Information on Screw Threads
This thread was used for small diameter
threads (below 0.25 inches diameter). The thread has radiused
roots and crests and has a flank angle of 47 degrees and a
half degrees. The thread size varies from BA number 23 (0.33
mm diameter with a pitch of 0.09 mm) to BA number 0 (6mm diameter
with a pitch of 1 mm). Relative to the Whitworth thread the
depth of the BA thread is smaller size for size. The thread
form is now redundant and has been replaced by Unified and
Metric threads.The form of the thread is shown in the diagram:
If
p = pitch of the thread
d = depth of the thread
r = radius at the top and bottom
of the threads
then:
d = 0.6 p
r = 2 p /11
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