Comparison – coarse vs fine threads

Whether to use Coarse or Fine Threads has been a subject of much debate. The following information lays out some advantages & disadvantages so that the reader can make up his own mind based on individual requirements. It should be noted however that the availability of standard coarse threaded fastener far exceeds fine threads fasteners, making them very cost effective. This argument together with the favorable economics of simplification has led to a bias in favor of coarse threads.

Coarse threads advantage for most applications:

  • Easier and faster to assembly components with less chance of cross threading.
  • Minor damage to threads during handling and shipping are less likely to affect assembly.
  • Less prone to stripping when fastened into lower strength materials.
  • Thicker plating possible because of relatively larger threads allowances and therefore less likely to seize in corrosion prone applications.
  • Better fatigue resistance because of less concentration of stress at thread root radius.

Fine Threads offer:

  • Higher strengths in tension because of larger tensile stress area.
  • Shorter thread depth allows threading in thin wall application.
  • Fine threads allow more precise adjustment because of smaller helix angle.
  • Where length of engagement is limited, fine threads provide greater strength.
  • Fine Threads are easier to tap in harder materials.
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