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Custom Threading XML - Pitch is wrong

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Message 1 of 19
sidhantgupta
1576 Views, 18 Replies

Custom Threading XML - Pitch is wrong

Hello,

Similar to my other post where I specifically called out issues with ThreadType, I am also noticing issues with Thread Pitch.

 

I followed this tutorial: https://knowledge.autodesk.com/support/fusion-360/troubleshooting/caas/sfdcarticles/sfdcarticles/Cus...

 

My XML:

<ThreadType>
	<Name>Test Custom Thread</Name>
	<CustomName>Test Custom Thread</CustomName>
	<Unit>in</Unit>
	<Angle>60</Angle>
	<ThreadForm>1</ThreadForm>
	<SortOrder>1</SortOrder>
	<ThreadSize>
		<Size>2.20-A</Size>
		<Designation>
			<ThreadDesignation>TestThread</ThreadDesignation>
			<CTD>TestThread</CTD>
			<TPI>6.62</TPI>
			
			<Thread>
				<Gender>internal</Gender>
				<Class>2B</Class>
				<MajorDia>2.221</MajorDia>
				<PitchDia>2.149</PitchDia>
				<MinorDia>2.075</MinorDia>
				<TapDrill>2.048</TapDrill>
			</Thread>
		</Designation>
	</ThreadSize>
	
</ThreadType>

 

As you can see I am looking for a thread pitch of ~0.151 inches (1/0.151 = ~6.62 TPI). What I get is 0.167 pitch or ~6 TPI. Why?

 

sidhantgupta_0-1590187363022.png

Files attached to replicate issue. I am on Windows 10 running Fusion 2.0.8407.

18 REPLIES 18
Message 2 of 19

I answered in your other post, reply below as well.

 

Looks like removing the thread form from the XML fixes the problem. Seen this bug in the past, thought it got fixed. @jeff_strater  is this bug logged?

 

Modified file attached. Also looks like only whole numbers can be used for TPI, so 6.62 gives a 6.0 TPI. You can work around this using Pitch instead. So @sidhantgupta  You seem to have run into 2 bugs here. Attached file used pitch and gives the correct form and pitch of 0.151

 

 

<?xml version="1.0" encoding="utf-8"?>
<ThreadType>
  <Name>Test Custom Thread</Name>
  <CustomName>Test Custom Thread</CustomName>
  <Unit>in</Unit>
  <Angle>60</Angle>
  <SortOrder>1</SortOrder>
  <ThreadSize>
    <Size>2.20-A</Size>
    <Designation>
      <ThreadDesignation>TestThread</ThreadDesignation>
      <CTD>TestThread</CTD>
      <Pitch>0.1510574018126888</Pitch>
      <Thread>
        <Gender>internal</Gender>
        <Class>2B</Class>
        <MajorDia>2.221</MajorDia>
        <PitchDia>2.149</PitchDia>
        <MinorDia>2.075</MinorDia>
        <TapDrill>2.048</TapDrill>
      </Thread>
    </Designation>
  </ThreadSize>
</ThreadType>

 

 

With my modified XML I get this.

image.png

Mark

Mark Hughes
Owner, Hughes Tooling
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Message 3 of 19

@sidhantgupta  Thought about this a bit more and if you actually want sharp point then your major and minor diameters are wrong. To achieve sharp corners you need to calculate the major, minor diameters off the pitch and you need to be very accurate about this.

Here's how I constructed a sketch to calculate. When rounded to 3 places Fusion failed to create the thread!

Clipboard01.jpg

After updating the XML to a few more decimal places I get this. So there's no bug using Sharp as the thread type, @jeff_strater  still a problem with TPI though I think.

image.png

This is the XML I ended up with.

<?xml version="1.0" encoding="utf-8"?>
<ThreadType>
  <Name>Test Custom Thread</Name>
  <CustomName>Test Custom Thread</CustomName>
  <Unit>in</Unit>
  <Angle>60</Angle>
  <ThreadForm>1</ThreadForm>
  <SortOrder>1</SortOrder>
  <ThreadSize>
    <Size>2.20-A</Size>
    <Designation>
      <ThreadDesignation>TestThread</ThreadDesignation>
      <CTD>TestThread</CTD>
      <Pitch>0.1510574018126888</Pitch>
      <Thread>
        <Gender>internal</Gender>
        <Class>2B</Class>
        <MajorDia>2.2798</MajorDia>
        <PitchDia>2.149</PitchDia>
        <MinorDia>2.01818</MinorDia>
        <TapDrill>2.0</TapDrill>
      </Thread>
    </Designation>
  </ThreadSize>
</ThreadType>

Mark

Mark Hughes
Owner, Hughes Tooling
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Message 4 of 19

Wow! Thank you SO much @HughesTooling! You fixed both my issues and thank you for the education on calculating Major and Minor appropriately!

 

Could you please tell me how you knew to use <Pitch> and where such information is documented?

 

Sidhant

Message 5 of 19


@sidhantgupta wrote:

 

Could you please tell me how you knew to use <Pitch> and where such information is documented?

 

Sidhant


When I found TPI didn't work I remembered Fusion's metric thread XML files used Pitch so thought I'd try it in your XML file.

 

Mark

Mark Hughes
Owner, Hughes Tooling
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Message 6 of 19

Hello,

 

I'm working also on customizing some thread and I'm wondering if we can find any comprehensive informations about how to set MajorDia, PitchDia, MinorDia...

 

Is there any schema showing this with the relative formulas?

 

like D1=D-(1.0825xpitch) (where D is the nominal and D1 the inner diameter) in the cas of an ISO metric profile?

Message 7 of 19


@jean-michel_legoff  schrieb:

Hello,

 

I'm working also on customizing some thread and I'm wondering if we can find any comprehensive informations about how to set MajorDia, PitchDia, MinorDia...

 

Is there any schema showing this with the relative formulas?

 

like D1=D-(1.0825xpitch) (where D is the nominal and D1 the inner diameter) in the cas of an ISO metric profile?


In principle, yes.

 

The respective Norm of that thread gives the answer, but has to be bought.

If you search the Internet you generally get tables, where most of them only tell the nominal Diameters, but not the tolerances. Those ar typical - for bolts and + for Nuts relative to nominal diameter. You may find a table with the tolerances. The threads from the library in Fusion regularly use the mid diameter of the tolerance for a specific thread.

If you are very lucky, you find a document not only telling the values of a given size, but also the formular that creates it, without buying the Norm.

Like e.g. in the following video https://www.youtube.com/watch?v=TKyXV3r7MU8

This guy was lucky enough to find a site that tells  not only the values, but also the "creation formula" for UTS Threads.

Maybe this can help you to find values for your custom thread:

https://www.emuge-franken-bg.com/attachments/article/97/15%20Gewindetabellen.pdf

Maybe this helps you

 

Message 8 of 19
markusthur
in reply to: HughesTooling


@HughesTooling  schrieb:

@sidhantgupta wrote:

 

Could you please tell me how you knew to use <Pitch> and where such information is documented?

 

Sidhant


When I found TPI didn't work I remembered Fusion's metric thread XML files used Pitch so thought I'd try it in your XML file.

 

Mark


@HughesTooling 

I was running in a strange Problem those days, maybe you also know more about that, as I have the feeling its something similar as it was here, a little buggy in combination with doing something impossible.

 

I tried to create a thread similar to BSP G3/4-14, just fith a TPI of 12 instead of 14, So I copied the BSP.xml file, deleted everything from it, that is not a G3/4 thread, copied that thread section and changed the TPI to 12.

 

Result is, I get the thread as desired, but if I select formed, the thread is a trapezoid and not that rounded thing that A BSP should looklike.

Same if I do it for the just copied G3/4-14.

On the other hand, if I select the G3/4-14 from the standard BSPPipeThread.xml then the thread has those fancy rounded endings as a BSP Thread should be.(I asume WithWorth would be the proper selection for <ThreadForm>).

 

So I checked the standard file, It does not set <ThreadForm> as my custom as a copy also did not.

So I did set the value with the result, that I can see a change for selection 1 and 5 (sharp and squaric), but 0 and 7 (trapezoid and WithWorth) do result in same Trapezoid optics.

 

So I have four main questions:

Am I doing something wrong?

Is there a bug causing this?

How does fusion know for the standard BSP Threads, that they have the fancy rounding?

Do you know more?

 

 

 

From BSPPipeThreads.xml

<ThreadType>
  <Name>BSP Pipe Threads</Name>
  <CustomName>BSP Pipe Threads</CustomName>
  <Unit>mm</Unit>
  <Angle>55</Angle>
  <SortOrder>19</SortOrder>
....
  <ThreadSize>
    <Size>3/4</Size>
    <Designation>
      <ThreadDesignation>G 3/4-14</ThreadDesignation>
      <CTD>G 3/4-14</CTD>
      <TPI>14.0</TPI>
     <Thread>
        <Gender>external</Gender>
        <Class>A</Class>
        <MajorDia>26.299</MajorDia>
        <PitchDia>25.208</PitchDia>
        <MinorDia>24.117</MinorDia>
      </Thread>
      <Thread>
        <Gender>internal</Gender>
        <Class>A</Class>
        <MajorDia>26.441</MajorDia>
        <PitchDia>25.35</PitchDia>
        <MinorDia>24.3875</MinorDia>
        <TapDrill>24.5</TapDrill>
      </Thread>
      <Thread>
        <Gender>external</Gender>
        <Class>B</Class>
        <MajorDia>26.299</MajorDia>
        <PitchDia>25.208</PitchDia>
        <MinorDia>24.117</MinorDia>
      </Thread>
    </Designation>
  </ThreadSize>
...
</ThreadType>

