logo

Common types of pipe threads used in the piping industry

  Thread Information
  Threads of many different kinds are used for different purposes in piping components.
The following are the more common types of pipe threads used in the piping industry :

1. NPT Tapered Pipe Threads

NPT (National Pipe Tapered) is made to specifications outlined in ANSI B1.2.

2. NPTF (National Pipe Thread Dryseal) (made to specifications outlined in ANSI B1.20.3.) This piping end is also used on hydraulic and pneumatic equipment.

3. ISO 7/1 Tapered Pipe Threads

International Organization For Standards (ISO 7/1) Tapered (PT)
.   ISO tapered threads are equivalent to DIN 2999. BSP Tr, JIS B0203, R 1/8 and R 1/4 Keg. etc. In application ISO threads are used similar to NPT threads. However, care should be used that ISO and NPT threads are not mixed. ISO threads have a 55 deg angle versus 60 deg  for NPT. The root and crest configurations are different from NPT. Thread pitch is usually measured in millimeters but may be expressed in Inch. In most sizes the threads-per-inch are different.

4. ISO 228/1 Parallel Pipe Threads

(International Organization For Standards (ISO 228/1) Parallel (PF))
ISO Parallel threads are equivalent to DIN ISO 228/1, BSP PL, JIS B0202, G 1/8 and G 1/4 etc.

These pipe threads are similar in configuration to ISO 7/1 threads except there is no taper. Therefore do not work by thread interference like the tapered pipe threads of ISO 7/1 or NPT. A gasket, cutting face or O-Ring is normally used to seal the parallel female threaded component.

Comparison Chart

Pipe Threads

Nominal Size

Threads Per inch

Pipe O.D

Included Thread
Angle

Pitch

1/16"

NPT/NPTF 27
ISO  28 

.312"
.312" 

60 deg
55 deg  

.037"
.036"

1/8"

NPT/NPTF 27
ISO  28 

.405"
.402" 

60 deg
55 deg

.037"
.036"

1/4"

NPT/NPTF 18
ISO  19 

.540"
.532" 

60 deg
55 deg

.0556"
.053" 

3/8"

NPT/NPTF 18
ISO  19 

.675"
.677 

60 deg
55 deg

.0556"
.053" 

1/2"

NPT/NPTF 14
ISO  14 

.840"
.838" 

60 deg
55 deg

.0714"
.071" 

3/4"

NPT/NPTF 14
ISO  14 

1.050"
1.060" 

60 deg
55 deg

.0714"
.071" 

1"

NPT/NPTF 11 1/2
ISO  11 

1.315"
1.327" 

60 deg
55 deg

.087"
.091" 

1 - 1/4"

NPT/NPTF 11 1/2
ISO  11 

1.660"
1.669" 

60 deg
55 deg

.087"
.091"

1 - 1/2"

NPT/NPTF 11 1/2
ISO  11 

1.900"
1.902" 

60 deg
55 deg

.087"
.091"

2"

NPT/NPTF 11 1/2
ISO  11 

2.375"
2.374" 

60 deg
55 deg

.087"
.091"

basic table data from: Imex/edited by Maryland Metrics


THINK ! - MARYLAND METRICS - The One-Stop Source For Metric & British Sized Fasteners, Wrenches, Cutting, & Measuring Tools, Metal Shapes, Oil Seals, O-Rings, Mechanical Power Transmission Equipment, Bearings, Hydraulic and Pneumatic Fittings & Tubing, Workholding Components, Plumbing Fittings, & Some Electrical & Electronic Components.

Click: http://mdmetric.com   for the MARYLAND METRICS   P.O. Box 261   Owings Mills, MD 21117 USA website.

Phones: (800) 638-1830 or (410) 358-3130 are available Monday-Friday 8:30 AM to 5:30 PM Eastern time.
Faxes: (800) 872-9329 or (410) 358-3142 & E-mail are available anytime.
Warehouse & showroom hours are Monday-Friday 10 AM to 5:30 PM.
[ To: Maryland Metrics home page ] [ To: Maryland Metrics Product Guide ] [ e-mail to Maryland Metrics ]
Please note that all Trademarks and Tradenames are the property of their respective owners.
copyright 1999, 2001, 2004, 2015 maryland metrics -- all rights reserved -- ver ll27b thdform3.htm