topic Re: M15x2.5 thread not listed in Fusion Design, Validate & Document Forum

M15x2.5 thread not listed

kris.chlapek — Tue, 15 Apr 2025 17:02:07 GMT

Hi All

Is there an easy way to add m15x2.5 thread? the biggest coarse is x1.5 unfortunetly

Thanks

Re: M15x2.5 thread not listed

MRWakefield — Tue, 15 Apr 2025 18:17:38 GMT

That's correct, M15x2.5 isn't included in the ISO or ANSI standards so consequently isn't present in the Fusion thread files. I've added M15x2.5 in 6g, 6H, and 4g6g classes to a non-standard ISO metric thread file that's in the zip file attached to a forum post here.

If you have any problems or require any more help just shout.

Re: M15x2.5 thread not listed

kris.chlapek — Wed, 16 Apr 2025 05:44:03 GMT

Thank you very mych.

Re: M15x2.5 thread not listed

kris.chlapek — Wed, 16 Apr 2025 07:52:52 GMT

There seems to be problem with this thread. (sorry not an expert).

Even when i offset the faces by -0.3 to enlarge it, it`s still to small to engage. it`s almost like when it`s modeled the bore size decreases fair amount.

Any thoughts?

Re: M15x2.5 thread not listed

MRWakefield — Wed, 16 Apr 2025 08:59:34 GMT

There shouldn't be anything wrong with the thread. Here's how it looks as-is:

and here it is with a 0.3mm offset on the internal thread:

It's important to perform the offsetting properly. I've added a link in my signature below to a guide I created on this subject.

If you can export your f3d file and post it here I can take a look at it.

Re: M15x2.5 thread not listed

kris.chlapek — Wed, 16 Apr 2025 09:17:08 GMT

Ok, i think i know where the problem is.

I measure the current thread, and the top of the thread (major) is 14.85mm but the minor is 13.58m, so with the defualt this will need 13.5mm drill and change to the MinorDia to 13.55. Do i got it correctly you think?

<Gender>internal</Gender>
<Class>6H</Class>
<MajorDia>15.292</MajorDia>
<PitchDia>13.488</PitchDia>
<MinorDia>13.55</MinorDia>
<TapDrill>13.5</TapDrill>

Re: M15x2.5 thread not listed

MRWakefield — Wed, 16 Apr 2025 09:31:35 GMT

It really depends on which part of the thread is interfering. Generally, if you're 3D printing you want to shift the entire profile to compensate for the inaccuracies of the 3D printing process, not just the minor diameter. Can you clarify whether you're offsetting the faces of the thread in the model or are you only editing the xml file? The more information you can give the easier it will be to determine where it's going wrong for you. Screenshots, photos and/or your model will help a lot. Did you take a look at the guide I mentioned?

Re: M15x2.5 thread not listed

kris.chlapek — Wed, 16 Apr 2025 09:50:14 GMT

Yes, i have looked at your post and i performed the 3 face offset before.

I have now modified the .xml as per the below:

<Gender>internal</Gender>
<Class>6H</Class>
<MajorDia>15.292</MajorDia>
<PitchDia>13.488</PitchDia>
<MinorDia>13.55</MinorDia>
<TapDrill>13.5</TapDrill>

Yet i`m still a bit out. (the attached does not have offset yet)

Re: M15x2.5 thread not listed

MRWakefield — Wed, 16 Apr 2025 10:37:17 GMT

Ok, thanks for the photos and the model. Here are a few observations:

When measuring the minor dia of the external thread with the calipers, are you getting right down into the root? If not then it will obviously show as being larger than it really is.
The general rule of thumb for a metric thread is that you subtract the pitch from the nominal (major) to arrive at the tapping drill size (i.e. the approximate minor dia). In this case 15-2.5 = 12.5. Are you sure this is a metric (i.e. 60°) 2.5mm pitch thread? Your 13.5mm measurement would suggest it's 1.5mm.
The partial xml that you've posted only has the minor diameter increased. Normal practice would be that you need to add the same amount to all three diameter values (the tapping drill value seems to be completely ignored by Fusion btw).
I didn't notice this earlier but the minor diameter in your edited xml is larger than the pitch diameter - In my experimentations I've found that Fusion doesn't like this and I'm not sure what it does to the thread thread profile in these cases.
A side-on view of the part might help determine what this thread is.

