1-Depth Gage and Combination Square - Steel Rule Depth Gage

The depth gage, not to be confused with the depth micrometer, is an adaptation of the steel rule (aka scale) with an attachment head. Although there are several designs of this tool two of the most common are the shown below.

Regular Head: the rule is fixed perpendicular to the base but can slip through a slot in the base.

Protractor Head: The same as Regular Head Depth Gage with angles of 30, 45, 60 degrees etched in both sides. There is no angle adjustment. These etched lines are for reference only. Due to the lack of vernier graduations high accuracy should not be expected.

Both gages have the same function: to measure grooves, holes, recesses, and steps. They can be used much quicker and can fit in smaller places than a depth micrometer. Most common gages have a 1/8" blade that may or may not be graduated. Gages with blade are graduated in 32nd and 64ths or in 64ths and 100ths of an inch. This thin 1/8, 6-inch blade is held in a groove by a lock nut. The graduation rule may be used separately from the head.