Cutting threads in brass or SS.

[Jerry.S]

New guy here, looking for information on how to cut, .075-16UNF-2A threads on a 7x12 desk top lathe.

I do know what type of threads it is; I just don’t how to cut them so that the tolerance meets the 2A standard.

It is for High pressure breathing air. It will be for a small cascade system that will be pressurized to a max of 2300 psig. @ 18 cf of volume or greater. (Adding extra bottles).

Thanks

[packrat]

Are you sure you didn't mean .75 x 16UNF threads? 16 threads per inch on a .075 diameter would be REALLY coarse not fine

[Jerry.S]

Are you sure you didn't mean .75 x 16UNF threads? 16 threads per inch on a .075 diameter would be REALLY coarse not fine

yea .750 not .075, duh.

[Jerry.S]

Well did some searching and found the info about the 2A standard:

"The Unified Thread Standard (UTS) defines a standard thread form and series—along with allowances, tolerances, and designations—for screw threads commonly used in the United States and Canada. It has the same 60° profile as the ISO metric screw thread used in the rest of the world, but the characteristic dimensions of each UTS thread (outer diameter and pitch) were chosen as an inch fraction rather than a round millimeter value. The UTS is currently controlled by ASME/ANSI in the United States.

A classification system exists for ease of manufacture and interchangeability of fabricated threaded items. Most (but certainly not all) threaded items are made to a classification standard called the Unified Screw Thread Standard Series. This system is analogous to the fits used with assembled parts.

Classes 1A, 2A, 3A apply to external threads; Classes 1B, 2B, 3B apply to internal threads.

Class 1 threads are loosely fitting threads intended for ease of assembly or use in a dirty environment.

Class 2 threads are the most common. They are designed to maximize strength considering typical machine shop capability and machine practice.

Class 3 threads are used for closer tolerances.

Thread class refers to the acceptable range of pitch diameter for any given thread. The pitch diameter is indicated as Dp in the figure shown above. There are several methods that are used to measure the pitch diameter. The most common method used in production is by way of a Go/no go gauge."

So if anyone else needs the info the full info is here:

http://en.wikipedia.org/wiki/Unified_Thread_Standard