Newbie to using an X1C, made and printed # 40 designs, I start to print designs including nuts and threaded hole in PETG.
Last try was M20 hole and nut.
My issue is that if I design a nut and threaded hole ( Autodesk Fusion 360), they won’t fit together. I learned from other threads to adjust the slicer to avoid crossing walls, inner/outer wall printing order, reduce printing speed, select fine layers, even tryied 100% infill, but it’s still not working, the printed screw does not fit into the nut. It requires very significant file work on both the screw and nut to make them work together, roughly removing 1mm diameter on each.
I probably missed some important point to make it work, help needed !!
Thanks,
Daniel
You have to give the thread a small offset. So far I have always done quite well with 0.15mm larger. However, I have only ever printed one of the two sides (nut or screw) and used a metal part as a counterpart. You’ll have to see if you need to offset both parts if you print them both.
Different materials behave differently and may result in models that don’t fit together as expected.
I printed a model that many have successfully printed in materials like PLA, PETG, and ABS/ASA, but when I printed it in PAHT-CF, the fit was extremely tight — almost too tight, to be honest.
Make sure to account for your printer’s precision and the material’s shrinkage when aiming for a perfect fit, especially for things like bolts and nuts.
As a general guideline, adding a clearance of 0.1–0.2 mm in your CAD model for most 3D printing materials helps ensure a proper fit.
I typically design with a clearance of 0.20mm and ensure all overhangs are 30 degrees or more. When printing threads use the 0.16mm High Quality profile since it offers both slower print speeds and better overhang performance due to the shorter layers.
I could explain how to design a nut and bolt so it works when printed.
But someone already made it much easier for you
It is not only the design that matters but also how you print it.
All filaments, even PLA curl up when trying to print fine threads on a bolt standing upright.
Than makes the bolt bind in the nut due to the deformations.
As a rule of thumb I don’t bother printing anything smaller than M6 and for the 0.4 nozzle I stop at M8.
I use several methods to print nuts and bolts.
Large enough nuts I print upright and with a fine layer height.
The curling up in a nut is not as bad as for a bolt as it is internal threads.
The bolts I prefer to cut and slice a bit.
Either printed laying flat and with a bit of the top and bottom part of thread removed they still fit and work fine but have no problem being printed.
A split design as offered by the generator works well too but can be tricky as the two halves tend to sheer out and cause binding.
I usually include a little botch to prevent this if it is bolts that need frequent removal.
If you have time I highly suggest watching this video. The TLDR is if you are designing your own nut/bolt and threaded hole and you don’t care about a specific size like M8 or whatever this is 100% the route to go. Most of the things I design use Clocksprings Method for nuts. It’s flawless and works at every size I’ve ever tried. You can check clockspring out of patreon or printables. Or you can check out some of my models if you want to see it in action.
Honestly I get upset when I print or pay for models where the threads suck.
If you have designed the threads with at least a small amount of clearance, try printing it again but this time reducing the filament flow rate by 0.05 until it becomes loose. Filament flow highly varies even from filaments of the same brand. I suggest trying this out first without having to re-design everything.
It’s because the threads in Fusion are real threads designed for metal bolts and such, which don’t translate very well into the 3d printed world. There are a couple threads pitches and sizes that are mediocre best when printed, but for the most part you are much better off making your own from scratch. I sketch mine out and use the sweep and coil tool for the guide rail and I have had really good results doing it that way.
Fusion thread tool is designed for CNC machining to use with thread cutting tool like this
or this
A good CNC milling machine can do high accuracy of 0.001mm for each step over X, Y, Z axis.
The problem with 3D printing is, you can’t have good control over dimension of the print or it is just tedious to set custom configuration to the slicer for each every print.
There would be option to choose for slicing tolerance: middle, exclusive, inclusive (as picture below). Normally default option is middle, but still if you put two staircase shapes next to each other, female and male, they won’t fit.
Note: 0.200e → make the external thread diameter smaller by 0.2mm
You just have to do trial and error to find correct tolerance. For me I just do 0.2e for external thread and 0.2i for internal thread, that is to match with 0.4mm nozzle diameter.
Tip: just go to fusion market place and install fusion plugin Threadkeeper. It will help you to install new custom threads and maintaining custom threads after fusion update or fresh install.
