overcomplicate the design and give a strong result even with screws designed for metal:
– Draw the holes like you would for metal
– Print with enough perimeters to allow strong tightening
– Drill the size you would for metal, because holes are always smaller than expected and not smooth
– Hot mount the screws: heat up the screw with a lighter and screw while hot (easy with BTR screws).
– Chamfer / clean the hole entrance with a large drill bit
I found the result stronger than using cold mounted metal inserts.
If you print with more perimeters and then drill out the hole to size, you can as well just tap it properly then.
That said, for small-ish metal screws (M2.5 to M4 or so) that don’t see a lot of load (e.g. for holding on a lid or something of that matter), you can just screw them in and let them form their thread on their own. They will get rather warm due to all the friction, so you need to take care not to overtighten them lest they strip their thread immediately.