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The purpose of Gauge blocks is to provide a linear reference dimension to very close tolerance. Gauge blocks are used for calibrating measuring instruments, such as micrometers and calipers.
Gauge blocks are rectangular or square steel blocks with a very accurate width. They are sold in sets; a typical set has 91 pieces with widths varying from 0.010 to 0.100 in steps of 0.001.
Several blocks are stacked to give the required overall dimension. The surfaces of the blocks are extremely flat and highly polished. The blocks are placed together, so that the faces overlap, and then slid into alignment. This creates a vacuum between the faces that makes them stick together, they can only be disassembled with a sliding action. This method of stacking the blocks is known as 'wringing'
There are four grades of blocks:
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Application
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Grade
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above tolerance
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below tolerance
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| Reference |
AAA |
+0.00005mm |
-0.00005mm |
| Calibration |
AA |
+0.00010mm |
-0.00005mm |
| Inspection |
A |
+0.00015mm |
-0.00005mm |
| Workshop |
B |
+0.00025mm |
-0.00015mm |
Follow the link for more Measurement Methods and more about Measurement Systems.
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