Just in case someone really wants to do all this the good old manual way…
Long and boring, prefer to use plugins ;)
If you want to create threads for printed parts but have no access or interest in Fusion…
Literally any CAD program can be (ab)used to create threads from scratch.
Like by creating a helix with a matching diameter to then extrude the thread profile along it’s path.
The thing that often keeps users from having good results is what is seen on the screen when creating nuts and bolts.
A gap can look huge on the screen and unless measured one might never realise this huge gap is less than 0.1mm.
Especially when it comes to a more diagonal gap things can get tricky.
When creating a thread from scratch I consider the required diameter and use case to find a good pitch.
For example at 20mm diameter a 3mm pitch works just fine if printed in 0.15mm layers or 0.2mm and slow.
One of the biggest hurdles for many people is the actual shape of the thread.
Metric bolts for example come with a 60º slope angle, or 30 above and below the centre line.
If you than have a pitch of just 1mm you really don’t need a calculator to realise that even 0.1mm layers would still make this painful to print.
It is not the fine details but the fact that this ongoing spiral overhangs WILL start to curl up, ruining the profile.
With no need to mate with a real world nut or bolt you can create a ROUNDED thread profile.
Like starting with a half circle and pulling it to an elliptical shape.
The stick with the 3mm pitch one could think a 3mm wide (vertical at the base) thread profile works great.
Until you start to extrude it and see that it leaves no gap.
Not a problem if you want to create a nut by simply enlarging the bolt to subtract it from a block for the nut but it really can mess up things.
Far easier is to create a match for the shape you plan to extrude and to factor in a GENEROUS gap.
Especially if the goal is to have it printable on many printers even if not 100% calibrated by newbies.
For a 3mm pitch a 2.5 to 2.8mm thread profile at the base is a nice start.
If you form an ellipse from there you can literally see when it goes too wide.
Say around 30 layer while printed and those ‘slices’ result in steps.
2 to 2.5 poking out is good and mean you can mirror a matching shape with no issues fitting it into the pitch.
How to determine the right tolerance/gap when designing the thread?
If for those tolerace test prints you worked out you need at least 0.12mm gaps in order to get a cylinder into a matching hole then you ONLY have the horizontal gap covered.
The vertical gap size is a factor of layer height, filament properties and thread shape.
Hence the problem with printing real world threads for smaller nuts and bolts.
We can’t print smooth slopes, we can only produce steps by printing in layers.
These steps spin around when getting parts together and if the gap is too close they will start binding.
Good plugins take care of all this guesswork but not everyone has them available for those tasks.
If you start with a nice gap for the profile in the pitch the vertical gap is not really that vital any more
The fit does not come from tight fitting shapes but from those shapes being able to move freely - the lock in place once tight.
The only thing to be aware of is the slope angles.
If your vertical gap is less than your established horizontal gap+20% things might bind up.
How to create those treads as a keeper to get different lengths when required?
I do this simply by cutting a slice with the same height as the pitch.
This way they can be stacked up and joined with ease and if you did not go overboard with details of the geometry you won’t even get manifold problems.
Create a top and bottom part where you created a nice taper for easy fitting and you can create any length needed.
Scaling threads…
Let’s say you really started from scratch and without fancy tools and plugins.
Not just that but you created a thread that works and looks great with a diameter of just 10mm because you were testing things
What a bummer when you scale it up and it all goes loose and wobbles around…
When scaling the tolerances are affected as well.
Scale down and those vital gaps shrink away, scale up and they grow too big.
There is a little cheat I sometimes use that relies on subtracting both the nut and the bolt thread from another solid to only get the gap between them.
Cutting that in half lengthwise and using just that face gives you a gap profile to work with.
What’s the difference?
Make a copy…
Now scale one to get the ID/OD of the thread you need.
Assign this scale profile for either the nut or the bolt.
The copy is scaled to give you a matching gap - so yes it will be out of specs so to say.
Works great when trying to enlarge, so it is best to start with a small design rather than a huge one.
Pay attention to how you enlarge!
There is usually the option to do this based on the centre or based on the opposite site - always work centre based!
Best however is if you kept the original sketch for your thread profiles to be extruded.
Works the same way to determine the factors but saves the steps to create a slice from an existing 3D model.
