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Thread: Programming NPT Thread
10-24-2007, 12:14 PM #1
There are a lot of people here with a lot of knowledge, so I was hoping to get some help on this one.
I need to program an internal 3/8-18 NPT thread single point. I'm using a Fanuc OT control (two G76 lines). I have the machinist handbook, but I don't know where the numbers for the thread comes from.
I need to know the Dia. at the beginning (large ID) and the end of the thread (small ID), the length of thread, and the height of the thread. Where in the tables can I find these values?
Any and all help is much appreciated.
10-24-2007, 02:51 PM #2
Copy/Paste from one of my progs.
Note - better check that feedrate. I think that the Brit thread is 19 instead of 18. ??? Also - you will need to change the 29* to 30* infeed.
Aw heck - here is the other side of the part that has a US thread on it - just the Z's are off...
Think Snow Eh!
10-24-2007, 07:02 PM #3
Hi Ox - Thanks a lot for your reply. When I make standard threads (UNC, UNF, ect), the major, minor, pitch diamters, and heights are clearly shown in the machinist handbook.
Maybe I'm just clueless when it comes to NPT threads, but I'm not sure how you calculated your values.
In that example, you entered 0.6 for your major diameter (since its a 3/8-18 NPT internal thread), is 0.6 the "Wrench Makeup Diameter"?
Also, where did you find the right length of the NPT thread, did you just eye-ball what it should be?
How did you calculate the height of the thread (you put P:0335), but in the handbook, the height says 0.0444?
Your help is really appreciated. Thanks.
10-24-2007, 07:30 PM #4
Mine example was for external. Internal would have the opposite R value.
I didn't git it outta no book. I just had to play with it to git where I wanted it.
.044"? You sure you aint lookin' at the 1/2-14 line? My book shows a standard 18 pitch thread to have a single depth of .035". I may be off on that - but the only diff that will make is on the initial pass depth of cut more or less.
I turn my blank to fit the "Dryseal Profile" guage first and then the thread to fit the other two guages. Here is the turn code that I run:
Again - keep in mind that these Z values are on the sub. You can edit I am sure.
My X values could be off a smidge since there really aint nothin' on these parts to adjust to for sure, I would have just dialed it in on my profile guage. ???
These values were dialed in with "Dryseal" guaging, so the taper should be dead nutz. Now if you change the Z stroke at all you will have to proportionately (WOW! Did I actually spell that? That sucker is LOOONG!) Anyway - you would have to doctor the R value too.
This will run the thread well past the L2 point.
Hope you got all that. ???
Think Snow Eh!
10-24-2007, 07:33 PM #5
Sorry, wusn't thinkin'.
You obviously didn't need my turn code as you must be lookin' fer internal code. [img]redface.gif[/img] :rolleyes:
Think Snow Eh!
10-24-2007, 09:08 PM #6
Check your private messages