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Bolts and Nuts

The Basics​

A solid understanding of fasteners like bolts and nuts is crucial for building robust and reliable robots. This guide provides a quick reference for the common types of bolts and nuts used in Argos, how to identify them, and when to use each one.

What is a Bolt?​

A bolt is a type of fastener with an external male thread. Bolts are used to assemble two or more unthreaded components, with the help of a nut.

What is a Nut?​

A nut is a type of fastener with a threaded hole. Nuts are almost always used in conjunction with a mating bolt to fasten multiple parts together. Most nuts have six sides, so you can easily turn them with a wrench.

Bolt Naming Overview​

Understanding how bolts are named is key to identifying them correctly. Here's a breakdown of the components of a bolt's name:

  1. Diameter: How thick the bolt is.

    • Larger bolts (1/4" and up): Measured in fractions of an inch (e.g., 1/4", 1/2").
    • Smaller bolts (under 1/4"): Uses a number system from #0 to #12. A bigger number means a bigger bolt.

  2. Threads Per Inch (TPI) & Thread Type: This tells you how many threads (grooves) are in one inch of the bolt's length and indicates whether the thread is coarse or fine.

    • Coarse Thread (UNC): Fewer threads per inch (lower TPI). More common and easier to assemble.

    • Fine Thread (UNF): More threads per inch (higher TPI) for the same diameter. This provides a stronger hold and is better for applications with vibrations.

  3. Length: How long the bolt is, measured in inches from under the head to the tip for most common bolts.

Putting It Together​

You'll see sizes like "1/4-20 UNC x 1" or "1/4-28 UNF x 1". Here's what that means:

  • "1/4" is the diameter.
  • "-20 UNC" means 20 coarse threads per inch.
  • "-28 UNF" means 28 fine threads per inch (for the same 1/4" diameter).
  • "x 1" means it's 1 inch long.

So, you primarily need to know Diameter - Threads Per Inch (which indicates Coarse/Fine) - Length. For the same diameter, a fine thread bolt will have a higher TPI number.

Argos Bolt Quick Guide​

Here's a quick guide to selecting the right bolts for different applications on our team:

  • Competition Robot? Use 10-32 Bolts.

    • These are #10 size bolts with 32 threads per inch (a fine thread).

    • Think: Fine threads for the Final robot – they hold tight!

  • Prototyping with 80/20? Use 1/4-20 Bolts.

    • These are 1/4 inch thick bolts with 20 threads per inch (a coarse thread).
    • Think: Coarse threads for construction and quick changes with 80/20.

  • Exceptions

    • For the end of shafts, we use 1/4" bolts.

Argos Nut Quick Refrence​

We commonly use 3 types of nuts:

  • Nyloc Nuts: A nyloc nut is a special kind of nut designed to resist loosening. It has a plastic ring inside that squeezes the bolt threads, making it harder for the nut to vibrate off.

    • You can identify them by the colored plastic ring inside one end of the nut.

    • Should not use Loctite with nyloc nuts, as it can damage the nylon insert.

    • Good to know: The bolt needs to go all the way through the plastic part for it to work correctly. They can be reused, but may lose some grip over time.

  • Rivnuts: These are threaded inserts that are installed into a material (like a piece of tubing) to provide a threaded hole. They look like a rivet with threads on the inside.

    • Should use Loctite to secure the bolt within the rivnut.

  • Standard Nuts: These are the basic nuts with internal threads that screw onto a bolt. They typically have a hexagonal shape and no special inserts or features for locking.

    • Should use Loctite to prevent them from loosening due to vibration.