How to Measure a Hex Bolt

What You'll Need
Measuring Device

The hex bolt is one of the most common types of fasteners that are being used in a lot of mechanical processes. This is especially true when talking about auto mechanics. The hex head is easy to distinguish with its blocky type head that wrenches and sockets can get a good grip on. Replacing a hex bolt is still somewhat confusing among a lot of DIY mechanics. Here are the steps to measure a hex bolt for replacement.

Step 1: Measure Shank

The first measurement that you will need to take is the overall length of the shaft of the bolt. Place the tape measure directly underneath the head of the bolt and measure the shaft. 

Step 2: Measure Unthreaded Area

Most hex bolts have an area that does not have threads. Measure this, as you will need to make sure the replacement has the same measurement.

Step 3: Measure Bolt Diameter

Measure across the bolt to find its diameter. This should be across the threaded section of the bolt. 

Step 4: Count Threads

Measure one inch of the bolt and then count the threads in that section. This will give you the thread count of the hex bolt.

Step 5: Make Note of Grade

There will be a mark on the hex bolt that will signify its hardness. This is important when looking at a replacement hex bolt. Once you find this, you will have all the measurements you need for a new hex bolt.