RackStuds for M6 10"/6" racks

Update 1.3: Tightened tolerances on stud shaft and hex head close to v1.1-1.0. Threads almost like 1.2. 



RackStuds - a strong™ threaded fastener.

This two-part design aims to make 3D printed mini-racks a lot more fun and accessible by eliminating a trip or two to the hardware store. The studs are 100% compatible with the rack rails from McBig and Natalie T, and it seems a lot of other designs are borrowing dimensions from these foundational works, so compatibility should reach further and further as time goes on. Other printed options do exist, but none have so far provided the strength and ease of use I was seeking.

The RackStuds probably do exactly what you think they'll do. Further reading is optional.
 

Studs, you say? 

Now, hear me out… I know these look like unproportionate nuts and bolts, but they are designed to go the other way around. 

The stud (bolt) goes in first, from the back of the rail, and seats tightly within the hex slot. Two benefits are found with this approach. Firstly, they don't fall out unlike regular M6 nuts. Secondly, they will hold a blanking plate, shelf or rackmount temporarily during installation. 

That makes things a lot easier. The nut goes on last, and can be tightened by hand or with the help of a 10mm socket.

Why the split?

The stud is split down the middle and folded out on the printbed for two reasons. Doing this ensures that there are no overhangs whatsoever, so the threads are formed as nicely as possible. Also, this means that the load is in plane with the layer lines, so the studs become surprisingly strong despite the pesky size. 

The split itself is unproblematic when the stud is installed because both the rails and the nut compress the two halves firmly.

The nut, on the other hand, is printed vertically because there is a lot of force trying to split it apart. This does compromise tensile strength in the Z-direction, so to compensate the first few threads are quite shallow, allowing the pulling forces to spread further into the nut.

 

That doesn't look anything like M6 x 1mm…

Nothing here follows ISO standards, and for good reason! Standard M6 threads are terribly weak when printed on consumer hardware. This is a custom thread profile with a 2.6mm pitch. As such, nothing here will interface with M6 threads. However, they go in the same holes that M6 fasteners go into, so I hereby declare them M6 equivalent.
 

Problem? No problem!

If a stud splits apart when folding it, that's not the end of the world. Because the studs are held together both by the rack rail and the nut, you can usually just keep using a stud that has split apart. I'd advise that you pay attention to the alignment before you start tightening the nut, though. If you want to avoid the studs splitting apart, use a more compliant material. I print mine in PLA, and I've actually never had one fall apart, but it can definitely happen. To test your material, simply grab a bit of filament and bend it sharply with your fingers 90 degrees one way, then the other way. If the end snaps off, that filament is too brittle. Some say you can dehumidify the filament back into life, but I'd suggest using that filament for something decorative instead.

The tolerances relatively tight on these. Nothing crazy, but everyone has a different setup and fitment issues can arise. If that happens, first try a standard print profile in your slicer with no tweaks other than printing with at least 3 walls. If you're still having issues, you'll have to tweak the scaling of the parts slightly. Use the rack rail as a reference and figure out if the studs are too big or the nuts are too small. Only scale up or down the “thickness” of the part, not the length. And please notify me so I can see if there are any trends with one particular dimension causing trouble. I might also publish a loose fitting version at a later point, but that would be somewhat detrimental to strength, so we'll avoid it if we can.

The threads and split design are inspired by Multiboard by Jonathan Kobylanski. At first glance, these threads might look compatible with the Multiboard threads, but that's a trap.