[April 1, 2016]
Many people consider the planer gage to be an obsolete tool with no practical use in today's machine shop. In fact they are still made today, although they can also often be picked up at a bargain price at a flea market, garage sale, or other places used tooling is sold. The planer gage was originally intended to be used to set the cutter height on a metalworking planer or shaper (here is the Starret patent from 1916), but it has many other uses.
This photo shows a planer gage I picked up at an estate sale for $20 (Sept. 2015).
Starret refers to this gage as a Universal Precision Gage No. 995 - this nomenclature recognizes the fact that the gage has many uses beyond its original intent. It is distinguished from "basic" planar gages by the inclusion of the following:
This gage is also referred to by some as a "master planer gage." This comment from Hugo F. Pusep (writing in American Machinist, 1916, pp. 1131) is applicable not only to the planer gage, but likely to many other tools as well:
It is often the case that a tool, because of its simplicity and because it was originally made for a single purpose, is used for nothing else - not because it lacks adaptability, but simply because no one thinks of other applications.
Here are a few if the applications which people have found for this tool: