Benefits of Metric fasteners over Imperial, why Metric fasteners are widely use in world industry?


inch vs metric fasteners banner

    You guy may curious why there are both Metric and Imperial fasteners in the world, also which one should we select to use with our product then. Today, I will share some of my thought about this issue to you guys.

    For fasteners in the world there are generally 2 measurement units which are Metric system and Imperial system.

Metric system uses measurement unit such as mm(Millimeter) or cm(Centimeter)

for example, Socket Cap Screw M12x1.75px50

Imperial system uses measurement unit such as inch or feet

for example, Socket Cap Screw ½”-13 x 2”

    Then what are their differences? Both of them can convert their sizes to each other but actually there are some significant different in detail which is their thread measurement system.


Imperial system will use TPI (Threads Per Inch) which will measure how many threads will be in 1 inch(25.4mm) for example, Socket Cap Screw ½”-13 x 2”; This screw will have 13 threads per 1 inch for as UNC (Unified coarse) in other word, a normal thread for imperial system.

Metric system will use Thread Pitch, which will measure the range of major diameter between thread. for example, M12x1.75px50 will have a distance between each thread = 1.75mm

    Looking from outside they may look the same at the thread part, even when you measure them with vernier caliper for the nominal diameter, result might come out closely to each other for example M12 screw, you may measure them as 11.88mm as well as ½”Screw. They are even be able fasten to each other female nut or measurement unit but they are not perfectly fit to each other, some of them will be too tight or too loose. So we have to use pitch gauge to measure their sizes correctly. 

Well, Let’s talk about benefits of Metric fasteners then

1.       Metric fasteners are widely use globally since 18th century from France to the world

    Imagine every country that you are going to visit, they are all using different method of measurements same as currency, how much complicated it will be?  International Bureau of Weights and Measures which is established in late 18th century decided the standard to control measurement standard for the world. Then, Metric system turned to be one of the global standard. Most of the countries are applying Metric system except United State of America and other few countries in the world who are applying Imperial standard.

    If you have project to create some machine or product which might be related to other countries, You may have to consider about applicable fasteners standard at your destination country as well to prevent misunderstanding of measurement and also fasteners sourcing problem.

    Select common standard, will help you to work and collaborate with other parties around the world easier.

2.       Prevent difficulties of measurement conversion and misunderstanding

    Not all countries are get used to Imperial size if they are not in the related business or have been taught from the school but most of us get used to Metric system which we are even facing in our daily life as well For example, when we are going to measure our height we will know our height as cm. unit or when we are going to inform the distance between place we will say it in km. unit

    Most of people might take time to convert Imperial to Metric in other word Inch to mm in fasteners business, also sometimes misunderstanding or mistake could be occurred from this. Especially, if your products are related to precision parts which every mm are concerned point.

     For example, if you are manufacturing some product in Japan with Imperial system, you might find some difficulty to find tools or parts that fit to your product because Japan is using Metric system. Even there are some Imperial size tools or parts available but they are not widely distributed and could be expensive due to low market demand.

    It is better to know what your business are and whom you are going to deal the business with, this factor will help you to decide which standard you are going to use. Not to think just at the present but at the maintenance time as well. Globally designed product will take advantages of cost reduction and even make better user satisfaction. 

I will explain deep detail of each metric and imperial fasteners in upcoming issue, please stay tune with us.

Also, if there are any issue you would like us to write, please feel free to contact us.



Written by

Mr.Nuttapol Sirilert

International Sales Dept.

Hanshin Neji Co.,Ltd.