Most measuring instruments, production aids and tools in the industry have been manufactured in the last 10 years or perhaps in the last 20 years. We often call, a little carelessly, those who are older than that antique or just really old.

But did you know that there are things that are "made" more than a billion years ago and that are used daily in many companies! OK, a bit pointed statement maybe, but still not wrong. Of course, we are talking about granite or diabase surface plates.

What is a surface plate?

Simply put, it is a large plate made of stone, from small plates that do not weigh more than a few kg to large thick plates that weigh several tons. The idea with a surface plate is that it should be absolutely flat and smooth and not change anything in shape.

The material for the surface plate is mined in quarries and then ground to a very high degree of accuracy. The finest plates have a flatness deviation of less than 2 µm. If you want, you can see it as if the surface plate has been down there in the ground for maybe a billion years and only needed to be ground up to be used!

It is used for precision work and measurements where flatness and horizontality are an absolute must. As an example, it can be mentioned that when using and also calibrating the height gage, a level plate is needed. Another example is that you can check angles with the help of a level plate. The uses are endless.

Surface plates are also included as part of other instruments, in stands or in coordinate measuring machines, for example.

Then we come to the chapter on calibration.

Such a fantastically stable thing as a surface plate does not need to be calibrated, right? Yes indeed! A surface plate can for various reasons stop being flat, for example due to wear.

When calibrating, the plate is first cleaned very thoroughly, so that all possible deposits and dirt disappear. It is aligned and then the plate is measured at a large number of points using a special calibration equipment.

Take good care of your granite surface plate! If you clean it occasionally and are not too violent, you can probably use it for a few million more years!

P.S. If you have any questions or need any help, please send inquiries to This email address is being protected from spambots. You need JavaScript enabled to view it.

Erik Stenström