[modeleng] Re: BA/ME Thread Query

Bede said:
>Recent searches for thread types turned up a list of BA threads that 
went all the way to 25BA with a tpi count of several hundred <

I read that the BA thread (actually the Swiss Thrury thread) was 
originally for horological work, which was why it went  down to 25BA. 
Tubal Cain says that sizes below 16BA are generally unobtainable, having 
been replaced by horological threads. The 47-1/2 degree pitch angle gave a 
much stronger thread, which was important in these very small sizes where 
the stresses could be proportionally very high. Until 1951, the BA thread 
was a metric thread, but the standard BS57:1951 went to inch units. It is 
the only logical thread system, where the pitch of each size is 0.8 of the 
pitch the size above.

I use a lot of BA still in electronic work, basically because of my 
stocks!

Peter Chadwick
Swindon.

MODEL ENGINEERING DISCUSSION LIST.

To UNSUBSCRIBE from this list, send a blank email to, 
modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.

Other related posts: