General Technical Information

TubeFit Industrial Products provide a wide range of hose & fitting solutions to suit all industries.

Thread Information

What Is A Pipe Thread?

A ‘Pipe Thread’ is a ‘universal’ thread that enables port connection via a common thread form. With the addition of a tube connection fitting, pipe threads can be used to connect tube to the port of a piece of equipment or allow adaptation, both sizing and/or configuration, to satisfy a given situation. However, depending upon the place of manufacture or the industry in which you are working, different ‘universal’ pipe threads may be specified.

In Australia, most specifications will demand either BSP (British Standard Pipe – Taper or Parallel) or NPT/NPS (American Pipe (Taper/Straight). The fundamental difference with these two ‘universal’ threads is the pitch or threads per inch (T.P.I.) and the thread angle.

Pipe thread sizes are determined by the ‘nominal bore’ of pipe and, as such, can be very confusing when ordered. Confusion is often encountered because the wall thickness of the pipe is not included in the calculation for BSPT, BSPP, NPT or NPS thread specifications.

Threads At A Glance

The following tables have been prepared to show information relating to the thread form of both ends of a tube connection fitting – tube end and pipe end.

Nom. Size British Pipe Thread
BSP (G Series)
Threads BSP BSP
T.P.I. Angle O.D. (mm) Min. Dia. (mm) Max. Dia. (mm)
1/8 28 55 9.62 9.51 9.73
1/4 19 55 13.03 12.91 13.16
3/8 19 55 16.54 16.41 16.66
1/2 14 55 20.82 20.67 20.96
3/4 14 55 26.30 26.16 26.44
1″ 11 55 33.07 32.89 33.25
11/4 11 55 41.73 41.55 41.91
11/2 11 55 47.62 47.44 47.80
2″ 11 55 59.44 59.25 59.62
Nom. Size American Pipe Thread
NPS – National Pipe Straight / NPT – National Pipe Taper
Threads NPS NPT
T.P.I. Angle O.D. (mm) Min. Dia. (mm) Max. Dia. (mm)
1/8 27 60 10.29 10.27 10.29
1/4 18 60 13.77 13.69 13.77
3/8 18 60 17.15 17.07 17.15
1/2 14 60 21.34 21.26 21.34
3/4 14 60 26.67 26.59 26.67
1″ 11.5 60 33.40 33.31 33.40
11/4 11.5 60 42.16 42.07 42.16
11/2 11.5 60 48.26 48.17 48.26
2″ 11.5 60 60.33 60.24 60.33
AS IS0 7.1/2 (previously AS 1722.1) Sealing Threads of Whitworth Form (R Series)

Commonly termed BSPT, gas thread, sealing thread, dry seal thread or engineering thread, AS IS0 7.1/2 (previously AS 1722.1) require mating threads, including a combination of parallel and tapered sealing ends, to effect a seal without the aid of any form of thread sealant or gasket. Generally longer and more bulky than the AS1722.2 equivalents, pipe threads manufactured to meet AS IS0 7.1/2 (previously AS 1722.1) have a limited working life if continually disassembled and re-made.

AS1722.2 Fastening Threads of Whitworth Form (G Series)

Commonly termed BSP, MI, FI or plumbing thread, the thread will require a sealing aid to effect a positive seal. The sealing agent may take the form of a gasket, O-Ring, thread tape, hemp or thread paste. Threads manufactured to AS1722.2 are used extensively in the Plumbing Industry. If used in the correct manner, threads manufactured to AS1722.2 can be disassembled and re-made many times over.

Tube Thread Table

A ‘tube thread’ is a generic term used for identifying the thread form, of the tube end, of a tube connection fitting and not a specific thread.

