internal threads 3

[kross68]

1)i am seeking technical information concerning 2-56 unc 3B internal threads. specifically the differences between the strength, using a cut tap and using a roll tap.
2)also the dimensional differences between the minor diameters using a cut tap and a roll tap
3)is there a mil-spec that authorizes the use of a roll tap in place of a cut tap

 

[KENAT]

2) A #2(.086)-56 UNC-3B thread has to meet the dimensional limits given in ASME B1.1 regardless of manufacturing method. I'm not sure if one method will tend toward one extreme of the tol range but they will be interchangeable from a fit/form point of view.

This forum can be a little quiet so you may not get the answer you need. forum725 may be a better place, try not to double post though perhaps redflag this post (link below) and ask for it to be moved or something.

KENAT, probably the least qualified checker you'll ever meet...

 

[mrainey]

The pre-tap minor diameter calculates .007 - .009 larger for a roll tap (depending on thread percentage). You generally aren't able to use all the minor tolerance with form tapping, because the geometry at the crest of the formed thread will be influenced by the minor diameter.


Software For Metalworking

http://closetolerancesoftware.com

 

[mrainey]

Here's some useful information.

http://www.ctemag.com/dynamic.articles.php?id=197

Software For Metalworking

http://closetolerancesoftware.com

 

[chicopee]

Machinery handbook may answer several of your questions.
As far as strength determination, a machine design textbook that you would be assigned during your junior or senior year in college, will show you how to calculate that.