TAP TERMINOLOGY
L 4
C m
L 2
L 3
L
L 1
L 5
C f
L 2
L
L 1
A
A - A
A
S
I
B
B - B
B
d 1 Nominal diameter the diameter used for the purpose of general identification. d m Pitch diameter the diameter measured where the width of the thread is equal to half the pitch. d 2 Shank diameter the diameter of the shank, important for the tapping attachment.
d 3 Chamfer diameter the diameter at the leading end of the chamfer. d 4 Neck diameter the diameter of the reduced section between the thread and shank of the tap. d 5 Core diameter the diameter of a circle tangent to the bottom of the flutes.
I Chamfer
the taper on the threads at the front end of the tap made by grinding and relieving the crests of the first few teeth. a Square the square with rounded corners formed by four flats parallel to the tap axis. The square serves to drive the tap .
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