Tube O.D. Standard Compression Internal Compression SAE 45˚ Flare SAE 45˚ Inverted Flare
1/8 5/16 x 24UNF 9/32 x 26BRASS 5/16 x 24UNF 5/16 x 28UNS
3/16 3/8 x 24UNF 3/8 x 24UNF 3/8 x 24UNF 3/8 x 24UNF
1/4 7/16 x 24UNS 7/16 x 24UNS 7/16 x 20UNF 7/16 x 24UNS
5/16 1/2 x 24UNS 1/2 x 24UNS 1/2 x 20UNF 1/2 x 20UNF
3/8 9/16 x 24UNEF 9/16 x 24UNEF 5/8 x 18UNF 5/8 x 18UNF
1/2 11/16 x 20UN 3/4 x 24UNS 3/4 x 16UNF 3/4 x 18UNS
5/8 n/a 7/8 x 20UNEF 7/8 x 14UNF n/a
3/4 n/a 1.025 x 18UNS 11/16 x 14UNF n/a
4mm 5/16 x 24UNF n/a n/a n/a
6mm 7/16 x 24UNS n/a n/a n/a
8mm 1/2 x 24UNS n/a n/a n/a
10mm 9/16 x 24UNEF n/a n/a n/a
12mm 11/16 x 20UN n/a n/a n/a
Thread Abbreviations & Definitions

The thread types listed below are representative of some of the common threads and terms used in general industry.

Thread Abbreviation Definition                                   
ANP American National Pipe
ANPT American National Pipe Taper
Brass Thread Fine thread common to brass machining and always 26TPI regardless of major diameter (Whitworth form)
BSP British Standard Pipe
BSPP British Standard Pipe Parallel
BSPT British Standard Pipe Tapered
Dry Seal A generic term referring to a thread that seals without the aid of a thread sealant or washer
Engineering Thread A term referring to a thread capable of sealing without the aid of a thread sealant or washer
F.I. Female Iron (BSP Female – common in the Plumbing Industry)
GAS A term referring to BSPT or NPT thread (common in Automotive and Plumbing Industry)
J.I.C. Joint Industries Conference or J.I. Case
M.I. Male Iron (BSP Male – common in the Plumbing Industry)
NPS National Pipe Straight (American pipe thread)
NPT National Pipe Taper (American pipe thread)
NPTF National Pipe Taper Fuel (Internal, straight, American pipe thread)
TPI Threads per inch
Pipe Thread A term referring to BSPT/BSPP or NPT/NPS thread
Plumbing Thread A term referring to BSP fastening thread
P.T. Sealing, tapered, pipe thread of Whitworth form
SAE Society of Automotive Engineers
Sealing Thread A term referring to a thread capable of sealing without the aid of a thread sealant or washer
Tube Thread Thread used on the tube end of a tube connection fitting
UN Unified National (not standard UNF)
UNEF Unified National Extra Fine
UNF Unified National Fine (formally SAE)
UNS Unified National Special (not standard UNF)

Maximum Working Pressures

Maximum Working Pressure Tables for Tube Connection Fittings (kPa)

All working pressures are calculated at an ambient temperature using a safety factor of 4:1. Generally, working pressure is dependent upon the type of tubing used and not the fitting. Consequently the tables shown below should be used as a guide only.

Hydraulic Applications Only – Maximum Working Pressure (kPa)
Tube O.D. Stand Compression Internal Compression SAE 45˚ Flare SAE 45˚ Inverted Flare Fleetfit Air Brake Pneufit
1/8 3500 3500 17250 17250 n/r n/r
3/16 3500 3500 17250 17250 n/r n/r
1/4 2750 2750 13750 13750 n/r n/r
5/16 2750 2750 13750 13750 n/r n/r
3/8 2000 2000 10400 10400 n/r n/r
1/2 2000 2000 7000 7000 n/r n/r
5/8 n/a 1400 7000 n/a n/r n/r
3/4 n/a 1400 7000 n/a n/r n/r
4mm 3500 n/a n/a n/a n/r n/r
6mm 2750 n/a n/a n/a n/r n/r
8mm 2750 n/a n/a n/a n/r n/r
10mm 2000 n/a n/a n/a n/r n/r
12mm 2000 n/a n/a n/a n/r n/r

