External thread - Male thread – chart, sizes

Main image for the article about external male threads

What is an external thread?

An external thread is a variation of a thread that has a coiling on the outside. It is most commonly found in the form of a screw, but no less common are external pipe threads, i.e. those found on pipe joints that are later bolted together into a single structure.

External Threads Examples - Male Threads Examples

What is the difference between the external thread and internal thread?

The main difference between external thread and internal thread is the location of the coiling. External threads have coiling on the outside, and internal threads have the coiling is on the inside.

It is worth mentioning that an external thread is also referred to as a 'male' thread - in contrast to the internal thread, which is the female part. This means that the former screws into the latter.

Thus, the external and internal threads together form a solid joint, just like, for example, a screw and a nut.

What are the dimensions of external male threads? External threads chart

The chart below shows the most important dimensions for common threads:

External thread Thread pitch Metric BSP UNF NPTF
thread size in mm   Typical metric (European) threads Typical British inch threads Typical US threads US tapered
9,3-9,7 28/inch   1/8''-28    
9,3-9,7 29/inch       1/8''-29
9,7-9,9 1.5 mm M10x1,5 M10X1      
10,9-11,1 20/inch     7/16''-20  
11,6-11,9 1.5 mm M12x1,5      
12,4-12,7 20/inch     1/2''-20  
12,9-13,1 19/inch   1/4''-19    
12,9-13,1 18/inch       1/4''-18
13,6-13,9 15 mm M14x1,5      
14,0-14,3 18/inch     9/16''-18  
15,6-15,9 15 mm M16x1,5      
16,3-16,6 19/inch   3/8''-19    
16,3-16,6 18/inch       3/8''-18
17,2-17,5 16/inch     11/16''-16  
17,6-17,9 1.5 mm M18x1,5      
18,7-19,0 16/inch     3/4''-16  
19,6-19,9 15 mm M20x1,5      
20,3-20,6 16/inch     13/16''-16  
20,5-20,9 14/inch   1/2''-14   1/2''-14
21,6-21,9 15 mm M22x1,5      
22,0-22,2 14/inch     7/8''-14  
22,6-22,9 14/inch   5/8''-14   5/8''-14
25,2-25,5 14/inch   1''-14    
23,6-23,9 1.5 mm M24x1,5      
25,6-25,9 1.5 mm M26x1,5      
26,1-26,4 14/inch   3/4''-14    
26,6-26,9 12/inch     1.1/16''-12  
26,6-26,9 2 mm M27x2      
26,6-26,9 1.5 mm M27x1,5      
29,6-29,9 2 mm M30x2      
29,8-30,1 12/inch     1.3/16''-12  
29,6-29,9 1.5 mm M30x1,5      
33,0-33,2 11/inch   1''-11    
32,6-32,9 2 mm M33x2      
32,6-32,9 15 mm M33x1,5      
33,0-33,3 12/inch     1.5/16''-12  
32,9-33,4 11.5/inch       1''-11.5
36,2-36,5 12/inch     1.7/16''-12  
35,6-35,9 2 mm M36x2      
37,6-37,9 1.5 mm M38x1,5      
40,9-41,2 12/inch     15/8''-12  
41,6-41,9 2 mm M42x2      
41,5-41,9 11/inch   1 1/4''-11    
41,4-42,0 11.5/inch       1 1/4''-11.5
42,5-42,8 12/inch     1.11/16''-12  
44,6-44,9 2 mm M45x2      
47,3-47,6 12/inch     1.7/8''-12  
47,4-47,8 11/inch   1 1/2''-11    
47,3-47,9 11.5/inch       1 1/2''-11.5
50,5-50,8 12/inch     2''-12  
51,6-51,9 2 mm M52x2      
59,2-59,6 11/inch   2''-11    

How to measure an external thread?

You can measure the male thread easily using a calliper. Grip it with the jaws so that they rest on top of the coiling and read the result. Then compare the reading with the data in the table, and you will know which thread you are dealing with.

The thread pitch will also be measured using a calliper. You will most conveniently do this as follows:

  • rest the jaws on the coiling along the thread, 
  • place 10 thread pitches inside the jaws, 
  • read the measurement and divide it by 10, 
  • the result is your thread pitch.

How do you make an external thread?

You will make an external thread in three ways:

  • on a lathe, a milling machine or a grinding machine, 
  • using a screwing die, 
  • using a special rolling mill.

The first option requires the ability to operate any of the devices mentioned - well, the device itself. Therefore, we will not focus on it.

The second way is much simpler, as it only requires the purchase of a screwing die, a special device for threading. It looks like a nut and is used similarly.

You simply screw the screwing die onto the threaded rod and its internal blades will cut the thread. The screwing die can either be manual or automatic (e.g. for a lathe).

The last method is the rolling mill, which is used for plastic threading. This means that it bends the thread into the plastic instead of cutting it out. However, it is not used very often.

How to repair an external thread?

You can repair an external thread with two different tools:

  • screwing die, 
  • thread file.

We have already mentioned the screwing die as a tool for producing threads, but it is also good for repairing or correcting them if they have been done badly. However, here it is very important to choose the right tool (in terms of size and model), so it is advisable to seek the help of a specialist.

On the other hand, if the thread damage is traced, you will remove it with a thread remover file. This is an inexpensive and easily accessible tool with which you can repair, for example, deformed coils.

Photo of Bartosz Kułakowski - CEO of Hosetech sp. z o. o.

Articles author

Bartosz Kułakowski

CEO of Hosetech Sp. z o.o.

Bartosz Kulakowski is an industrial hoses and couplings specialist with over 10 years of experience. Bartosz has been present in the technical industry since 2013. He gained experience as a technical and commercial advisor in the sector of plastic conveyor belts, steel structures, industrial hoses, and connectors. Since 2016, he has specialized exclusively in hoses and connectors. In 2019 he opened his own business under the HOSETECH Bartosz Kulakowski brand and since July 2022 he has been the CEO of the capital company HOSETECH Sp z o. o. (LLC).


What is an external thread?

What is the difference between the external thread and internal thread?

What are the dimensions of external male threads? External threads chart

How to measure an external thread?

How do you make an external thread?

How to repair an external thread?