Alab, LLC

Fitting Specifications for 12" x 12" diffusers

3/4" npt (national pipe thread) is a United States Standard, Taper Fit Thread.

Pipe Outside Diameter is 1.050" x 14 threads per inch

(excerpt from ANSI B1.20.1 Thread Specifications)
Nominal
Size
(in.) 
Wrench
Makeup
Length for
Internal
Thread
L3 (in.) 
Total
Length:
End of Pipe
to Vanish
Point
L4 (in.) 
Pitch
Diameter at
Beginning
of External
Thread
E0 (in.) 
Pitch
Diameter at
Beginning
of Internal
Thread
E1 (in.)  
Height of
Thread
(Max.)
H (in.) 
3/4"  .2143"  .7935"  .96768"  .98887"  .05714" 


American Standard Taper Pipe Thread, NPT
Nominal
Size
(in.) 
Outside
Diameter
D
in.
Number
of Threads
Per Inch
n
Pitch of
Thread
P
in.
Normal
Engagement
By Hand
L1
in.
Length of
Effective
Thread
L2
in.
3/4"  1.050"  14 .07143" .339" .5457"