When it comes to fasteners, threads are key. Threads determine how well fastener components (like nuts, bolts and screws) hold materials and machines together, and maintain their integrity over time. The two main types of threads are coarse and fine, and while both types have their advantages and appropriate uses, coarse threads typically win in our book. Read on to learn the basics of these two types of threads and when you might consider using them in your applications.
The Basics of Threads
First, some definitions. Fine threaded bolts have a smaller pitch, meaning more threads per axial distance than coarse threaded bolts. Fine threaded bolts can also gall (when metallic surfaces slide against one another and friction and adhesion cause material to be pulled from one surface and then adhered to the other) more easily than coarse threads, and they are often harder to obtain.
Coarse threads are typically called for in most industrial applications, particularly in aviation and military situations, due to a variety of advantages.
Pros of Coarse Threads:
- Greater resistance to stripping and cross-threading
- Faster installation than fine threaded fasteners, partially because they aren’t prone to seizing during tightening. This can result in significant time and money savings in high volume assembly applications.
- Fine for most applications unless otherwise specified.
- Fewer assembly problems and less gaging because there’s less plating build-up between each thread flank
- Less galling with stainless steel threaded fasteners
- Better tapping into brittle materials–less likely to cross thread
- More tolerant of abuse
- Faster assembly and disassembly than fine threads
- Increased tolerance to thicker platings and coatings before thread adjustments are needed
When working with stainless steel, aluminum, titanium and other alloys, fine threads are preferable, particularly because of their strength.
Pros of Fine Threads:
- Stronger in both tension and shear due to larger stress area and minor diameter
- Allow finer adjustments in applications–ideal for sensitive assemblies
- Require less torque for tightening
- Less likely to loosen under vibration
- Can be more easily tapped into hard materials and thin-walled tubes
Buy The Highest-Quality Fasteners at Global Certified Fasteners
Still unsure what type of thread is right for your project? Contact the fastener experts at Global Certified Fasteners at (708) 450-9301 or sales@gcfasteners.com and we’ll be happy to help you find what best meets your application’s requirements.