i liked post #5 and post #23… but it bears reading the whole 2 page thread, and the different approaches everyone uses…
theres more than one way to skin a cat, LMAO… and to note theres similarities in a lot of them as well.
I'm not all that concerned about the infeed depth, it's easy enough to see the crest width on the external thread while cutting and in my limited experience so far a wider crest/less-than-full-profile thread feels much better, in aluminum. And the internal thread is cut using the external thread as a gage. Wherever the dial is when it fits is just where it is. I should be able to adjust the starting OD/ID dimensions to end up with relatively equal thread depth on both parts.
That's not the way to do it in a production shop but for one-off homemade prototype hacker stuff I'm not going to lose any sleep over it. Hoop is doing parts that have to fit lights he's never seen in person and that's an altogether different beast.
I do keep records of all the dimensions and settings I used for each of my parts so in theory I could recreate them later. How that would work out in reality though...?
Very interesting. #17 is good too. I know the approach in #23 won't always be possible because of sheer lack of extra material available on a given part/design. For instance, on a part that's already cut to final length. On an ID where you have an o-ring land before the thread starts it'd be fine.
That’s a decent “thread” there sedstar, I hadn’t seen any of that stuff before. My numbers are based on some of the constants in Machinery’s Handbook, but it’s good to see that they correspond to some of the methods in that thread. They also correspond to the numbers that the Excel spreadsheet calculator for threading spits out, so I know now that that calculator is accurate: ASME_2A_2B-Inch_Thread_CalculatorVersion2.xlsx You can use this to get the min/max tolerances without doing all of the longhand math that my original (deleted) post was detailing.
Here is a very inexpensive internal threading bit from little machine shop.
I have this setup: http://www.ebay.com/itm/291641042884 $32 delivered, no grinding. And the holder also fits normal TCMT inserts for use as a boring bar.
Quick dummy question about that spreadsheet: It looks like there's no way to directly input a desired pitch diameter. So you have to fiddle with the Major Diameter box at the top until the pitch diameter comes out right?
Pitch diameter is a locked parameter in the spreadsheet, but like I said: Add .65 times the pitch to the pitch diameter and we’ve got the basic OD of the external thread: .65*.05+.875= .9075” (.875 being the desired pitch diameter in this example, .05 being the pitch of a 20TPI thread)