0-80 thread on a ..450 pitch diameter? 1

[jackk]

I'm designing two thin-walled parts that are to be threaded together. I don't have enough wall thickness for standard thread, so I'd like to use a 0-80 UNF thread profile on a Ø.450 pitch diameter. I've been able to 3D model the external and internal threads, but how do I specify such a thread on the drawings so they can be machined?

 

[CheckerHater]

Special UN threads usually identifies as UNS.
You specify nominal diameter and pitch as usual; if necessary, it's okay to add actual Major, Pitch, and Minor diameters (with tolerances), also root radius, long / short engagement; everything that's "special" about your special thread.

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[drawoh]

jackk,

From a specification point of view, what is the difference between a 0-80UNF thread on a Ø.450" pitch circle, and a 4/-16UNC thread on a Ø10.000" pitch circle? The small thread needs a more accurate positional tolerance.

--
JHG

 

[3DDave]

It's a misunderstanding - he wants 80 TPI with a 0.45 pitch diameter, which isn't how threads are typically spec'ed. Normally it is OD and thread pitch. 0-80 is one of the odd ones with the OD having a symbolic number to indicate 0.060 OD. The thread profile and thread profile tolerance is independent of diameter anyway.

 

[drawoh]

1/2-80 Special Pitch Tap, High Speed Steel???

I did not work out the pitch diameter.

1/4-80UN is used on some optical translation stages. The taps are available.

--
JHG

 

[geesaman.d]

I'm lazy - I'd find the baseline thread spec in Machinery's Handbook and add to each diameter in the table until it's the size I want. Then I'd probably write out each item in that thread spec table that could possibly apply to eliminate any confusion.

I also agree to go looking for off-the-shelf taps. Maybe there is an existing thread spec that gets use for another industry and you can piggyback on its tooling availability.