3D Printed Nut too small for Threaded Stud

[snowflake6515]

I am struggling to model a M30 1.5 nut to fit a previously modeled and printed stud.  Invariably, Fusion 360 resizes the nut's cylinder hole to match the selected size (M30 1.5, in this case.)  The resultant nut is too tight to fit on the stud.

The 3D printed stud works with the nylon nut that came with a part to hold PLA filament  I needed one longer, so I modeled it, it printed fine, and the supplied nut fits perfectly.  I cannot create the matching M30 1.5 nut.  I was able to follow the "Intersect" video to make chamfered corners, but nothing I do creates a slightly bigger opening.

Am I missing something?  I am using "Modeled", both ISO Metric and ANSI Metric, but no joy.

Thank you.

Michael (hobbyist)

[TheCADWhisperer]

Can you File>Eport and then Attach the *.f3d file and the resulting *. still file here?

[etfrench]

This may work for you:

I just used an arbitrary number for the shell thickness.  You'll need to experiment to determine the best size.  Printing the nut 2mm thick would be an economical way to test.

Note: The threads in Fusion 360 are created to the tolerances in the specifications.  Unfortunately, most 3d printers can't print to those tolerances.  However, it may be better to spend more time calibrating your printer than modifying the Fusion 360 models.

[filipmatyja]

Hi Michael,

It's good to double check tolerance class between your models of nut and stud. You might find them to be too perfect to fit each other in real life. Give them some space and try again.

The other problem might be with your machine. Create simple shapes that are easy to measure, make them with different speeds or set ups of the machine. Then measure all main geometries: length, thickness, squareness, diameters. 

The machine will always create imperfect part, you just need to know how bad/good it is. 

[etfrench]

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@filipmatyja wrote:

It's good to double check tolerance class between your models of nut and stud. You might find them to be too perfect to fit each other in real life. Give them some space and try again.

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That is the problem.  Fusion 360 doesn't expose an easy way to adjust the tolerances on threads.  You can't give them space.

[filipmatyja]

Hi @etfrench, 

so what does this option do in thread menu?

According to sandvik it should give you normal or very loose fit between nut and stud. Am I right?

Cheers,

F.

[snowflake6515]

I'm not sure what a "still" file is (.stl???), but the first file is the
longer filament support and works great with the original nylon nut.

The second file is the nut that I created so I could keep the original nut
with the original part. It is this nut that keeps coming out too small.
The diameter of the sketch is too large; part of my trying to see if I could
get more tolerance. No joy.

These are the second parts that I've created with Fusion 360; still
learning, obviously.

Thank you.

Michael

[etfrench]

Depends on if it's available

[TheCADWhisperer]

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@snowflake6515wrote:
I'm not sure what a "still" file is (.stl???),

Michael

---

Sorry  ~  texting from iPad.

I’ll give it a look in the morning  

[TheCADWhisperer]

Well, it is now morning and I still don't see any *.f3d or *.stl file attachment?

[snowflake6515]

I attached the files to the earlier post, but they clearly did not show up.

I am attaching three (cannot see how to attach a fourth file): f3d files for extended support and nut and the stl file for the nut.

I kept playing with the hole diameter for the nut before I finally realized that Fusion 360 was automatically resizing the hole to correspond to the M30 1.5 selection.

If the attachments do not come through, this time, then I'm stumped.

Thank you.

Michael

[lichtzeichenanlage]

You can offset set faces to flatten the angle of the thread. This could be done by using the press pull command. Why are adjustments needed? Consumer grade 3d printers are not 100% precise. 

This is an example what you can do. You might not to do both actions - just play with the press pull command and do some test prints.

[TheCADWhisperer]

I think I can significantly improve your technique, but I am a bit tied up today.  Check back tomorrow.

One thing for sure - in addition to clearance, I would add Chamfers for lead-in/lead-out of the thread.

[snowflake6515]

Wilco.  I am unsure of the amount of chamfer to use, but as the thread pitch is 1.5MM, I might start with 0.5MM chamfer on both sides.

Thank you.

Michael

[WyzeOwl · Accepted solution]

I have found that even with a calibrated printer and fine tuned print process, sometimes the fastest way to get a nut to fit a stud is to scale one or the other in the slicer. Do you have a vernier? (very inexpensive digital calipers can be found on Amazon). Measure the diameter of the nut ID and compare that the what should be the tap hole diameter. Hole ID for the nut should be 28.5mm. Once you know the actual ID and the theoretical ID you should be able to divide one by the other to get to a scaling factor in the print program and voila. Without measuring, you could do this empirically by scaling the nut until eventually it fits. Keep in mind that a small increase in diameter on a thread is a big change in fit. Tool loose and the nut won't stay put. What software are you using to do the prints?

[snowflake6515]

I am using the Cura software package to convert STL files into GCODE; came with the printer.

I like the idea of scaling; will take a look at that aspect after I finish printing a part with push/pull on the thread faces as suggested, earlier.  I already had started that printing before receiving the suggestion to chamfer the hole lead in/out edges; that will be next.

I am still very new at 3D modeling and printing; previously used Sketchup, but an acquaintance strongly recommended Fusion 360 and I am so glad I switched.

If I can figure out how to get the nut to work, then I won't hesitate to tackle the next project.

Thanks to all for the suggestions.

Michael

[TheCADWhisperer]

Scaling will change the thread Pitch.

It is better to add clearance to account for 3D printing not being a particularly precise manufacturing process - you do not want to alter the Pitch.

[henrycasson]

you can scale an STL in Netfabb, non uniformly. I would experiment with scaling in X and Y, say 103 %, leaving Z the same to try to preserve the thread pitch.

[snowflake6515]

I deliberately only scaled X and Y figuring that, by leaving Z alone, the pitch shouldn't change.

I have a new nut printing, now, with a scale factor of 1.015 and I'll see how that goes.

I wish that there was a way in Fusion 360 to loosen ("Add Clearance"); I thought that the "CTRL/CMD" popup on thread tool might be a way. but that only changes major diameter...

I had some trouble adding a filet to the leadin/leadout; it appears that I had to do it PRE-thread tool as POST popped up with errors.  The amount of chamfer, even using 0.1MM, appears excessive, IMHO.

Thank you.

Michael

[henrycasson]

I agree that the threading tool needs some more flexibility, and also the helix tool. We just have to wait and put in our suggestions. My intuition is that you will need to scale larger, but we’ll see.