 

 

 

 

 

<ThreadType>
  <Name>Custom BSPPT WW Test</Name>
  <CustomName>Custom BSPPT WW Test</CustomName>
  <Unit>mm</Unit>
  <Angle>55</Angle>
  <ThreadForm>7</ThreadForm>
  <SortOrder>19</SortOrder>
  <ThreadSize>
    <Size>3/4</Size>
    <Designation>
      <ThreadDesignation>G 3/4-14</ThreadDesignation>
      <CTD>G 3/4-14</CTD>
      <TPI>14.0</TPI>
      <Thread>
        <Gender>external</Gender>
        <Class>A</Class>
        <MajorDia>26.299</MajorDia>
        <PitchDia>25.208</PitchDia>
        <MinorDia>24.117</MinorDia>
      </Thread>
      <Thread>
        <Gender>internal</Gender>
        <Class>A</Class>
        <MajorDia>26.441</MajorDia>
        <PitchDia>25.35</PitchDia>
        <MinorDia>24.3875</MinorDia>
        <TapDrill>24.5</TapDrill>
      </Thread>
      <Thread>
        <Gender>external</Gender>
        <Class>B</Class>
        <MajorDia>26.299</MajorDia>
        <PitchDia>25.137</PitchDia>
        <MinorDia>24.117</MinorDia>
      </Thread>
    </Designation>
    <Designation>
      <ThreadDesignation>G 3/4-12</ThreadDesignation>
      <CTD>G 3/4-12</CTD>
      <TPI>12.0</TPI>
      <Thread>
        <Gender>external</Gender>
        <Class>A</Class>
        <MajorDia>26.299</MajorDia>
        <PitchDia>25.208</PitchDia>
        <MinorDia>24.117</MinorDia>
      </Thread>
      <Thread>
        <Gender>internal</Gender>
        <Class>A</Class>
        <MajorDia>26.441</MajorDia>
        <PitchDia>25.35</PitchDia>
        <MinorDia>24.3875</MinorDia>
        <TapDrill>24.5</TapDrill>
      </Thread>
      <Thread>
        <Gender>external</Gender>
        <Class>B</Class>
        <MajorDia>26.299</MajorDia>
        <PitchDia>25.137</PitchDia>
        <MinorDia>24.117</MinorDia>
      </Thread>
    </Designation>
  </ThreadSize>
</ThreadType>

 

 

 

I tested through values 0,1,5 and 7 for ThreadForm, but never got the fancy roundings as the BSP should have. I also tried to not set the value at all

Message 9 of 19
HughesTooling
in reply to: markusthur


@markusthur wrote:

@HughesTooling  schrieb:

@sidhantgupta wrote:

 

Could you please tell me how you knew to use <Pitch> and where such information is documented?

 

Sidhant


When I found TPI didn't work I remembered Fusion's metric thread XML files used Pitch so thought I'd try it in your XML file.

 

Mark


@HughesTooling 

 

I tried to create a thread similar to BSP G3/4-14, just with a TPI of 12 instead of 14, So I copied the BSP.xml file, deleted everything from it, that is not a G3/4 thread, copied that thread section and changed the TPI to 12.

 

 


 

Did you just change the TPI? Have you changed the major, pitch and minor diameters to match the different pitch as well? Did you try using pitch instead of TPI as well? I've attached a BA XML file that someone setup, it did work in the past and produced the Whitworth form, don't know if it still works.

 

I noticed the built in XML files don't specify the thread types as well, must be hard coded in the program with the standard files.

 

Mark

Mark Hughes
Owner, Hughes Tooling
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Message 10 of 19
markusthur
in reply to: HughesTooling



Did you just change the TPI? Have you changed the major, pitch and minor diameters to match the different pitch as well? Did you try using pitch instead of TPI as well? I've attached a BA XML file that someone setup, it did work in the past and produced the Whitworth form, don't know if it still works.

 

I noticed the built in XML files don't specify the thread types as well, must be hard coded in the program with the standard files.

