The instruments called pattern blocks are also called Johansson blocks, since their inventor was Carl Edward Johansson, who in 1888 worked as an inspector. The need for a new design of tools for inspection, had the idea of building rectangular blocks with fixed measures. Over time these blocks were called pattern blocks.
What are the pattern blocks?The pattern blocks are solid rectangular tools, capable of materializing a finished length with the highest precision. These pieces have a polish that guarantees excellent parallelism and fullness.
What are the pattern blocks for?As we mentioned in the previous paragraph, the pattern blocks serve to materialize a length and use it as its name indicates as a pattern. This allows:
- Know the error of the measuring machines .
- Calibrate the measuring machines based on the standard blocks.
Requirements that the standard blocks must meetFrom its creation until today the standard blocks were evolving, fulfilling different quality requirements. Today, the characteristics of these tools comply with ISO 3650 standards. The requirements to comply with this standard are:
- Dimensional and geometric accuracy . Must meet length, parallelism and flatness requirements.
- Adhesion capacity with other standard blocks. This quality is provided by the surface finish.
- Dimensional stability over time.
- Wear resistance
- Have a coefficient of thermal expansion similar to that of metals.
- Be resistant to corrision.
Types of pattern blocksThere are different types of pattern blocks depending on the material with which they are manufactured.
- Steel pattern blocks: They have great precision and dimensional stability. As for its coefficient of thermal expansion it is low. They must be protected from moisture and corrosion and must be cleaned properly after use.
- Hard metal standard blocks: They are usually made of tungsten carbide or lead. They offer a very good adhesion and are very resistant to wear.
- Ceramic pattern blocks: They have the highest wear resistance and adhesion and stability properties. They are made with zirconium oxide. It has the advantage that magnetic impurities do not adhere as if it can happen in the other parts which causes them to be damaged.
How to use a pattern blockThe standard blocks come together with many pieces in boxes where these blocks grow by 1 mm or 0.5 microns depending on the quantity of pieces they contain.
It happens that many times we want to perform a measurement and it does not exactly match the length of an individual block, so a standard block coupling process must be performed to achieve the exact measurement.
The standard blocks have the ability to adhere to each other by means of their faces. In this way they join each other until they reach the measure that they want to materialize.
Care of the pattern blocksAs we mentioned in previous paragraphs, when we talk about standard blocks we are talking about very high precision pieces. This means that special care must be taken every time a standard block is used. For this, the following points must be taken into account:
- Working in a working environment with temperatures near 20° C .
- Work on soft surfaces, always using gloves or tweezers, avoiding handling them with bare hands.
- After using the standard blocks, they must be cleaned and lubricated before being stored.