Hi fellas,
As a retired engineer and gunsmith I beg to differ on the format of taps and dies to buy. I hate metric anything! be it taps and dies or klms or liters and everything else! The BA thread system is different to all the other thread forms and is extrmely usefull. The size variation is superb. I am building a 5 inch gauge steam loco called "Simplex" and I found BA threads were excellent to use. Another thread form that I use even more than BA threads is the American Number series, these run from 1 thru to 12. These come in both a fine and a coarse thread. Both the coarse and fine have their most excellent points in use. I used a lot of the Fine series when I had my Gunsmithing business and they were very successful as a thread form. The problem with metric threads (Ugh! SIC!) is the lack of sizes. ie, the variation is too great between sizes. If you are going to use a fine thread for a project and cant decide between BA and the Number Series (US), then compare the thread form of the BA to the US and metric forms. BA threads have a thread angle of 47.5 degrees and the metric (choke) and all US threads have a thread angle of 60 degrees. There is another thread form used in special machinery called Acme but this is never used in small projects.
The small diameter US threads that are given a number can be a problem trying to figure out what the number means relative to the diameter of the screw. There is an easy way to figure this out :-
Take the Number of the screw , eg, '10' and multiply this number by 13.
10 x 13 = 130
to the resulting number, add 60
130 + 60 = 190
190 is the Major Diameter of the screw in "Thou's"
= 0.190" Diameter.
I hope this helps you all a little more to understand threads. If you have any problem about threads and screwcutting, feel free to have a chat with with me.
Joe
I hope this helps you
