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Inner Threads with ThreadCreator problem
klaus_krämer
Member Posts: 45 ✭✭
I just made a 25 mm wide cylinder of 56mm height with 8.5 mm deep holes on each end (diameter 8.4mm). Quite a simple part:
The 8.4 mm diameter holes on top and bottom shall be threaded with a M8 thread - I started with the upper one:
And now the trouble begins: After threading the top hole, the lower hole has been shrunk to a diameter of 7.15 mm!
WHY the heck??? I detected this only after printing the part with both threads and the screw not fitting into the lower thread!
This seems a bug, because I defined a thread length of 8.5 mm. So why would it affect the whole part?
Another logical inconsistency of ThreadCreator is, that it adds the inner thread to the surface, instead of tapering it into the surface. So every hole with an inner thread has to be drawn with a bigger diameter, e.g. 8.4 mm for a 8 mm inner thread,
I think carving it out would be the better and more logical solution.
Comments
I'm guessing thread creator looks for the end of the part and somehow includes the hole at the other end but that seems a bit odd…
I believe @dave_cowden is the author and might know what's going on…
You could try using threadlabs instead, they are similar tools but with different strengths and weaknesses.
https://cad.onshape.com/documents/5c0528b62c1fbb13a2a0e739/v/f86229e7f586f8517a2068a9/e/7cbb452d4d5e963a034ce616
hi @klaus_krämer
Im sorry you're having this issue. It's clearly a bug!
inner and outer threads are created using various geometry— I think the lower hole getting smaller is some kind of bug in which the area added for the threads is extending too far down.
You're right that cutting into a surface would be more logical— simply because most of the time people will use cad tools to create a tap drill. The current design was motivated by performance considerations— in testing at the time it was a lot slower to cut from the parent part, because the parent part can be arbitrarily complex— whereas dealing with only the threads themselves is quite limited in feature complexity. I can consider changing or at least providing the way you propose whenever i make a new version.
Thanks for posting your experience: whenever i get around to making a new version, i'm planning to consult all of the feedback ive received!
Dave
Thank you, @dave_cowden !
I appreciate a lot, that you even consider providing the way I proposed! Really didn't expect that, as there sure lurks a lot of work behind doing so.
Klaus