Gauge blocks are precision-machined blocks which are tailored for calibrating measuring equipment and to be used as professional precision measuring devices.
Also known as “Jo blocks”, after their designer, a Swede named Carl Johansson, they are manufactured in sets containing a range of different sizes.
- They are made this way so that they can be used in different ways to make up practically any wished for measurement, and up to several inches (1 inch = 2.5 cm)
Traditionally made from high grade steel or carbides which are able to withstand lots of wear and damage, the gauge block is machined with two sides which are perfectly flat and parallel to one another.
Various Precision Grades
This kind of precision measurement technology is manufactured in different grades, which all accord to precision. The lowest grades of gauge blocks have a precision tolerance of somewhere around25 millionths of a metre, which is about the same as a fine strand of human hair.
Whereas the highest grade of gauge blocks will have a precision tolerance as low as 0.05 millionths of a metre, which is a minute fraction of the thickness of a strand of a spider’s web.
What is Wringing?
Wringing is the technique of attaching the blocks together and involves placing a fine layer of oil between the blocks, which will then cause them to adhere to each other as if they were glued.
- You can separate the blocks by carefully sliding them apart, but it will take some considerable amount of strength
- A stack of gauge blocks that have been wrung together can easily support their own weight without falling apart
It is still not fully understood how this process actually happens, but it has been said to be a combination of molecular attraction, surface tension of the wring film, and possibly even some type of vacuum which has been generated between the blocks.
All About Lapping
What is called “lapping”, is a grinding and polishing process, and is put to use to make sure that the surface of a gauge block is extremely flat and smooth.
- For lower grade settings, the thickness of the wring film is so minute as to not be of any importance in measurement
Regarding the higher settings, for the more exact grades of gauge blocks, the length of the block is intentionally reduced by the thickness of one wring film, so when they are combined, the thickness of the layers of the wring film is not compromised by any amount of measurement.
So Many Uses
Professionals who use such precision equipment have discovered a number of uses for gauge blocks, such as calibrating apparatus and measuring devices.
The remarkably precise measurements which are made possible when using these devices, allow for extremely accurate calibration for micrometres and other types of precision measurement tools.
These amazingly can be put to use for accurately measuring and reading not just objects, but also distances.