ISO Metric Trapezoidal Threads: Fusion models 60° angle instead of 30°

[Anonymous]

Hi,

recently I needed to apply a simple "ISO Metric Trapezoidal Thread" with the thread tool onto a cylinder.

For this I used a modeled TR12x3 thread. However, the model in Fusion does not look at all like the piece of trapezoidal thread that I have here. Trapezoidal threads normally have a 30° angle, not the 60° angle that Fusion creates.

Here you can see the difference between the thread Fusion created and the ISO 2901-2904 (DIN 103) norm:

I use Fusion version 2.0.2321.

Any help would be highly appreciated!

Thanks.

[Beyondforce]

Hi @Anonymous,

Maybe this can help: https://www.youtube.com/watch?v=IpfPoA6_OWM

Cheers / Ben
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[Anonymous]

Hey Ben,

thanks for the quick answer and your workaround video. I guess I will model the threads with your method until this bug is fixed.

Have a nice weekend,

Folke

[Beyondforce]

Hi Folke,

Happy to help and let me know if you get into "trouble" 😉

Cheers / Ben
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[JDMather]

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@Anonymous wrote:

... until this bug is fixed.

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How is standard 60° threadform a "bug"?

[HughesTooling]

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@Anonymous wrote:

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@Anonymous wrote:

... until this bug is fixed.

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How is standard 60° threadform a "bug"?

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Did you see it's for a trapezoidal thread? The standard for ISO trapezoidal threads is 30° inclusive.

http://www.amesweb.info/Screws/MetricTrapezoidalScrewThreads.aspx

Mark

Edit just noticed the ACME threads are drawn correctly at 29° so there shouldn't be too much of a problem fixing this.

[Anonymous]

Hi @JDMather,

metric trapezoidal threads are very similar to ACME threads - they just have a slightly different thread angle and, of course, use a metric diameter/pitch combination (i.e. TR12x3 has an OD of 12mm and a 3mm pitch). Metric uses a 30° thread angle whereas ACME uses 29°.

The standard that defines this is DIN 103 (respectively ISO 2904). Here you can see what I mean: http://www.roymech.co.uk/Useful_Tables/Screws/Trapezoidal.html

In Fusion, when I create an "ISO Metric Trapezoidal Thread", the created thread profile has a 60° thread angle, but it should have a 30° thread angle. I have a piece of trapezoidal thread laying around and I can easily see the difference.

The "standard 60° threadform" is only used for standard metric screws, i.e. M6, M8, M12 etc. (DIN 13, ISO 1502)

I know it is a bit confusing, but if you have any questions, feel free to ask them - I will try to explain it as best as I can.

Greetings, Folke

[JDMather]

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@Anonymous wrote:

....In Fusion, when I create an "ISO Metric Trapezoidal Thread", .....

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I didn't realize that this threadform standard was already built into Fusion - I thought you were requesting an enhancement addition to the standards.

Carry on....!

[rishabh.bisht]

This issue should be fixed with the April 2019 release.

[HughesTooling]

This isn't fixed, you might have corrected the angle but the form is totally wrong.

Obvious the threads on the right have the wrong form, the one on the left is an acme for comparison.

I've made another post about this and the fact all metric threads are constructed incorrectly in Fusion here.

Mark