Is there a formula or basic guide line to breaks in each thread on a bottle & cap? (variable helix)
I designed a variable 2.5 rev. helix sweep (extruded on the cap and bottle).
.3 inch pitch on 1st revolution starting from the bottom going up
.09 inch pitch on the remaining rev's.
I used a continuous sweep with no breaks in the threads.
But every bottle & cap I looked at has breaks at certain degrees of each revolution.
Is there a formula or basic guide line to these breaks in each thread?
http://www.threadspecs.com/ has a download section where you can get PDF files with details for various thread sizes used on plastic bottles. The site is currently dead, but I was on it last week and it worked well.
I also found this site that has two of the PDF files available: http://imajeenyus.com/mechanical/20120508_bottle_top_threads/index.shtml
The location and duration of the vents you mentioned are detailed.