Problem drawing accurate threads

[tjallen29]

Hello everyone,


I'm hoping I can find some help in getting threads to display correctly in WF 2.0 without the model failing.


I'm looking to make 2 1/2-8 UNC threads in a hole that's .817" in length. I should end up with roughly 6.5 threads, with a pitch of .125, right?


Here's my sweep profile:

..and my thread sectionprofile...

...and when I finish the sweep, the feature fails. Entering a pitch of .017 seems to work, but I can't get much smaller than that.

So I'm left being unable to correctly display the thread (4-5 threads instead of 6.5)

Has anyone else encountered this problem and found a way to get around it so that I can use the thread pitch that I want? Am I missing something? This is a common thread right out of the Machinist's Handbook, so I would think that I have all of my values correct and Pro-E should allow me to model it.


Thanks for any help!

 

[FireWild]

Have you tried to modify the accuracy of the part? Change the accuracy to absolute with a value of .0005 or .0002. I suspect the reason the feature fails is because there is a small surface created that's smaller than the relative accuracy will allow.

 

[tjallen29]

Thanks for the reply.


Unfortunately that did not help. I even tried an accuracy of .0001 and the sweep still fails.

 

[tjallen29]

I got it. I looked at my math again and if was a bit off.


Thanks again!

 

[sip]

What is the length of the top of your triangular thread section? If it is the same as or greater than the pitch thesweep becomes self-intersecting, and fails.


Sip

 

[KENLUDE97]

Sip interesting, thanks for the tip.

 

[jimshaw]

What is the length of the top of your triangular thread section? If it is the same as or greater than the pitch thesweep becomes self-intersecting, and fails.


Sip

Thie is a fantastic tip sip! This also holds true for sweeps and swept blends, and is not that intuitive sometimes...