n/a = Not Available

n/r = Not Recommended for Hydraulic Applications

Pneumatic Applications – Maximum Working Pressure (kPa)
Tube O.D. Stand Compression Internal Compression SAE 45˚ Flare SAE 45˚ Inverted Flare Fleetfit Air Brake Pneufit
1/8 2000 2000 4800 4800 1050 1800
3/16 1750 1750 4800 4800 1050 1800
1/4 1400 1400 4800 4800 1050 1800
5/16 1400 1400 4800 4800 1050 1800
3/8 1050 1050 2750 2750 1050 1800
1/2 1050 1050 1750 1750 1050 1800
5/8 n/a 700 1750 n/a 1050 n/a
3/4 n/a 700 1750 n/a 1050 n/a
4mm 2000 n/a n/a n/a 1050 1800
6mm 1400 n/a n/a n/a 1050 1800
8mm 1400 n/a n/a n/a 1050 1800
10mm 1050 n/a n/a n/a 1050 1800
12mm 1050 n/a n/a n/a 1050 1800

n/a = Not Available

Pipe End Pressure Ratings – Maximum Working Pressure (kPa)
Pipe Size Brass Alloy
Hydraulic Pneumatic
1/8 13750 3500
1/4 13750 3500
3/8 13750 2750
1/2 10400 2750
3/4 7000 2000
1 4000 1250
Copper Annealed Seamless ASTM B-75 or Equivalent

Calculated, maximum working pressure (kPa) for temperatures between 6.7° and 37.8°C. Burst pressure of copper tube is 5 times that of the working pressure.

Tube Wall Thickness – Maximum Working Pressure (kPa)
Tubing O.D. 0.71mm ISWG 22 0.91mm ISWG 20 1.22mm ISWG 18 1.63mm ISWG 16 2.03mm ISWG 14
1/8 18700 23700
3/16 11920 15300 22150
1/4 8780 12080 16200 22000
5/16 6870 9380 12600 17300
3/8 5650 7680 10200 14000 18500
1/2 4170 5630 7450 10100 13450
5/8 4440 6090 7980 10400
3/4 3670 4850 6540 8540
1 2720 3700 5070 6260

Corrosion Rating Charts

Alloy Group Definitions
  • Copper
  • 385 Brass Alloy
  • 352 DZR Brass Alloy
Corrosion Rating Charts

The accompanying charts give relative corrosion resistance ratings for copper and the commonly used copper alloys. These ratings are based on consideration of laboratory test data, service experience and a general knowledge of corrosion resistant properties; however, it must be fully recognised that the ratings are relative only and definite unqualified recommendations of corrosion resistance cannot be made.

When interpreting the data, it should be remembered that corrosion resistance or rate of corrosion is greatly affected by conditions of exposure such as presence of oxidising agents, velocity of solution, aeration, temperature and similar factors.

In general, the information in the tables refers to non-oxidising conditions, low velocities (below 1.2 metres per second) and ambient temperatures.

