# How to Read a Depth Gauge

by Russell Wood

A depth gauge is a useful tool for determining how deep a hole or object is. It's more accurate than a tape measure or a ruler, plus it can give you the exact depth of the part you're looking at. So why is that useful? Let's say you want to measure the depth of your spark plug holes to make sure the plugs you're installing are correct, or you want to find out how much the distance is between the throttle body and throttle plate for potential modifications. Depth gauges are easy to use once you know how. In this case, the depth gauge will measure the depth of a socket, but you can use this for anything you want.

Place the depth gauge in your hands and locate each part. The main section is the ruler, which is how you'll be getting your measurement. Then there is a sliding panel that goes around the ruler, which has a wide platform that angles downwards into a flat section. When the panel is slid to the bottom of the ruler, the flat section of the platform is perfectly level with the end of the ruler. You determine your measurement by getting the distance between the platform and the end of the ruler.

Place the flat surface of the platform on the edge of the socket so the ruler is pointing straight up in the air. Make sure the flat surface of the platform is straight on the edge of the socket.

Push down on the ruler, sliding the ruler through the platform and towards the bottom of the socket.

Pick the depth gauge out of the socket, making sure not to move the platform, and look on the ruler. There are measurement marks on the ruler with hash marks. Find the hash mark that perfectly aligns with the flat section of the platform. That is the depth of the socket, and the measurement you would use for whatever task you need.