HELP - Modeling pipe threads

Hello,

I am trying to model a 1.5" tapered NPT thread onto a fluorescent lamp
holder we are planning to die-cast. I've pulled all the numbers out
the Machinery's handbook, created (what I think) are appropriate
helixes and swept cuts, but the thread profile just isn't coming out
right.

Does anyone have any examples of true threads in solidworks - tapered
or otherwise? I could really use some help on this one.

Regards,

Iqbal Lotey
Engineering Technologist
ilotey at ojeezpleasenojunkmail at ledalite dot com

 

Iqbal, the SolidWorks model (2001+) that I've sent to your email
addresses has tapered helixes defining the Path of three Cut-Sweeps.
These Cut-Sweeps create some geometry that is like the thread you want
to create, but it is not geometrically accurate. I only modeled an
approximation of a pipe thread, but at least you can see how it was
done. Be sure to delete the very last feature in the Feature Tree,
appropriately named "Remove-Me".

Hope that helps,
Mark 'Sporky' Stapleton
Charlotte, North Carolina, USA

 

Mark,

Thanks for the help. Your example was basically what I was trying
to do – turns out I had the taper wrong and that's why my threads
looked funny. I was still having problems with leftover material on
the crests of the thread, so I re-thought my method and did it
backwards, by rotating the thread profile around the helix instead of
rotating the "cutter". I can email the file if anyone wants to see.

Thanks again,
Iqbal.

 

Doing it that way makes the root radius uncontrollable. Athough, it
may be fine for your application. My company makes screws, I have to
model threads all the time.

I haven't posted on here in some time, if you wish to contact me,
email me. I remember Spork - at least enough to remember he's very
tallented. From what you've both described, his way is the way I
would model them. True, your radius on your major diameter may not
look good (Solidworks fault), but if you are rolling your threads,
they are not going to be that perfect anyway (unless you're packing
the hell out of the dies)

I always draw the major diameter w/ the taper coming up from the point
to the thread and it's runout to the blank diameter. Then I cut my
threads from the intersection of the runout to the blank diameter.
The one going to the point I obviously cut straight. The one leading
to the blank I taper up to give it a realistic effect. Although I
described the method for modeling a non-tapered machine screw, I would
do the same only add the taper for the pipe thread. For wood or sheet
metal screws (spaced threads) I revolve the thread form as you
described.

I also utilize design tables so I don't have to keep redoing all these
steps.

Let me know if you need models of tooling for roll forming or cold
forming tools and dies. I have a lot for Formax, Naka, etc