Corrosion Rating         Definition
E (Excellent) The metal should be suitable under most conditions of use.
G (Good) The metal offers good corrosion resistance.
It may be considered in place of a metal with an “E” rating when some property other than corrosion resistance governs its use.
F (Fair) The metal offers fair corrosion resistance.
N (Not to be used) The metal is not suitable.
Corrosion Media     Copper    385 Brass 352 DZR Brass
Acetic Acid G N F
Acetic Anhydride G N F
Acetone E E E
Acetylene N E N
Alcohols E E E
Alum G N G
Alumina G E E
Aluminium Chloride E N F
Aluminium Hydroxide G E E
Aluminium Sulfate E N G
Ammonia, Absolutely dry N E E
Ammonia, moist N N N
Ammonium Hydroxide N N N
Ammonium Chloride N N N
Ammonium Nitrate F N N
Ammonium Sulfate E N N
Amyl Acetate E G E
Amyl Alcohol F E E
Aniline F F F
Aniline Dyes E F F
Asphalt E E E
Atmosphere, Industrial E G E
Atmosphere, Marine E G E
Atmosphere, Rural E E E
Barium Carbonate G E E
Barium Chloride E N F
Barium Hydroxide E G E
Barium Sulfate F E E
Barium Sulfide E G G
Beer E G E
Beet Sugar Syrups E G E
Benzine E E E
Benzoic Acid E G E
Benzol E E E
Black Liquor F N N
Bleaching Powder, Wet G N G
Borax E E E
Bordeaux Mixture E G E
Boric Acid E G E
Brines G N G
Bromine, Dry E E E
Bromine, Moist G N F
Butane E E E
Butyl Alcohol E E E
Butyric Acid G F G
Calcium Bisulfite G N G
Calcium Chloride G N G
Calcium Hydroxide E G E
Calcium Hypochlorite G N G
Cane Sugar Syrups E G E
Carbolic Acid G G G
Calcium Dioxide, Dry E E E
Carbon Dioxide, Moist G F G
Carbonated Water G F G
Carbonated Beverages G F G
Carbon Disulfide G E E
Carbon Tetrachloride, Dry E E E
Carbon Tetrachloride, Moist G N G
Castor Oil E E E
Chlorine, Dry E E E
Chlorine, Moist F N F
Chloracetic Acid G N F
Chloroform, Dry E E E
Chromic Acid N N N
Cider E F E
Citric Acid E F E
Coffee E E E
Copper Chloride F N F
Copper Nitrate F N F
Copper Sulfate G N G
Corn Oil E G E
Cottonseed Oil E G E
Creosote E G E
Crude Oil G F G
Ethers E E E
Ethyl Acetate E G E
Ethyl Alcohol E E E
Ethyl Chloride G F G
Ethylene Glycol E G E
Ferric Chloride N N N
Ferric Sulfate N N N
Ferrous Chloride G N G
Ferrous Sulfate G N G
Formaldehyde E G E
Formic Acid G N F
Freon E E E
Fruit Juices G N F
Fuel Oil E F E
Furfural E G E
Gasoline E E E
Gelatine E E E
Glucose E E E
Corrosion Media     Copper    385 Brass 352 DZR Brass
Glue E G E
Glycerine E E E
Hydrobromic Acid F N F
Hydrocarbons, Pure E E E
Hydrochloric Acid F N F
Hydrocyanic Acid N N N
Hydrofluoric Acid F N N
Hydrofluosilicic Acid G N G
Hydrogen E E E
Hydrogen Peroxide G F G
Hydrogen Sulfide, Dry E E E
Hydrogen Sulfide, Moist N F G
Kerosene E E E
Lacquers E E E
Lacquer Solvents E E E
Lactic Acid G N F
Lime E E E
Lime-Sulfur F G G
Linseed Oil G G G
Magnesium Chloride G N F
Magnesium Hydroxide E E E
Magnesium Sulfate E F E
Mercury N N N
Mercury Salts N N N
Methyl Alcohol E E E
Methyl Chloride, Dry E E E
Milk E G E
Mine Water F N F
Natural Gas G E E
Nitric Acid N N N
Nitrogen E E E
Oleic Acid G F G
Oxalic Acid G N F
Oxygen E E E
Palmitic Acid G F G
Paraffin E E E
Phosphoric Acid G N F
Potassium Carbonate E G E
Potassium Chloride G N G
Potassium Chromate E E E
Potassium Cyanide N N N
Potassium Dichromate Acid N N N
Potassium Hydroxide G F G
Potassium Sulfate E G E
Propane E E E
Rosin E E E
Sea Water G F E
Sewage E F E
Silver Salts N N N
Soap Solutions E G E
Sodium Bicarbonate G F G
Sodium Bisulfate G N G
Sodium Carbonate E G E
Sodium Chloride G N G
Sodium Chromate E E E
Sodium Cyanide N N N
Sodium Dichromate, Acid N N N
Sodium Hydroxide G F G
Sodium Hypochlorite F N F
Sodium Nitrate G F G
Sodium Peroxide F N F
Sodium Phosphate E G E
Sodium Sillicate E G E
Sodium Sulfate E G E
Sodium Sulfide F G G
Sodium Sulfite G N G
Sodium Thiosulfate F G G
Steam E F E
Stearic Acid G F G
Sugar Solutions E G E
Sulfur, Dry G E E
Sulfur, Molten N N N
Sulfur Chloride, Dry E E E
Sulfur Dioxide, Dry E E E
Sulfur Dioxide, Moist G N G
Sulfur Trioxide, Dry E E E
Sulfuric Acid G N F
Sulfurous Acid G N G
Tannic Acid E G E
Tar E G E
Tartaric Acid E F E
Toluene E E E
Trichloracetic Acid G N F
Trichlorethylene, Dry E E E
Trichlorethylene, Moist G F G
Turpentine E G E
Varnish E E E
Vinegar G N F
Water, Potable E N E
Zinc Chloride F N F
Zinc Sulfate G N G

