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At Fastenright Ltd. we are able to stock or provide a variety of thread types for all kinds of fasteners – with some more popular in certain corners of the world than others.

It’s good to understand what you’re looking for in regards to thread – as each is used in a different way.

Thread Types and What Makes Them Different

Metric Thread

Metric thread is the most widely used today, and can otherwise be referred to as ‘ISO Metric’ or ‘M’.

They are available in both coarse and fine threads in a wide range of materials and sizes – with a number of popular DIN standards.

There are, of course, positives and negatives to fine metric thread and coarse metric thread. Fine metric threads are more susceptible to galling, need longer thread engagements and are less suitable for high-speed assembly. Fine threads are, however, able to be more easily tapped into hard materials, require less torque and have less tendency to loosen. They also are stronger, size for size than a coarse thread, and allow for finer adjustments because of their smaller pitch. Coarse threads are larger pitch and easier to obtain than fine thread fasteners, and they are specified for the majority of applications.

Metric threads come in a variety of strengths, in ‘grades’ ranging from 4.8, to 8.8, 10.9 and 12.9.


UNC stands for ‘Unified Coarse’ and is the most commonly used thread type in the United States of America.

It is often used within the agricultural industry because of their strong coarse threads.

The thread is deeper and more generic than that of a fine thread and allows for easy removal, whilst they also have a higher tolerance for manufacturing and plating.


UNF stands for ‘Unified Fine’, which is also a popular thread in the United States.

It is often used in the automotive industry because of the requirement of tight, fine threads. These threads are generally available with steel and stainless steel fasteners.

They host better torque locking and load carrying ability than their UNC counterparts.

Hosting a more specific fit, they have tighter tolerance and can also be found in the aerospace industry.


BA are also referred to as ‘British Association’ and are an old-style British thread with numbered diameters.

When we say it’s old-style, this thread has been around since 1884 and was standardised in 1903, and is mainly found in electrical fittings.

It is slowly being phased out in favour of metric threads.

This system is generally used on small screws.


BSF, or ‘British Standard Fine’ is another old-style British thread and can be used on vintage automobiles and machinery.

It is available in steel and stainless steel.

Bolts, nuts, screws and other fasteners can all be seen with BSF, and is a fine-pitch alternative to other threads.

Contact us for a Fastener with a Specific Thread Type

We are able to provide fasteners in any of the above thread types should you require it.

If you would like to further an enquiry, please contact us.