Fittings & Adapters - Thorburn Flex Inc

North American Thread Types
HOW TO MEASURE THREADS
Use the thread pitch gauge to
determine the number of threads
per inch. Or in the case of metric
connections, the distance between
threads. Place the gauge on the
threads until the threads are snug.
Match the measurements to the
charts. Comparison of gauge and
coupling threads against a lit background
will assure an accurate
reading.
To measure ID/OD: With the Caliper,
measure the thread diameter at the
largest point: OD for male threads
and ID for female threads. Match
measurements to charts.
To measure sealing surface angles:
Female connections are normally
measured by inserting
the gauge into the connection
and placing it on the
sealing surface. If the centreline
and lines of the connection
match, the correct angle
has been determined.
Male flare type connectors
are normally measured by
placing the gauge on the
sealing surface. If the centrelines
of the connection
and gauge are parallel,
the correct angle has
been determined.
ID
OD
Female
Male
North American Thread Types
N = National P = Pipe T = Tapered Thread
F = Fuels S = Straight Thread M = Mechanical Joint
NATIONAL PIPE THREADS
(National Pipe Tapered Threads for Fuels) is a dryseal thread
used for male and female ends.The NPTF male has tapered threads and
30° inverted seat. It mates with the NPTF, NPSF or NPSM female. The
NPTF female has tapered threads and no seat. The seal takes place by
deformation of the threads. The NPSM female has straight threads and a
30° inverted seat. The seal takes place on the 30° seat. Additional sealing
aids, such as teflon tape are often used with these tapes.
The NPTF connector is similar to, but not interchangeable with the BSPT
(British Standard Pipe/Tapered) connector. The thread pitch differs in most
sizes and the thread angle is 60° instead of the 55° angle on BSPT threads
(see British Thread Types page 29-30).
(National Pipe Straight Threads for Mechanical Joint) is
used on female swivel nut or iron pipe swivel adapters. The leak-resistant
joint is made by a tapered 30° convex seat in the coupling end. A
properly chamfered NPTF male will seal with the NPSM female.
(National Pipe Taper Threads) can connect
with a NPTF or NPT female end. It is similar to the
NPTF in all areas except for the following:
1) There is no 30° inverted seat;
2) Thread root and crest is sharp “V”-shaped with
minimum truncation:
3) Tape or sealing compound required for assembly.
THREAD NOMENCLATURE
3