Standard Conversions

Pressure (psi to kPa)
psi kPa kPa psi
1 6.9 1 0.15
2 13.8 2 0.29
3 20.7 3 0.44
4 27.6 4 0.58
5 34.5 5 0.73
6 41.4 6 0.87
7 48.3 7 1.02
8 55.2 8 1.16
9 62.1 9 1.31
10 69.0 10 1.45
50 345 50 7
100 690 100 15
250 1724 250 36
500 3448 500 73
1000 6895 1000 145
5000 34475 5000 725
10000 68950 10000 1450
20000 137900 20000 2901
50000 344750 50000 7252
75000 517125 75000 10877
100000 689500 100000 14503
Length / Distance
Metric Imperial Imperial Metric
1mm 0.0393 inch 1/8 inch 3.17mm
1cm 0.3937 inch 1 inch 25.40mm
10cm 0.3281 foot 1 foot 30.48cm
1m 1.0936 yard 1 yard 0.914m
1km 0.6214 mile 1 mile 1.61km
Temperature
Fahrenheit Celsius
0 -17.8
5 -15.0
10 -12.2
32 0.0
50 10.0
75 23.9
100 37.8
150 65.6
200 93.3
212 100.0
Pressure Conversion
lbs/in² kg/cm² kPa Bar
lbs/in² 1 0.07031 6.895 0.0689
kg/cm² 14.22 1 98.05 0.981
kPa 0.1451 0.0102 1 0.01
Bar 14.51 1.02 100 1
Imperial to Metric
Inches Inches mm Inches Inches mm
Fraction Decimal Fraction Decimal
1/64 0.016 0.397 33/64 0.516 13.097
1/32 0.031 0.794 17/32 0.531 13.494
3/64 0.047 1.191 35/64 0.547 13.891
1/16 0.063 1.588 9/16 0.563 14.288
5/64 0.078 1.984 37/64 0.578 14.684
3/32 0.094 2.381 19/32 0.594 15.081
7/64 0.109 2.778 39/64 0.609 15.478
1/8 0.125 3.175 5/8 0.625 15.875
9/64 0.141 3.572 41/64 0.641 16.272
5/32 0.156 3.969 21/32 0.656 16.669
11/64 0.172 4.366 43/64 0.672 17.066
3/16 0.188 4.763 11/16 0.688 17.463
13/64 0.203 5.159 45/64 0.703 17.859
7/32 0.219 5.556 23/32 0.719 18.256
15/64 0.234 5.953 47/64 0.734 18.653
1/4 0.250 6.350 3/4 0.750 19.050
17/64 0.266 6.747 49/64 0.766 19.447
9/32 0.281 7.144 25/32 0.781 19.844
19/64 0.297 7.541 51/64 0.797 20.241
5/16 0.313 7.938 13/16 0.813 20.638
21/64 0.328 8.334 53/64 0.828 21.034
11/32 0.344 8.731 27/32 0.844 21.431
23/64 0.359 9.128 55/64 0.859 21.828
3/8 0.375 9.525 7/8 0.875 22.225
25/64 0.391 9.922 57/64 0.891 22.622
13/32 0.406 10.319 29/32 0.906 23.019
27/64 0.422 10.716 59/64 0.922 23.416
7/16 0.438 11.113 15/16 0.938 23.813
29/64 0.453 11.509 61/64 0.953 24.209
15/32 0.469 11.906 31/32 0.969 24.606
31/64 0.484 12.303 63/64 0.984 25.003
1/2 0.500 12.700 1 1.000 25.400

