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NPT pipe threads

NPT pipe threads

Please add NPT pipe threads to the thread options in the thread dialog box. Tnx!

293 Comments
WillL84
Collaborator

@SGallowayGMNSX It's sad that people can do this on their own in an afternoon using widely available specifications but the F360 team can't do it in 4+ years

SGallowayGMNSX
Participant
Yes, it is sad. They are more concerned with getting new features and selling bells and whistles. Seems like more updated have been focused on workflow and design enhancements, rather than fixing the basics.
yoshimitsuspeed
Advisor

I think the best solution is finding some modeled threads that fit the standards you are designing around. I have been looking and would love it if anyone knew of any. I have often used models from mcmaster, grabcad and other places but there is no way of knowing how accurate they are. For example a couple weeks ago I cut threads from a Mcmaster part and thankfully I noticed in the model that the threads were left hand threads before printing the part. That shows just how far off they can be but there is really know way of knowing how accurate the threads were modeled and if you are trying to actually use the threads for something could lead to issues with not fitting, not sealing, etc. If AD could at least provide some standardized plugs that we could use joints to cut threads it would be a huge step forward. Of course like I have been saying for years they could take that one step further and have a thread cutting system easily in place that worked on the same principals. Of course they need to make it 1000 times more complicated than it should ever need to be. 
Select face, point, or cylinder, Assign NPT thread, have a nominal depth with a way to adjust depth. Moronically easy. But nope. 

colinNJB25
Advocate

I spent much of the morning playing with this and I can make threads. I will share my solution when finished. In my case, I need to make real threads, like 80% and not points making this harder. The resulting .stl will be the specification for a $30k mold and has to be perfect on the first try or we spend another $30k to fix it. That would be the end of not only my job but also my position. 

doreen_holley
Enthusiast
@colinNJB25 please share your solution w/Autodesk if works and implemented
you are a hero
colinNJB25
Advocate
michaelthompson83
Enthusiast

This is a big problem with this software at the moment due to needing to create a true conical tool path for an NPT thread. We can some times get away with using a normal threading cycle but in this case the customer has supplied 3 different types of gauges to check the thread. One of them being a true conical gauge which has no threads to check the minor cone form. So in this instance i need to use a tool path that radially spirals out as it spirals up.

Hopefully this function will be added soon!

NPT threads are extremely common in oil & gas and subsea work. This will be hugely beneficial to a lot of users who at the moment are probably using an alternative software package due to some of fusions limitations. I machine a lot of internal 1/4, 3/8 amd also 1/2 inch NPT threads on a mill using a solid carbide hob.

CGPM
Collaborator

If your needs are to just threadmill NPT threads in-house then I model a cone to use as a cut tool to create the tapered hole.  After that just select the sides of the hole to threadmill, pick a thread lead, the tool offset, lead in and out that works, raise the tool .005" above the bottom of the pocket and done.  I have done this many times with 1/16"-1/2" NPT threads with a single point threadmill with no issues.  The programmed path is perfect, just how I would hand code it without cam software in 180 degree arcs.  The workaround is pretty simple and fool proof, as long as it is all in-house.

doreen_holley
Enthusiast
What if you 3D print?
##- Please type your reply above this line-##
CGPM
Collaborator

Can you 3d print accurately enough that an NPT thread works?

Anonymous
Not applicable

I often use the 3-D printer to prototype fittings with NPT threads. Even PLA will hold 30 PSI if you have everything dialed in. 

WillL84
Collaborator

@Anonymous I'd never pressurize 3D printed plastic parts (except maybe some parts with the MarkForged with the carbon fiber reinforcement), that's just asking to get a face full of shrapnel. If anything I'd print with 100% infill and/or several walls and just tap with a regular NPT tap.

 

Not saying it's not BS that Fusion still doesn't have NPT threads, it completely is. I use Inventor and only use Fusion for CAM so while I can't put in modeled NPT at least I can put NPT in and have the angles and everything perfect

doreen_holley
Enthusiast
@WillL84 3D printed part is additive manufacturing, which can generate
solid parts that can’t be manufactured (subtractive) traditionally.
Www.dxv.com/3D-printed-faucets/
WillL84
Collaborator

@doreen_holley I know, that's why I said plastic printed parts. @Anonymous said PLA will hold up to 30PSI.

doreen_holley
Enthusiast
PLA might hold pressure but WILL degraded with water (probably even
humidity in the air)
Anonymous
Not applicable
This isn't the place to debate prototype materials. It's to discuss the
lacck of any thread generator for tapered threads in fusion360
WillL84
Collaborator

@Anonymous this isn't the place to cry about what people discuss. Pretty sure there's a crybaby forum somewhere for that.

doreen_holley
Enthusiast
@Anonymous agreed on the materials but the point is the process of 3D
printing NEEDS NPT. Machining a part you can specify a thread but if part
is entirely additive NPT is a MUST have in a model.
WillL84
Collaborator

@doreen_holley It's really not though. As long as you can model in the correct dimensions (ID, taper, etc) you can use an NPT tap to make the threads no matter the process.

yoshimitsuspeed
Advisor

3D printing NPT threads without cleanup can work in some situations. It depends on the type of printing. For example SLS can give pretty nice threads in any orientation. Wheras  FDM will tend to make much nicer threads if the hole is on axis with the Z axis. For holes in other orientations it can be harder to get a good strong sealing thread. It can be possible to shrink the thread and then tap it which is easier than tapping just a tapered hole and also gives a better thread surface because the tap is just cutting slightly into the first layer instead of cutting through multiple layers if you were just tapping a cone. The latter can be much more likely to leak or open up channels within the printed area that can leak. 
It is also easier to reliably print bigger NPT sizes which is also convenient because it's pretty cheap and easy to get a 1/2" tap but many people may have a hard time justifying the cost for a 3" tap if they aren't going to be doing this type of work regularly. But with the right settings in many cases it should be possible to get a 3" thread that will seal. 

Of course as sort of mentioned above pressure is an important part. If you are making parts for a hydraulic system or other high pressure system, mission critical system, high volume chamber, etc it could be very dangerous and unwise to use  3D printing. Especially economical or common home methods like FDM. But we have done quite a lot of small items that hold up to 50 PSI. In fact with these types of applications keeping the tapered thread from splitting the part has been more of a concern than the pressure it's exposed to. Especially on holes that aren't axial to the print head as layer separation is a main issue. 

I have been doing a lot of NPT lately and it has been a big PITA. I need to find some plugs that cover all sizes and can be believed to be correct geometry as most NPT threads online seem to be approximations at best. 
Sadly had AD chosen to take a similar route at any point over the last 4 years they probably could have had a working solution in a matter of days that most of us wouldn't complain about. Instead they seem to want to reinvent every wheel in the most excruciating way they possibly can.  

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