Dowel Pins: Elegant Connection without Nuts (for M3 and M4 Screws)

Usage

The dowel pin is designed to fit precisely into the BitBeam block hole (ø 4.8 mm). When screwing in an M3 (4-40) or M4 (8-32) screw, the inner body of the dowel expands and is firmly anchored in the wall of the block—similar to a classic wall plug, as shown in the image below.

Detailed view of the dowel pins with M3 and M4 screws screwed in.

Recommended printing is with PET-G, or PC (Polycarbonate) for greater stiffness.

The dowel pin fits into the block hole very snugly, but even a skilled child can manage it. You can, of course, help yourself with a 3D-printed tool, or a small hammer.

When screwing, it is necessary to press the screw a little harder, as the initial expansion of the dowel pin is slightly more challenging. Alternatively, the dowel pin can be pre-expanded in the block with a screwdriver to better catch the first thread.

Some screws have a tip, or at least a small rounding at the beginning of the thread, which will "catch" better, similar to wood screws. However, the threads of wood screws look significantly different, and there are many types. It is therefore not within our capabilities to test or mention suitable types of wood screws. However, feel free to share your experiences in the forum.

Choose the length of the screws used so that the thread engages at least 3/4 of the length of the dowel pin, meaning 6 mm should be screwed into the hole with the dowel pin. This will cover the entire thickness of the dowel pin. 5 mm may be sufficient for some situations. However, keep in mind that the dowel pin only begins in the hole after two millimeters.

Advantages of Using Dowel Pins over Nuts

Assembled structure using dowel pins and M4x16 screws

• Speed and Ease of Assembly: Screwing is now significantly faster! You don't have to worry about whether the nut will fit into a confined space or whether you can hold it while screwing. This facilitates the assembly of structures without the need to leave free access to the nut opposite the screw.
• Space Saving and Clean Design: The structure is more compact and aesthetic—you no longer see the nut on the other side of the joint. The space behind the dowel pin can thus be used to place another building block. The structure is also lighter because the dowel pins do not weigh as much as the nuts.
• Ideal for Robotics: They ensure a sufficiently strong connection for robotic building systems and autonomous robots. Thanks to the plastic dowel pins, the screws remain in place even during vibrations that cause the gradual loosening of nuts.
• Connection Alternative: BitBeam expands the use of screws as a fastening material. Thanks to the use of M3 / 4-40 screws, it can also be more easily combined with other building systems working with smaller screws. You thus gain greater flexibility for your project, whether you are building complex robots or simple models, and we are creating a strong alternative to bitbeam4.
• For STEM Projects and Education: They simplify working with the construction system in a school environment, where speed and the frustration of dealing with nuts are key. Furthermore, unlike nuts, you can 3D print the dowel pins.

Conclusion

BitBeam Dowel Pins represent a significant step forward in the simplicity and elegance of screwing, especially for projects that are exposed to vibrations. They simplify construction and allow you to focus on creativity, not on manipulating small nuts.

Try the new dowel pins and take your projects to a new level.

References:

• stl dowel pins for M4 or 8/32 screws
• stl dowel pins for M3 or 4/40 screws

Diagram of the dowel pin for M4 or 8/32 screws with dimensions in mm.