Part design - Hole thread profiles. - Custom or pipe threads.

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MeSat
Posts: 38
Joined: Fri Jul 10, 2015 4:43 am

Part design - Hole thread profiles. - Custom or pipe threads.

Post by MeSat »

Is it possible to add more threads to the "Hole" on a local or better yet to FreeCAD in general?

I am thinking of pipe threads and other custom threads for fittings that do not fit into the ones presently provided. I am working on a couple of projects and it will require threads to be modelled for 3D printing or machining. NPT and BSP threads for starters.

Looking into this, I see that there are many different thread standards. It would be nice to have these in the future or the ability to add them as required.

The ability to add custom ones would be nice for 3D printing projects without having to redraw it every time.

Types of Pipe Threads: NPT, BSP, Metric, and Unified Threads (PDF)

https://whatispiping.com/pipe-threads/
chrisb
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Re: Part design - Hole thread profiles. - Custom or pipe threads.

Post by chrisb »

I would like to see this similar to how toolbits are used in Path workbench. These are controlled by files, where some of them are provided by the FreeCAD distribution and additional ones can be added in user space, so that they survive the FreeCAD updates. I'm not sure though if this should go as far as allowing conic threads, because that could make the creation of new threads unnecessary complicated, and may also need refactoring of the basic thread code.
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Silent_Phoenix
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Joined: Sun Sep 04, 2022 9:07 pm

Re: Part design - Hole thread profiles. - Custom or pipe threads.

Post by Silent_Phoenix »

chrisb wrote: Mon Jan 29, 2024 9:07 am
+1
Workshop_Notes
Posts: 543
Joined: Wed Sep 29, 2021 8:35 am

Re: Part design - Hole thread profiles. - Custom or pipe threads.

Post by Workshop_Notes »

MeSat wrote: Mon Jan 29, 2024 4:28 am Types of Pipe Threads: NPT, BSP
NPT threads should be available here:

viewtopic.php?t=67071
viewtopic.php?t=69355

Whitworth form threads of any series (i.e. including BSP) are not currently supported in FreeCAD.
MeSat
Posts: 38
Joined: Fri Jul 10, 2015 4:43 am

Re: Part design - Hole thread profiles. - Custom or pipe threads.

Post by MeSat »

Workshop_Notes wrote: Mon Jan 29, 2024 5:04 pm
MeSat wrote: Mon Jan 29, 2024 4:28 am Types of Pipe Threads: NPT, BSP
NPT threads should be available here:

viewtopic.php?t=67071
viewtopic.php?t=69355

Whitworth form threads of any series (i.e. including BSP) are not currently supported in FreeCAD.
The macro is a good start. Thanks for the pointer. Maybe it can be modified to meet my requirements to support BSP threads. It isn't that complicated.

Have not seen Whitworth for a few decades.
Workshop_Notes
Posts: 543
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Re: Part design - Hole thread profiles. - Custom or pipe threads.

Post by Workshop_Notes »

MeSat wrote: Mon Jan 29, 2024 5:49 pm Have not seen Whitworth for a few decades.
USA and Canada are the main users of NPT threads. If you have seen a threaded pipe in almost any other part of the world, you have seen a Whitworth thread. BSP is Whitworth form. ISO pipe threads are identical to BSP just with the numbers converted to metric.

It would be possible to do a halfway house: use the macro's custom thread with the NPT button and put in dimensions (diameter and pitch) to suit a BSP thread. The result would not be technically correct as it would have a 60 degree thread form with flat roots and crests (BSP is 55 degrees with rounded roots and crests) but might work for 3D printing. If you are printing a male thread, a steel female pipe fitting could be used to massage away the worst of the discrepancies.

The other difficulty is that tables of NPT threads have the major diameter defined as the pipe outside diameter. Hence, for a standard NPT thread, the major diameter you enter into the macro reduces at a 1:16 taper as you move up the thread.

With BSP thread tables, the major diameter given in the tables is at the gauge length of the thread. It would not be correct to use this number in the macro (the result would be too small). You would have to calculate the NPT major-diameter-equivalent number for each BSP thread.
MeSat
Posts: 38
Joined: Fri Jul 10, 2015 4:43 am

Re: Part design - Hole thread profiles. - Custom or pipe threads.

Post by MeSat »

USA and Canada are the main users of NPT threads. If you have seen a threaded pipe in almost any other part of the world, you have seen a Whitworth thread. BSP is Whitworth form. ISO pipe threads are identical to BSP just with the numbers converted to metric.
I will take your word for this. Will have to look into it more.

With products coming into Canada from around the world, it is an issue. I purchased some new pressure gauges at a local store and all the connections, other than the inlet and outlet are BSP. I have to order BSP fittings for my projects, or a large number of adapters.

I have just received a couple of packages of pneumatic fittings and they are all "metric" threads which I have to make drawings for.

So, from an international view, meeting the requirements for all users is not a bad incentive.
With BSP thread tables, the major diameter given in the tables is at the gauge length of the thread. It would not be correct to use this number in the macro (the result would be too small). You would have to calculate the NPT major-diameter-equivalent number for each BSP thread.
May take some work but it could be done and I think it would be worth it for a future upgrade.
grumpy_pirate
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Joined: Wed Feb 07, 2024 9:37 am

Re: Part design - Hole thread profiles. - Custom or pipe threads.

Post by grumpy_pirate »

What would greatly help is if Sketcher had an option to generate various profiles from a database or using formula. Like a cutting profile for BSP 1/2 inch, etc. I model a lot of external threads and designing a cutter is always a pain (mostly to learn and get dimensions from various standards).
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