Re: M15x2.5 thread not listed

kris.chlapek — Wed, 16 Apr 2025 10:35:14 GMT

This is the problem that i have no idea what thread it is. Looks like it does not conform to anything i know.

It`s definetly 2.5mm pitch to pitch and 13.55 at the root.

Re: M15x2.5 thread not listed

MRWakefield — Wed, 16 Apr 2025 10:54:42 GMT

Thanks for the photo. Yes, from what I can see that doesn't look like a standard metric thread. My advice would be to leave the thread xml as I posted then start with offsetting the minor diameter of your nut such that it's larger than your measured external minor. This will remove any possibility that it's the minors that are interfering. As mentioned, Fusion doesn't like a minor dia larger than the pitch dia, hence the advice to do this with an offset in the model. If it still doesn't fit then start offsetting one of the flanks until it fits. You might need to offset the major as well, it depends how inaccurate the print is. From what I can see in your last photo this is the kind of result you're looking for (this has an offset of -0.6mm on the minor face only):

I hope this helps.

Re: M15x2.5 thread not listed

kris.chlapek — Wed, 16 Apr 2025 10:56:58 GMT

Hard to picture but i tried imperial thread gauge so pitch looks to be 10tpi but obviously is not deep enought to match and measure 0.584od

Re: M15x2.5 thread not listed

kris.chlapek — Wed, 16 Apr 2025 12:08:22 GMT

Finally, i used these values and the -0.2 offset on all 4 faces.

If i did the -0.2 offset, on all 4 faces, then what would the values should be in the end so that i can model without offset?

Thanks

Re: M15x2.5 thread not listed

MRWakefield — Wed, 16 Apr 2025 12:31:19 GMT

The best way I can think of to get the resultant sizes is to:

Create a new sketch on a plane that cuts through the part along its centreline.
Project the intersection of the body with the sketch plane.
Add dimensions or use the measure tool to measure the major and minor dias. You'll need to add extra geometry to measure the pitch dia.

If you're unsure about how to do this then if you can post your current file I'll take a look.

Re: M15x2.5 thread not listed

kris.chlapek — Wed, 16 Apr 2025 12:33:37 GMT

thanks, I appreciate the effort.

File attached

Re: M15x2.5 thread not listed

MRWakefield — Wed, 16 Apr 2025 13:02:51 GMT

No problem, you're welcome.

I've noticed something that will prevent your part screwing on, here's a screenshot with the problem areas highlighted:

These figures seem way oversized for the part you've measured. If you've been printing this as per the model posted then this might be the reason that they're so far away from your measured values. The areas highlighted are due to the chamfers being added before the thread feature. There are a couple of workarounds though. One is to create the thread as cosmetic only, apply the chamfer, then edit the thread and set it to 'modeled'. Another way is to perform a revolved cut. I would correct the highlighted issue and rerun your tests.

Re: M15x2.5 thread not listed

MRWakefield — Wed, 16 Apr 2025 14:07:07 GMT

~~I've just realised that when I open your model it will be using my thread file so the figures in the screenshot in my previous post will not be valid.~~

Ok, scrub that. Because I hadn't edited the thread feature I believe it was using cached geometry.

Re: M15x2.5 thread not listed

kris.chlapek — Wed, 16 Apr 2025 13:57:47 GMT

Removed the chamfer and the -0.2 and it`s good but a bit tight to my liking, so i`m thinkint that this could be 55 degre thread. Cheers

Re: M15x2.5 thread not listed

MRWakefield — Wed, 16 Apr 2025 14:09:39 GMT

It could be, although that's rare these days (except for British and metric pipe threads). You might try printing a half-section that you can lay your original part into to see where it's interfering.