Screws and Bolts - When do you print your own or use metal ones?
 
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Tango
(@tango)
Estimable Member
Screws and Bolts - When do you print your own or use metal ones?

I have had some situations where I had to add threads to something like a pipe coupler and just screw it into another part. I've also seen a few designs that use printed screws and bolts. On the one hand, it can be a pain to print screws (and make holes with the corresponding threads), but on the other hand, when sketching some ideas, I've found a few situations where it made more sense to print a screw or bolt than to use a commercially made metal one.

Do you ever make printed screws and, if so, when do you find it makes more sense to print out a screw than to use commercial metal screws? And is there any information on just how reliable a printed screw can be? (I figure one factor would be the strength of the threads, which could vary depending on the thread size.)

Posted : 07/01/2024 7:37 am
adesir
(@adesir)
Reputable Member
RE:

It's not about screws, but about threads, but that gives some ideas:

From my little experience: metal screws and inserted nuts for small diameters. Printed ones for large diameters and light loads.

This post was modified 3 months ago 2 times by adesir
Mes modeles publics
Posted : 07/01/2024 8:27 am
languer liked
John
 John
(@john-6)
Reputable Member
RE: Screws and Bolts - When do you print your own or use metal ones?

I wouldn’t print a threaded bolt less than 12mm diameter but I print threaded sockets for metal screws down to 3mm. Whilst threads are not fully formed you can run a tap through with fingers. 

i3 Mk3 [aug 2018] upgrade>>> i3MK3/S+[Dec 2023]

Posted : 07/01/2024 8:32 am
languer liked
JP Guitars
(@jp-guitars)
Estimable Member
RE: Screws and Bolts - When do you print your own or use metal ones?

I'm similar although I would want an extruded thread to be bigger than 12mm, 20ish or more. And I don't bother threading small holes, I just screw the bolt straight into the plastic - works well providing you don't need to remove and reinsert the bolt

Posted : 07/01/2024 10:15 am
_KaszpiR_
(@_kaszpir_)
Reputable Member
RE:

If something should be sturdy then normal bolts + washers + nuts, it requires extra space around objects but this is most reliable one.
Everything else will wear out over time because of the tension and the surface area between objects.

I do not print threads if I can avoid it, they are really brittle and work only in certain situations - that's why there are some few full printable vice models but they recommend not to overtighten them oterhwise they snap, AFAIR at least M8 is okay for 3D print but still may be brittle.

Hot inserts or print-in-place nuts (pause print, insert nuts) are AFAIR the best option if you want to have best experience.

See my GitHub and printables.com for some 3d stuff that you may like.

Posted : 07/01/2024 12:24 pm
Tango
(@tango)
Estimable Member
Topic starter answered:
RE: Screws and Bolts - When do you print your own or use metal ones?

In my case, I was working on a connector for a flexible duct, which was 100mm (4") in diameter. So the threads had a large diameter and I used a larger size for the thread, so it wouldn't be something thin that would easily mess up.

Unless I'm working on something that is never intended to be taken apart once it's assembled, I'm not going to make printed threads for a metal screw and I'm going to avoid using self-taping screws. I'm working now (I have another thread about this) on test prints for heat set inserts, slots for square nuts, holes for "normal" nuts and for t-nuts. I figure using metal nuts with a metal screw or bolt is going to work much better than using printed threads with metal screws.

I do have on situation where I might need an adjustment screw and I am thinking of using a printed thread for that for multiple reasons. I may switch to a metal screw for that, but it depends on just how things fit together in the final design.

I was thinking, overall, that printed threads, unless they are larger threads, would likely not hold up to much force or weight. I was just wondering what others had decided from experience.

Posted : 07/01/2024 5:16 pm
Michael Phillips
(@michael-phillips)
Active Member
RE: Screws and Bolts - When do you print your own or use metal ones?

I print threads all the time but not for my climbing gear! I made an OpenSCAD library to make metric threads. The diameter for threads in the spec is a range. So I use the largest in spec diameter for internal threads and the smallest in spec diameter for external threads as a good starting point for fit tolerance. I have only had to change the tolerances when mixing metal and printed parts. I almost always use PETG for threaded parts because it has good layer adhesion. I have also played around with printing threaded rod horizontally with a small flat side and they seem to be really strong under tension not that I did any scientific testing or anything like that.

Here is a little remix I did of Yet Another Machine Vice to make a mount for a RioLink camera. I shortened the vice and used M8 bolts to attach the tilting part. There is an M8 shoulder bolt for the pin in the hinge and on top are threaded M4 holes for a couple of printed M4's, not shown, to attach the camera. The M4 were just because I could and the 2.5mm hex drive stripped out pretty easy so I had to tighten with pliers.

My machines: Prusa i3MK3S+ with MMU3 and Sienci LongMill 30x30 CNC router/laser

Posted : 07/01/2024 6:16 pm
Diem
 Diem
(@diem)
Illustrious Member

I have experimented down to M2.5 - don't bother.  The smallest for an actual project was M3 and that was mostly as a showoff, in practice that worked much better with M3 female threads and metal screws.

M3 printed female threads with metal screws is a genuinely workable option for many small PLA projects but remember tht PLA will evade pressure and don't overtighten.  You also have the option of unthreaded holes and self-tapping screws, a better option for PETG; this works down to very small diameters.

My experiments with printed nylon threads have all failed.

I have had much more success with 5.5mm diameter threads at 2mm pitch - one of my projects that makes extensive use of them is here:

https://www.printables.com/model/255791-basic-walker-walking-construction-toy

- You still have to be gentle with them but for some projects fastners that break before any critical parts and which can be replaced easily are an advantage.

As you go up in size printed threads become more reliable, 1mm threads are always problematic but if you are designing the screws you can enlarge them to suit.

Cheerio,

Posted : 07/01/2024 7:09 pm
fuchsr liked
JP Guitars
(@jp-guitars)
Estimable Member
RE: Screws and Bolts - When do you print your own or use metal ones?

Thomas Sanladerer published a video yesterday comparing the strength of various thread methods which was interesting:

The failure modes was different to what I had expected.

Posted : 07/01/2024 11:58 pm
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