Depth measuring instruments are tools used to accurately measure the depth of holes, recesses, slots, or other features in a workpiece. These instruments are commonly used in manufacturing, machining, woodworking, and other applications where depth measurements are crucial. Here are some common depth measuring instruments:

1.     Depth Gauge: A depth gauge is a versatile instrument used to measure the depth of holes, slots, or recesses. It consists of a base or rod with a scale or digital display, and a probe or rod that is inserted into the feature being measured. The depth gauge provides a direct reading of the depth measurement.

2.     Depth Micrometer: A depth micrometer is a specialized micrometer used specifically for measuring depth. It is similar in design to an external micrometer, but it has a flat base and an extended spindle to reach the bottom of the hole or feature. Depth micrometers have a scale or digital display that provides the depth measurement.

3.     Digital Caliper with Depth Rod: Many digital calipers come equipped with a depth rod or extension rod that allows them to measure depth in addition to length and other dimensions. The depth rod is attached to the caliper and can be used to measure the depth of holes or recesses. The digital caliper displays the depth measurement directly.

4.     Depth Indicator: A depth indicator, also known as a depth probe or dial indicator, is a mechanical measuring tool used to measure depth. It consists of a probe or stylus attached to a dial indicator or digital display. The probe is placed into the feature being measured, and the indicator displays the depth reading.

5.     Vernier Depth Gauge: A vernier depth gauge is a traditional mechanical depth measuring instrument. It is similar in design to a vernier caliper but has an extended rod or blade for measuring depth. The vernier scale allows for precise depth readings.

6.     Bore Gauge: A bore gauge, also known as a bore micrometer, is used to measure the diameter and depth of holes or bores. It consists of an expanding mechanism that fits into the hole and provides a measurement of both the diameter and depth.

7.     Laser Distance Meter: While primarily used for distance measurements, laser distance meters can also be used to measure depth by using the Pythagorean theorem. By measuring the distance from the surface to the bottom of the hole and subtracting the thickness of the material, the depth can be determined.

When using depth measuring instruments, it is important to ensure proper contact with the feature being measured and to take multiple readings for accuracy. Regular calibration and maintenance are also necessary to ensure the continued accuracy of the instruments.