Cut Threads

Hello to all,
When I model threads in a shaft without a thread relief at the end
using the Helical Sweep>Cut command I don't want the last thread to
end abruptly but gradually. Like when you're single pointing the
thread and pulling the cutting tool slowly.
Is there a way to do a gradual ending to the thread?
Thank you for your expertise.
Reply to
1-2-3
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After I have successfully cut my helical sweep, I go back in & add a little "tail" to the end of my sweep profile sketch. For external I go away from the center, for internal I go towards the center. I just make them on the fly, quickly, nothing fancy.
This can sometimes fail if you reference a centerline when creating the thread form sketch. What I do is position my threads using a temporary centerline on the P.D. Then I delete the centerline & dimension the form to the sweep profile. Truncating at the Major or minor (internal or external) threads & wham! its pretty damn close to a "real" thread. I make them slightly looser when getting rapid prototypes made & they work well.
We use the cut threads rather than cosmetic for 3 reasons. One is weight (volume) which must be very accurate on small parts that are high volume. Second reason is we make working prototypes from the models. Third is that they look cool as hell in drawings & jpegs from the models. The marketing pukes LOVE the pics. Tapered pipe threads look very cool. ;)
Reply to
Bruin
It's hard (at least for me) to describe so I went ahead & posted some jpegs of what the sweep profile, thead form, & a cut away view of the threads with the run-out.
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Reply to
Bruin
That's got it...
I worked in the pressure industry for a while and we had to have modelled threads on occassion as well. The picture labelled "sweep" is the key. Granted, this one is for an internal tapered pipe thread, but the thought is the same. For a UN thread, do the same thing with the sweep profile, but the initial line will be parallel to the axis. The angle of the little tail at the end will determine how fast the thread tapers out.
Good Luck
Bru>
Reply to
Paul
Another cute violation of OCCAM´s razor.
Things made much more complicated than necessary. For marketing purposes and the joy of playing with 3DCAD.
But that´s the way it goes once computers are powerful enough (an engineer´s manpower and -time seems not to count any more).
Before standardization of threads was invented and nuts´n´bolts became most common some hundred years ago physical threads were cut *manually*, one by one, in a process as difficult as forging a sword.
It seems at least engineering is heading back there.
Reply to
Walther Mathieu
Amen to that!
I'm the poor bastard who has to grind the thread profile in the mould cores. Often, all you get to take the measurements from is a poorly translated solid. Then, when you ask for a simple cut-view of the thread, preferably as a DXF file (all you really need is basically the pitch, the pitch diameter and the bottom diameter) you get a cut view consisting of thousands lines and splines and whatnot, all in the wrong scale, and all in a multitude of hideous colors.
Sometimes I want to cry...
Reply to
Jan Nielsen
Don't cry for me Jan Nielson...
Reply to
takedown
Seems that the SLA machine can't seem to make a thread without them being in the STL. At least the one we use.
Reply to
Bruin

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