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1-2-3 block
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English
thumb|A 1 times 2 times 3 inch steel block commonly used as a square reference or mount point when milling
Noun
1-2-3 block
A tool used in machining fields, especially milling, to aid in setup. It is a block of steel that is precisely squared and parallel whose sides are 1, 2, and 3 inches long, respectively. May contain arranged holes. Similar, larger blocks are called 2-4-6 blocks.
en setup block machinist block