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".
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.
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