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Quick guide for use and maintenance of gauge blocks.

June 04, 2021
Quick guide for use and maintenance of gauge blocks.

Introduction:

Precision Gauge Blocks are master standard tools vital for dimensional quality control in the manufacturing of machined parts and/or products. As their name indicates, the gauge blocks are usually rectangular or cubic pieces made of steel alloys, ceramic (usually zirconium), or even tungsten, which serve as dimensional references of linear distances, measuring between 2 of their opposite faces. Each type of material offers different benefits, as well as different costs to cover all the precision needs in dimensional assessment work.

Grades and Applications:

There are several international classifications that define the precision of commercial gauge blocks, and manufacturers must have the ability to trace their manufacturing process to national or international laboratories that certify the geometric and tolerance values of the products. Japan's Mitutoyo Corporation is able to trace its gage block production process to the national laboratories NMIJ (National Metrology Institute of Japan), the NIST (National Institute of Standards and Technology) in the United States, and the CENAM (National Center for Metrology). in Mexico, among many others internationally.

Grade types and their recommended use:

  • Grade 2: Use in general processes and workshops.
  • Grade 1: Use for specialized mechanical inspection and calibration of electronic or digital measuring instruments.
  • Grade 0: Use in the calibration of other blocks or high precision instruments in controlled temperature environments and/or controlled conditions.
  • Grade K: Scientific or very high precision use under highly controlled conditions (temperature, humidity, cleanliness).

Differences between materials:

The most common materials are alloy steel, ceramic, and tungsten alloy. Each material offers different mechanical and thermal properties, as well as degrees of geometric tolerance, and varies greatly in cost, with ceramic being usually the most expensive, but at the same time those with less thermal expansion and more resistant to damage such as scratches or burrs. , while those made of steel are usually the most affordable, although more susceptible to variations in temperature or physical damage.


Using the gauge blocks:

Gauge blocks are usually available in sets of, from 2 or 3 tens to more than 100 pieces, and in steps of up to a tenth of a micrometer (depending on the degree), that is 0.0001 mm (one ten thousandth of a millimeter). Although one could be tempted to achieve as many steps as models, the most appropriate thing is to verify which are the measures that will be reviewed the most and look for the most flexible combination of pieces to achieve these measures; Find the smallest and largest measure you need and evaluate the number of steps that best approximates the intermediate measures you will use.

In order to achieve intermediate measures, what is done is to join blocks of different measures until the necessary height is achieved. To join the blocks a process referred to as wringing in English is used, which can be translated as "twisting". To join blocks, we first have to select from highest to lowest the blocks that would be needed; For example, to achieve a height of 45.6785mm the following blocks (in mm) would be used: 25 + 17.5 + 1.17 + 1.008 + 1.0005.

How to put gauge blocks together:

Before you begin, take the following considerations: Try to use the minimum amount of block possible.

0.- Remember to allow time for thermal stabilization if you are not working in a controlled temperature environment.

1.- Clean the measuring faces and check the faces for burrs with an optical plane. If necessary, clean the surfaces with Cerastón * stone for block maintenance.

2.- Apply a small amount of oil on the measuring face and distribute it evenly. Wipe until layer is practically removed; a minimal film will remain on the surface. Use a thin mechanical oil to avoid leaving residue.

3.- Gently put the faces of the gauge blocks in contact, with different techniques depending on the size of the gauge blocks:

  • a) Thick blocks: contact the faces of the blocks perpendicular to each other, then rotate both blocks applying light pressure (you will feel the blocks come together) and finally align the measuring faces.
  • b) Thick Block with Thin: Place the edge of the thin pattern over one end of the thick pattern, slide the thin pattern over the thick while pressing the surface to align them.
  • c) Thin blocks: it is important to have first aligned a thin one over another thick one to prevent bending, then repeat the steps as in point b) and finally remove the thick one if you will not use it.

Check the adhesion status with an optical comparator. Repeat the steps as necessary.

Maintenance:

Let us remember that blocks are commonly used to verify linear geometry standards within manufacturing companies, so the reliability of the measurements is a priority, and keeping the gauge blocks in good condition should be a daily task, as problems such as corrosion, a buildup of burrs or debris or mistreatment of parts can seriously compromise results. Scheduled maintenance, as well as annual material certification, is the key to ensuring consistency in measurements.

Recommended steps for block maintenance:

  • Remember that master blocks are high precision instruments and as such, they require to be handled by personnel trained in their use.
  • Always store the blocks in their corresponding case and in a dry place and not exposed to the sun.
  • Handle your blocks with cotton gloves or latex gloves to avoid an accumulation of grease and/or sweat on the surfaces of the blocks.
  • To remove dirt from the block surface using compressed air and soft brushes; for tougher items, you can use a cleaning solution such as alcohol solutions, such as those used to clean lenses or optical or electronic items and leave no residue when evaporating, and optical cleaning paper to avoid scratches.
  • Finally, use CERASTON stone (alumina stone) from Mitutoyo to remove burrs and accumulated elements that are not easily removed by other processes, in conjunction with solvent elements.
  • Check with an optical flat lens to check for burrs on the block.

For more information contact your Yamazen sales representative or send an email to info@yamazen.com.mx.

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