How To Avoid Failed Screw Holes In 3D Printed Parts

May 7, 2026 by Donald Papp 19 Comments

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.

There’s no reason to guess the right size of hole for a screw, just refer to some handy tables.

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.

A Trackball 3D Controller

April 27, 2026 by Jenny List 32 Comments

We use CAD packages in our 3D work, and it’s likely that many of us have become annoyed by the limitations of controlling the view of a 3D object using a 2D interface, our mouse. Joystick-like 3D controllers exist for this purpose, but [David Liu] found them inconvenient. He tried a trackball, but that didn’t improve matters. His response was to take the trackball and change the way it controlled the software, turning it from the equivalent of a ball rolling over a surface to a ball representing the object on the screen itself. He can turn and rotate the object intuitively just by moving the ball.

He started with a Kensington off-the-shelf trackball and adapted its electronics and handy twin optical sensors such that it worked in the required fashion. There was a lot of iterating and tuning to get the control feeling right, but he’s ended up with a peripheral that replaces both mouse and 3D joystick, and leaves the other hand free for those keyboard shortcuts.

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One Sailing Pulley To Rule Them All

March 6, 2026 by Bryan Cockfield 25 Comments

When thinking of humanity’s ability to harness wind energy, many people will conjure images of windmills from places like The Netherlands or Persia. But people have been using wind energy for far longer than that in the form of sailing ships. Using the wind for transportation goes back another four thousand years or so, but despite our vast experience navigating the seas with wind alone there is still some room for improvement. Many modern sailboats use a number of different pulleys to manage all of the rigging, but this new, open-source pulley can replace many of them.

The pulley, or “block” as they are sometimes called, is built with a polymer roller made out of a type of nylon, which has the benefit of being extremely durable and self-lubricating but is a bit expensive. Durability and lack of squeakiness is important in sailing applications, though. The body is made from CNC-machined aluminum and is composed of two parts, which pivot around the pulley’s axis to allow various ropes (or “lines”) to be inserted without freeing one end of the rope. In testing, this design outperformed some proprietary stainless steel pulleys of similar size.

Another perk of this design is that it can be set up to work in many different applications on a sailboat, whether that’s for hoisting a mainsail or pulling in a jib or any other task a pulley could be used for. It can also be stacked with others in many different configurations to build custom pulleys of almost any type, and can support up to 14 mm lines. For a sailor this could be extremely valuable, because as it stands each pulley on a ship tends to be used in only certain applications, and might also be proprietary from a specific company. This pulley is being released into the open-source world, allowing anyone to create them who wants one.

Thanks to [Keith] for the tip!

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STL Editing With FreeCAD

January 22, 2026 by Al Williams 28 Comments

[Kevin] admits that FreeCAD may not be the ideal tool for editing STL files. But it is possible, and he shares some practical advice in the video below. If you want to get the most out of your 3D printer, it pays to be able to create new parts, and FreeCAD is a fine option for that. However, sometimes you download an STL from the Internet, and it just isn’t quite what you need.

Unlike native CAD formats, STLs are meshes of triangles, so you get very large numbers of items, which can be unwieldy. The first trick is to get the object exactly centered. That’s easy if you know how, but not easy if you are just eyeballing it.

If you use the correct workbench, FreeCAD can analyze and fix mesh problems like non-manifold parts, flipped normals, and other issues. The example is a wheel with just over 6,000 faces, which is manageable. But complex objects may make FreeCAD slow. [Kevin] says you should be fine until the number of faces goes above 100,000. In that case, you can decimate the number of faces with, of course, a corresponding loss in resolution.

Once you are satisfied with the mesh, you can create a real FreeCAD shape from the mesh. The resulting object will be hollow, so the next step will be to convert the shape to a solid.

That still leaves many triangles when you really want flat surfaces to be, well, flat. The trick is to make a copy and use the “refine shape” option for the copy. Once you have a FreeCAD solid, you can do anything you can do in FreeCAD.

We’ve run our share of FreeCAD tips if you want more. There are other ways to tweak STLs, too.

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New Browser-based CAD System Is Best Friends With Triangle Meshes

December 4, 2025 by Donald Papp 41 Comments

Who’s interested in a brand new, from-scratch boundary representation (BREP) kernel? How about one that has no topological naming problem, a web-native parametric CAD front end to play with, and has CAD-type operations making friends with triangle meshes? If you’re intrigued, check out [mmiscool]’s BREP project.

Functioning (let alone feature-filled, or efficient) CAD systems are not a software project we see a whole lot of. Ones that represent models as genuine BREP structures but cleverly use mesh-based operations where it makes sense? Even less so.

In theory, CAD programs are simple: allow a user to define features, keep track of what they are and how they relate to one another, and perform operations on them as requested. In practice, it’s significant work. Chains of operations and dependencies easily become complex, volatile things and there is really no room for error.

Read [Arya Voronova]’s best practices for using FreeCAD to get a few hints as to what goes on behind the scenes in a modern CAD program, and the kinds of challenges the back end has to deal with, like the topological naming problem (TNP). A problem [mmiscool]’s implementation completely avoids, by the way.

There is a live demo at BREP.io which acts as a playground for the state of the project. You can get started by clicking the + button towards the top on the left panel to add features and operations to the history (like add a cube, then add chamfers or fillets, or extrude a face, and so on).

[mmiscool] points out that all computation is done client-side; even complex operations like fillets, lofts, and multi-body booleans execute directly in the browser with no need to be offloaded to a back end. BREP’s development is being documented on Hackaday.io and there is a video embedded below that gives an overview. Why don’t you give it a spin?

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How To Design 3D Printed Pins That Won’t Break

December 1, 2025 by Donald Papp 9 Comments

[Slant 3D] has a useful video explaining some thoughtful CAD techniques for designing 3D printed pins that don’t break and the concepts can be extended to similar features.

Sure, one can make pins stronger simply by upping infill density or increasing the number of perimeters, but those depend on having access to the slicer settings. If someone else is printing a part, that part’s designer has no actual control over these things. So how can one ensure sturdier pins without relying on specific print settings? [Slant 3D] covers two approaches.

The first approach includes making a pin thick, making it short (less leverage for stress), and adding a fillet to the sharp corner where the pin meets the rest of the part. Why? Because a rounded corner spreads stress out, compared to a sharp corner.

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MicroCAD Programs CAD

November 26, 2025 by Al Williams 40 Comments

We love and hate OpenSCAD. As programmers, we like describing objects we want to 3D print or otherwise model. As programmers, we hate all the strange things about OpenSCAD that make it not like a normal programming language. Maybe µCAD (or Microcad) is the answer. This new entry in the field lets you build things programmatically and is written in Rust.

In fact, the only way to get it right now is to build it from source using cargo. Assuming you already have Rust, that’s not hard. Simply enter: cargo install microcad. If you don’t already have Rust, well, then that’s a problem. However, we did try to build it, and despite having the native library libmanifold available, Rust couldn’t find it. You might have better luck.

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