Language evolves as people adapt to improve its perceived usefulness.
I mention this term upfront to save irate letters from purists who decry the use of slang terminology due to problems it can create. My purpose in presenting the following is to make newcomers to the field aware of some terms they never learned in school. Similarly, those who are experienced in the field in another country may doubt their command of English when these terms pop up.
As any linguist will tell you, language is continually evolving from usage as people adapt to improve its perceived usefulness. The term ‘app’ for the word application is a contemporary example of this. The following terms are from a list of dozens that may be peculiar to a particular country or era that you may encounter.
Drop Down Gage: When I first heard this one I was stymied until I looked at what it was supposed to measure and then the lights went on. Basically, it refers to a dial indicator of AGD style that is used on comparator stands and other equipment all over the place. The indicator spindle drops down to contact the item being measured and that, I believe, is how the term came to be.
If you worked in England, old timers would refer to the same instrument as a ‘clock’ which, when you think about it, it does resemble. When they speak of ‘clocking up’ something, they are usually referring to a runout check.
Of course, there is the other type of indicator that does similar work using a long contact arm that acts as a lever for part of its amplification. This type is usually referred to as a ‘test’ indicator to differentiate from its larger sibling.
While these names came from their mechanical origins, they are still used but with the word ‘digital’ as a prefix to their more modern counterparts.
Gage Blocks: These well-known masters have a variety of names, the more popular being ‘jo’ blocks after the man who brought them to market, Carl Johansson. In England, old timers refer to them as ‘slips’ no doubt since you slide them together to build up a dimension. In North America, the term ‘hoke’ blocks is another type of gage block—soon to be 100 years old. While square in cross section today with a hole through their center, the original design was round.
Feeler Gages: In its generic form, these are very thin pieces or leafs of metal about 1/2” x 4” or 10mm x 100mm that are used to evaluate gaps between surfaces. They are available in sets from many makers. Some popular thicknesses are available in rolls and are referred to as shim stock, their usual purpose but they can also be used like their individual leaf cousins.
Regular reversible style go/no go plain plug gages are frequently referred to as feeler gages when they are used in conjunction with a fixture to check stampings, etc. The fixture usually incorporates pins located around the profile to be checked using the feeler type plug gages to check the gap between the edge of the work and the pins. Fixture makers usually leave a nominal gap between the two of .1” or 2mm or more to ensure the ‘feelers’ don’t get bent out of shape. A larger nominal gap enables measurements to be made using standard instruments when go/no go answers aren’t good enough.
As you can imagine, all manner of gages including rectangular shapes can be made to suit this work, so it is best to specify clearly what kind of ‘feeler’ you want.
Functional Size: This is a concept that causes all manner of problems. In its simplest form, it means a size that is perfect in all respects that will encompass the complete surface of the feature it refers to. This term comes into play when two mating parts are measured and appear to meet spec but will not assemble.
The reason for this is that, invariably, one or two measurements have been used to declare a ‘size’ for one or the other or both parts. The things that were not measured such as roundness or taper or straightness etc. are unknowns and are the reason for the problem. This problem arises quite often when it comes to screw threads since there are so many factors that affect it, some of which cannot be measured by most shops or labs—if any.