Bug: Thread tool does not model the pitch diameter correctly

[HansenDK]

In short, I feel quite confident that the thread tool does not consider the pitch diameter stated in the thread XML files when modelling a thread.

I made another thread about it (https://forums.autodesk.com/t5/fusion-360-design-validate/does-the-thread-tool-generate-correct-thre...), but to be sure that I file this as a bug report, I duplicate the issue here.

Best regards

Jesper

[kelly.young]

Hello @HansenDK It appears that Fusion is driving the thread by:

• External Thread (P)
• Major Diameter Average (max+min/2)
• Minor Diameter Average (max+min/2)
• Pitch Width (P/2)
• Tip Width (P/8)
• Angle (60°)

If you are expecting the Pitch Diameter Average in the .xml to be fully enforced you will have an over constrained result.

Here is a screencast that hopefully explains the behavior a bit more clearly: 

Hope that helps!

Please select the Accept as Solution button if a post solves your issue or answers your question.

[HansenDK]

Hi @kelly.young

Thanks for the webcast. It did help me to understand that the thread tool for some reason enforces some of the profile parameters defined in the UTS - some but not all.

Unfortunately, to me it seems odd that the XML file includes the pitch diameter, when the tool does not use it. Instead the tool enforces some of the UTS definitions of the top and bottom of the thread basically (re)-defining the pitch diameter. In contrast, it is possible to change the angle of the thread in the XML file, which would then go against the 60 degrees defined by the UTS, so the tool doesn't really conform to the UTS, if that was the intention.

Having the possibility to define the angle, the major, minor and pitch diameter in the XML file is ideal - without these "hidden constraints". It enables the user to define any thread - and not just threads conforming to (some of) the UTS.

I suggest that these hidden constraints are removed from the thread tool, so that the thread tool models threads entirely as defined by the XML file.

Best regards

Hansen 🙂

[paul.clauss]

Hi @HansenDK

Thanks for posting! I meant to comment on this thread on Monday, but it looks like I might have forgotten. I've logged FUS-38848 with the development team to look into why the XML shows a different pitch diameter than the modeled threads - we appreciate you bringing this to our attention.

[HansenDK]

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@paul.clausswrote:

Hi @HansenDK

Thanks for posting! I meant to comment on this thread on Monday, but it looks like I might have forgotten. I've logged FUS-38848 with the development team to look into why the XML shows a different pitch diameter than the modeled threads - we appreciate you bringing this to our attention.

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Hi Paul

As far as I can see, the odd behaviour remains in the April update. Any news on FUS-38848?

Thanks 🙂

[paul.clauss]

Hi @HansenDK

Thanks for reaching out! This issue is still being investigated by the development team - it was not resolved in the recent updates. We appreciate you bringing this to our attention and the development team will be continuing to investigate a fix. 

I'll keep you updated here with any new information I have to share.

[HansenDK]

Hi

The bug report just celebrated it's one year anniversary 🙂 Has the bug been fixed by now?

[paul.clauss]

Hi @HansenDK 

Thanks for reaching out. This ticket is still unresolved and I have reached out to the development team on the ticket to ask about future plans and relay your comments. Please feel free to reach out whenever you have questions.

[HansenDK]

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@paul.clauss wrote:

Hi @HansenDK 

...I have reached out to the development team on the ticket to ask about future plans and relay your comments...

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Hi @paul.clauss 

So, what did the team say? 

[paul.clauss]

Hi @HansenDK 

Thanks for the response. The team is still investigating - I've reached out for another update.

Why are you creating custom threads through the XML files? Since this ticket was originally logged, quite a few thread types have been added to Fusion 360. Knowing why the XML files are still being used to create custom threads may help us get this issue prioritized by dev.

[HughesTooling]

I made a thread back at the beginning of 2017 about the thread form for female threads being totally wrong, that's still not fixed so don't hold your breath on getting this fixed.

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@paul.clauss wrote:

Hi @HansenDK 

Why are you creating custom threads through the XML files? Since this ticket was originally logged, quite a few thread types have been added to Fusion 360. Knowing why the XML files are still being used to create custom threads may help us get this issue prioritized by dev.

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Where does it say anything about custom threads, the bigger problem is the standard generic threads are wrong!

Mark

[HansenDK]

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@paul.clauss wrote:

Hi @HansenDK 

...Why are you creating custom threads through the XML files?...

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I'm defining (read: I would like to define) custom threads optimized for different manufacturing processes - for example FDM printing.

[paul.clauss]

Thanks @HansenDK and @HughesTooling ! I've relayed your comments to the development team.

[HughesTooling]

@paul.clauss  If you need info for the dev to prioritise fixing this here's my thoughts.

I think whoever worked on this originally has very little practical experience working with threads in the real world and has made the wrong choices about what's important. If you look at the total tolerance for the diameters you'll see the Pitch Diameter is the tightest, this should tell you which is important!

                                Max                 Min             Total Tolerance

Major Dia            9.968                9.732                      0.236

Pitch Dia             8.994                8.862                      0.132

Minor Dia            8.307               7.938                       0.369

 @kelly.young's Video also shows a lack of understanding of the real world, the widths of the flats at the peak and trough are not important and can still be maintained within the tolerance if the pitch diameter is correct.

You can see in this image the pitch diameter is correct and the widths at the peak and trough are both still within tolerance, these widths should not be used to drive the sizes for the thread as they are the least important sizes.

As the total tolerances are different for each diameter if you use the median then apply the width of flat for major and minor diameter you're going to end up with the pitch diameter too big, the most important diameter!

I've included my design used for the above picture.

Mark

[HansenDK]

Hi

Now, almost five years after reporting this, I am curious to know if this has been fixed yet (?).

BR

Jesper

Denmark

[seth.madore]

Sadly, no, it's not risen to priority with the development teams. However, there is some internal renewed interest in significant threading improvements, and I do believe that this topic is in the bucket of improvements.