Understanding Fastener Threads: Part 2

Date Posted:

September 22, 2017

Post Author:

Marsh Fasteners


Last Updated on July 1, 2020 by Marsh Fasteners

In our previous blog about understanding threaded fasteners, we covered the main differences between finely threaded fasteners and coarsely threaded fasteners. Now it’s time to focus on the various types of finely and coarsely threaded fasteners on the market. Of course, there’s more that you need to know. In the fine and coarse range of threaded catalogs, there are many options to choose from and some terms that you will need to understand. Taking the time to understand the various types of threads will help you to choose the right type of fastener for your specific application to suit the industry and environment in which the fastener will be expected to perform. This can save time and money and provide much-needed peace of mind when buying fasteners and making use of them.

Types of Threaded Fasteners

  • Unc – unified national coarse threads:
    The most common type of threaded fastener due to the easy removal and high tolerance rating without the need for cross-threading for assembly.
  • Unf – unified national fine threads:
    These fasteners have a closer fit and tighter tolerance. They can lock torque and therefore have a high load baring capacity which makes them an ideal fastener in the aerospace environment.
  • Unef – united national extra fine threads:
    These fasteners have an even finer thread than unf fasteners. This makes them appropriate for very specific applications: usually in those materials with tapped holes.
  • Unjc & unjf threads:
    These fasteners are typically heavy load bearing bolts used both internally and externally.
  • Unr & unk threads:
    These are coarser threaded and have a rounded root radius (unr). The unk has a smaller diameter and root radius.
  • Constant pitch threads:
    These fasteners are available in many different diameters and pitches and are typically bolts.

For more information on the various types of fine and coarse thread fasteners, we invite you to get in touch with us via email or telephone at Marsh Fasteners today.