To measure bolt head size with a tape measure, focus on determining the distance across the flats (the widest part of the bolt head). Here's how:
Steps for Measuring Bolt Head Size
-
Identify the "Flats": The flats are the parallel sides of the bolt head, typically a hexagon shape.
-
Position the Tape Measure: Place the tape measure across the bolt head so that it spans from one flat side to the directly opposite flat side.
-
Read the Measurement: The measurement you obtain is the distance across the flats. This is the standard way to specify the bolt head size and corresponds to the size of wrench or socket needed to tighten or loosen the bolt.
-
Ensure Accuracy: Make sure the tape measure is straight and that you're measuring the widest distance across the flats. Avoid measuring corner-to-corner, as this will give you an inaccurate reading.
Why Measure Across the Flats?
Measuring across the flats provides a consistent and reliable method for identifying bolt head sizes. This measurement is directly related to the size of the wrench or socket required to work with the bolt. This is especially important because bolts are specified this way.
