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AN THREAD

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"AN" (Army-Navy) Sizes were established by the Aerospace industry years ago and were designated O.D. of the rigid metal tube that each size fitting is used with. 

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"AN" SIZES

The numbers assigned equate to the O.D. (outside diameters) of the tubing in 1/16".  Since tubing and hoses are to be found with assorted wall thicknesses, we can now understand that the designated size number does not necessarily tell you how large the inside diameter will be.  (For example, the inside diameter of an Earl’s size 6 hose end is nearly as large as the inside diameter of some other manufacturers’-8 hose ends.

Each AN size number has its own standard thread size, which can be seen in column three of the chart.  Again, these are the same thread sizes that have been used in aircraft and industrial applications for many years.

(The chart to the right will clarify this point). 

AN Size

Metal Tube O.D.

Thread size

2

1/8

5/16-24 SAE

3

3/16

3/8-24 SAE

4

1/4

7/16–20 SAE

5

5/16

1/2-20 SAE 

6

3/8

9/16-18 SAE

8

1/2

3/4-16 SAE

10

5/8

7/8-14 SAE

12

3/4

1-1/16-12 SAE

16

1

1-5/16-12 SAE

20

1-1/4

1/5/8-12 SAE

24

1-1/2

1-7/8-12 SAE

28

1-3/4

2-1/4-12 SAE

32

2

2-1/2-12 SAE

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 "NPT" THREAD SIZES:
Some of the most popular adapter fittings shown in our on-line shop are AN to NPT adapters 

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"NPT" SIZES

 While many variations are offered, column four in the chart shows which AN size corresponds to each NPT size when inside diameters (flow dimensions) are considered.

All Earl’s SWIVEL-SEALTM hose ends are designed to provide little or no restrictions when used with the corresponding AN fitting size.

We also offer a number of Metric and British Standard Pipe threads to AN fitting adapters.

Pipe Thread Size

Threads Per Inch

Theoretical I.D. of Ftg.

Closest AN Ftg. Size

1/16

27

1/16

-

1/8

27

1/8

4

1/4

18

1/4

6

3/8

18

3/8 

8

1/2

14

1/2

10

3/4

14

3/4

12

1

11-1/2

1

16

1-1/4

11-1/2

1-1/4

20

1-1/2

11-1/2

1-1/2

24

2

11-1/2

2

32