How big should the rivets be?

[ariyob09]

So, basically, I am trying to 3d print a butterfly knife trainer. I have modeled 2 rivets that will go into the top 2 holes. I don't know exactly how much smaller I should make the rivets since I want them to allow the butterfly knife to have free and fluid movement but I don't want them to be too loose. I also don't know how much smaller the second piece of the rivet should be. Currently, the holes are .25 inches, the top pieces for the rivets are .245 inches and the bottom pieces for the rivets are .24 inches. Is this good or should I make them bigger or smaller? I am relatively new to fusion 360 so I'm sorry if this question is really basic this is only my 3rd week using the software.

[TrippyLighting]

This isn’t really a Fusion 360 question. For 3D printing (as opposed to machining) clearances have to be modeled. What that clearance needs to be, depends on a given 3D printer. I’d make a test print and then size holes and rivets according to findings. Smaller differences can be ‘adjusted’ with sand Paper.

[g-andresen]

Hi,

Keep in mind that several influencing factors (material, extrusion volume ...) play a role.

günther

[TheCADWhisperer]

---

@TrippyLighting wrote:

 For 3D printing (as opposed to machining) clearances have to be modeled.

---

For machining - clearances have to be modeled too.  (They would just be less and presumably more precise.)

We cannot create perfect geometry.

And even if we could manufacture perfect geometry a 10m pin will not turn in a 10mm hole.  The atoms on the 10mm circle (cylinder) would have to give way to each other.

Edit:  Almost forgot.  If this might be mass produced in the future - consider standard sizes for rivets and drills.  Don't make just any size (especially Holes).  Standard tooling.

[TrippyLighting]

---

@TheCADWhisperer wrote:

For machining - clearances have to be modeled too. 

---

Can you explain how you define the term Clearance?

[TheCADWhisperer]

---

@TrippyLighting wrote:

---

@TheCADWhisperer wrote:

For machining - clearances have to be modeled too. 

---

Can you explain how you define the term Clearance?

---

In this case:  The difference in size between a cylindrical hole and a cylindrical shaft such that the parts will freely rotate without binding when assembled.  As indicated in previous response - this condition cannot be met with for example a Ø10 hole and a Ø10 shaft.

There are entire Standards published on this topic.

https://en.wikipedia.org/wiki/Limits_and_fits

https://en.wikipedia.org/wiki/Engineering_fit#Clearance_fits

[TrippyLighting]

---

@TheCADWhisperer wrote:

---

@TrippyLighting wrote:

---

@TheCADWhisperer wrote:

For machining - clearances have to be modeled too. 

---

Can you explain how you define the term Clearance?

---

In this case:  The difference in size between a cylindrical hole and a cylindrical shaft such that the parts will freely rotate without binding when assembled.  As indicated in previous response - this condition cannot be met with for example a Ø10 hole and a Ø10 shaft.

There are entire Standards published on this topic.

https://en.wikipedia.org/wiki/Limits_and_fits

https://en.wikipedia.org/wiki/Engineering_fit#Clearance_fits

---

Right! The one I am mostly familiar with is the Einheitbohrung un Einheitswelle. Those tolerances are usually not modeled. Design is to nominal dimensions, e.g. the Bohrung (hole)  and the Welle (shaft) are modeled with the same diameter. The tolerances are then defined on the manufacturing drawing.

Those tolerance limits then result in clearance fit, transition fit, or interference(press) fit.

In case of a clearance fit, there is a min and max clearance. But again, that would not be modeled!

That is what I was referring to.

I am glad we did not have to dive into quantum mechanics 😉

[ariyob09]

Here you go 🙂

[TheCADWhisperer]

---

@TrippyLighting wrote:

---

Design is to nominal dimensions, e.g. the Bohrung (hole)  and the Welle (shaft) are modeled with the same diameter. The tolerances are then defined on the manufacturing drawing.

But again, that would not be modeled!

I am glad we did not have to dive into quantum mechanics 😉

---

Yes, that is how we did it in the last century, but in this century with Model Based Definition - there might not even be 2D drawing documentation.

It true-to-life modeling we can dive into the quantum mechanics with Interference Analysis, Tolerance Stack-up Analysis, Dynamic Simulation (contact forces and friction) 3D Annotation, and if we do create a 2D drawing we can retrieve (promote) the model dimensions including tolerance specification directly from the model into the drawing.  The model becomes our single source of truth.

https://en.wikipedia.org/wiki/ASME_Y14.41

[TrippyLighting]

---

@TheCADWhisperer wrote:

---

...

It true-to-life modeling we can dive into the quantum mechanics with Interference Analysis, Tolerance Stack-up Analysis, Dynamic Simulation (forces and friction) 3D Annotation, and if we do create a 2D drawing we can retrieve (promote) the model dimensions including tolerance specification directly from the model into the drawing.  The model becomes our single source of truth.

---

The more I read your comments, the more I realize how far the gap between Autodesk Inventor Professional and Fusion 360 really is. I hope it wasn't too farfetched that you are referring to Inventor because you can certainly not do that (Model Based Definition) in Fusion 360.

Hell, almost 8 years in I can still not make a fully parametric component pattern.

[TheCADWhisperer]

---

@ariyob09 wrote:

Here you go 🙂

---

@ariyob09 

Your first sketch - Sketch4 is missing dimensions and showing a highlighted as unresolved issue.

What happened to the dimensions?

[TheCADWhisperer]

---

@TrippyLighting wrote:

---

Hell, almost 8 years in I can still not make a fully parametric component pattern.

---

After 8 years - Fusion isn't able to do what others could do 8 years ago, let alone what they are doing today.

Design Differently. 🙄

[ariyob09]

The only missing dimensions that I can see is the bottom which I filleted (sorry if that spelled wrong) after I extruded the sketch. I do not see anything for an "unresolved issue" anywhere on my UI. 

[TheCADWhisperer]

---

@ariyob09 wrote:

The only missing dimensions ...

---

I don't see ANY dimensions at all?

And missing Tangent Constraints?

[TheCADWhisperer]

---

@ariyob09 wrote:

I do not see anything for an "unresolved issue" anywhere on my UI. 

---

Yellow highlight - right there on your Timeline? 

What does Ctrl b (CMD b on Mac) return?

[TheCADWhisperer]

I think you will be OK on the pin depending on your printer, but not enough clearance on the head of the pin for the counterbore.

[TheCADWhisperer · Accepted solution]

BTW - Any time that you are tempted to use Move command you should STOP and ask questions here.  There is often a better technique.

This entire design could be done with a handful of sketches and significantly simplified process.

Do you want to learn how step-by-step?

[ariyob09]

I'm in 9th grade and using this software for school (paid for). There are going to be more tutorials as we go along but I have only been using this software for about 3 weeks or so. I appreciate the offer though, thank you for helping me with my problem!