How to Identify a Bolt

The parts of a Bolt H indicates the head G indicates Grade or hardness L indicates Length Diameter indicates the Size of the bolt Pitch indicates thread size Number of threads per inch on Standard bolts Distance between threads on a Metric bolt measured in Millimeters

A Scale (or Ruler) is used to determine the dimensions of a bolt.

One Side is Inches and the other is Millimeters

The 16th Scale is easier than the 32nd Scale for measuring Fractional bolts.

Step 1 Determine if the bolt is Metric or Standard

Is this metric or standard

Is this metric or standard?

Step 2 is to determine the Size Size means the diameter of the bolt across the threads.

What is the size of this standard bolt?

What is the size of this metric bolt?

Step 3 is to determine the thread pitch. Pitch means the number of threads per inch for a standard bolt. Pitch means the distance between threads for a metric bolt.

Thread pitch is measured with a thread pitch gage

What is the pitch of this metric bolt?

What is the pitch of this standard bolt?

Step 4 is to measure the length Length is measured from the bottom of the head to the end of the thread

What is the length of this standard bolt?

What is the length of this metric bolt?

The 5th step is to determine the Head size. Head size is measured from flat to flat.

What is the head size of this metric bolt?

What is the head size of this standard bolt?

If the threads are damaged what tool is used to repair them?

Die

Die Size Standard Die Size – Pitch Example: 3/8 – 14 Metric Die Size – Pitch Example: 10 X 1.25

Head Size

= number of threads per inch Standard Bolt Sizing Length Bolt Size Head Size Pitch = number of threads per inch

= distance between threads in mm Metric Bolt Sizing 8.8 Length Bolt Size Head Size Pitch = distance between threads in mm