How to Find the Tap Size for a Bolt
- 1). Look on the blades of the thread gauge to see if the measurements are metric or imperial. Most modern thread gauges will indicate both. These figures relate the threads per centimeter or threads per inch, which is turn relate to the size of the bolt.
- 2). Place any of the thread gauge blade in the threads of the nut. Repeat this until a blade is found that fits tightly in between the teeth of the thread.
- 3). Read the number on the side of the correct blade and select the corresponding die to go in the tap wrench.