Depth gages are used to measure the depth of holes, cavities, and other component features. They are available in various configurations, depending on the specific application. Depth gage categories include dial depth gages, digital depth gages, depth micrometers, thread depth gages, flush-pin gages, depth rules, combination depth angle gages, and Vernier depth gages. 

Dial depth gages displays data with a pointer or needle mounted in a graduated disc-dial. The dial indications dimensions and positions around or from a reference point. Examples of depth gage graduations are 10-0-10, 45-0-45, 4-0-4, 50-0-50. Dial display design options include clockwise and counter-clockwise rotation, one or multi-revolution capabilities, and an analog amplifier. With dial depth gages, the analog amplifier provides a remote, electronic equivalent to the mechanical display. 

Digital depth gages present metrological data in numeric or alphanumeric form. They often have data output capabilities that use serial or other formats. Digital readouts are precise digital displays that are integrated into dimensional depth gages. Depth micrometers are another type of depth gages with a digital option. Typically, depth micrometers are used for precision dimensional gaging. They are made of a ground spindle and an anvil that is mounted in a tee-shaped frame. Micrometer depth gages are also available in both scale and dial varieties.

Depth gages include thread depth gages, flush-pin depth gages, depth rules, combination depth gages, and Vernier depth gages. Thread depth gages measure the depth of the thread surface in a hole. Flush-pin depth gages are go/no-go functional gages that rapidly assess the depth of the opening. Depth rules allow quick assessment. Typically, depth rules are used in applications where precision is not a high priority. Combination depth angle gages indicate the depth and orientation of a hole. Vernier depth gages have gradations engraved or printed onto a surface (linear or drum). The main scale provides an indication of the gaged dimension to a standard precision level (eg.,tenths). The Vernier scale also allows an increased level of precision (eg.,thousandths).