Conversion Factors

Mass
From To Multiply by
ounce (oz) gram (g) 28.349
gram (g) ounce (oz) 0.035
pound (lb) kilogram (kg) 0.454
kilogram (kg) pound (lb) 2.205
ton tonne 1.016
tonne ton 0.984
Density
From To Multiply by
pound / cubic inch (lb/in³) gram / cubic centimetre (g/cm³) 27.679
gram / cubic centimetre (g/cm³) pound / cubic inch (lb/in³) 0.036
pound / cubic foot (lb/ft³) kilogram / cubic metre (kg/m³) 16.018
kilogram / cubic metre (kg/m³) pound / cubic foot (lb/ft³) 0.062
pound / cubic yard (lb/yd³) kilogram / cubic metre (kg/m³) 0.593
kilogram / cubic metre (kg/m³) pound / cubic yard (lb/yd³) 1.684
Pressure
From To Multiply by
pound / foot (lb/ft) kilogram / metre (kg/m) 1.4882
kilogram / metre (kg/m) pound / foot (lb/ft) 0.672
pound / square inch (lb/in²) kilogram / square centimetre (kg/cm²) 0.07031
kilogram / square centimetre (kg/cm²) pound / square inch (lb/in²) 14.22
pound / square inch (lb/in²) kilopascal (kPa) 6.895
kilopascal (kPa) pound / square inch (lb/in²) 0.145
pound / square inch (lb/in²) megapascal (MPa) 0.006895
megapascal (MPa) pound / square inch (lb/in²) 145.04
ton / square inch (ton/in²) megapascal (MPa) 15.444
megapascal (MPa) ton / square inch (ton/in²) 0.0647
bar kilogram / square centimetre (kg/cm²) 1.02
kilogram / square centimetre (kg/cm²) bar 0.981
bar pound / square inch (lb/in²) 14.51
pound / square inch (lb/in²) bar 0.0689
bar kilopascal (kPa) 100
kilopascal (kPa) bar 0.01
Temperature
From To Use Equation
centigrade (C) fahrenheit (F) (C. x 1.8) + 32
fahrenheit (F) centigrade (C) (F – 32) / 1.8
Length
From To Multiply by
thou. inch (µin) millimetre (mm) 0.0254
millimetre (mm) thou. inch (µin) 0.0393
inch (in) centimetre (cm) 2.54
centimetre (cm) inch (in) 0.3937
foot (ft) metre (m) 0.3048
metre (m) foot (ft) 3.2808
mile kilometre (km) 0.6213
kilometre (km) mile 1.6093
Volume
From To Multiply by
cubic inches (ci) cubic centimetres (cc) 16.3871
cubic centimetres (cc) cubic inches (ci) 0.061
cubic foot / min (cfm) litre / min (l/min) 28.3168
litre / min (l/min) cubic foot / min (cfm) 0.0353
cubic yard (yd³) cubic metre (m³) 0.7645
cubic metre (m³) cubic yard (yd³) 1.3079
fluid ounce (fl oz) ml (cm³) 28.4131
ml (cm³) fluid ounce (fl oz) 0.035
pint litre (dm3) 0.5682
litre (dm3) pint 1.7605
imperial gallon litre (dm3) 4.5506
litre (dm3) imperial gallon 0.2197

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