 

Mark


I did two things:

For G3/4-14 i did change nothing, this is just plain copy of what is found in BSPPipeThreads.xml

For G3/4-12 i only changed the TPI. (as this is the idea of that spechial thread, having same measurements but less TPI or more Pitch.

And I added the <ThreadForm>7</ThreadForm> tag. (I also did try 1 and 5, those two lead somehow to the exspected result, sharp gets sharp within the boundaries you already described, and sqauric also gives some kind of a of thread different from a trapezoid. Doesn't make real sense, but is what this strange spec a 55° squaric thread has to produce :-))

 

Just 7 WithWorth behaves as if I would have set trapezoid.

 

I will try your suggestion to try Pitch instead, to evade this strange bug :-). No idea, what is so difficult in calculating 25.4 / x for a CAD Programm in oder to convert TPI to pitch 🙂

 

have a nice weekend and thank you very much.

 

 

Message 11 of 19
HughesTooling
in reply to: markusthur


@markusthur wrote:


I did two things:

For G3/4-14 i did change nothing, this is just plain copy of what is found in BSPPipeThreads.xml

 

For G3/4-12 i only changed the TPI. (as this is the idea of that special thread, having same measurements but less TPI or more Pitch.

 

 


Just changing the pitch will not work, the form will different. You will need the correct major, minor and pitch diameters or it will fail. This will be a bigger problem with the Whitworth form with the filleted points.

 

It's odd the exact copy fails. If you can't get this to work it would probably be best to start another thread and report the bug. I don't have time to experiment at the moment.

 

Mark

Mark Hughes
Owner, Hughes Tooling
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Message 12 of 19

I noticed in one of my xml files that worked in the past the ThreadForm is the first setting, don't know if the order matters. If it wasn't such a PITA to load custom thread files I'd try one of the files I know worked before, just don't have time to dig through all the directories and find where they're stored!

HughesTooling_0-1625834935328.png

 

Mark Hughes
Owner, Hughes Tooling
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Message 13 of 19

As we know the built in XMLs seem to work a bit different I'm wonder if the problem you have is mixing mm and inches? Units set to mm then using TPI might be a problem

HughesTooling_0-1625835297804.png

 

Mark Hughes
Owner, Hughes Tooling
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Message 14 of 19
markusthur
in reply to: HughesTooling


@HughesTooling  schrieb:

I noticed in one of my xml files that worked in the past the ThreadForm is the first setting, don't know if the order matters. If it wasn't such a PITA to load custom thread files I'd try one of the files I know worked before, just don't have time to dig through all the directories and find where they're stored!

HughesTooling_0-1625834935328.png

 


Thank you, that I will try, Maybe there is even a hint in the official paper, that it has to be that way.

hmm, didn'T change anything also... It just doesn't want to create the WithWorth shape.

Only way i found till now is doing the Trapezoid and then apply the "rounding" manually.. 😞

That hardcoding of the ThreadForm you mentioned is really confusing, as the document definitely mentions that you can set thread form.. Let me check something 🙂

Message 15 of 19
markusthur
in reply to: HughesTooling


@HughesTooling  schrieb:

As we know the built in XMLs seem to work a bit different I'm wonder if the problem you have is mixing mm and inches? Units set to mm then using TPI might be a problem

HughesTooling_0-1625835297804.png

 


mixing Inches and milimeters at that position seems not to cause the issue. The thread gets constructed correctly, but with trapezoid form. I can even "round" the flat surfaces in order to get the desired form.

But as the offial rounding Radius ist 0.137329 x Pitch i do not want to calculate it by hand every time :-).

As well as the official XML files also do that. I will follow your idea to have threadform as first parameter

Message 16 of 19
HughesTooling
in reply to: markusthur

@markusthur  I've created a bug report here. I've made several tests with files that worked in the past and they all fail now!

 

Mark

Mark Hughes
Owner, Hughes Tooling
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Message 17 of 19
24168157
in reply to: HughesTooling

Seems like people on this thread know plenty about .xml

 

I'm trying to create a lefthand 1.29" x 24TPI thread (it's used on bicycle hubs). I've adding everything succesfully and produced a thread, but it's right handed. Can anyone tell me what i need to do to reverse direction?

 

Thanks.

Message 18 of 19
HughesTooling
in reply to: 24168157

You can set the direction on the thread\hole dialog.

HughesTooling_0-1644830245058.png

 

Mark

Mark Hughes
Owner, Hughes Tooling
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Message 19 of 19
user015M86Y
in reply to: markusthur

Hello Markusthur, I download the Gewindetabellen and it is absolutely a great thread document
Do you have the complete document of 468 pages ?
Thank you for the share

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