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Woodworkers have brass setup bars for precision setup — machinists have gauge blocks.  You stack a series of gauge blocks to match the desired measurement, for accurately checking and setting measurements and calibrating instruments.

Precision-milled from super-hard carbide steel, each of the 36 blocks contained in the pictured SAE gauge block set measures 1-3/8″ high by 3/8″ long by its specified width.  The set includes blocks 0.05″, 0.10″, 0.1001″ to 0.1009″ by 0.0001″, 0.101″ to 0.109″ by 0.001″, 0.110″ to 0.190″ by 0.01″, 0.20″ to 0.50″ by 0.10″, 1.00″, 2.00″, and 4.00″ wide in a custom wood case.

A calibration certificate included with the set certifies it to be grade B at 68°F, which should be suitable for workshop use. This set of gauge blocks will run you $70 — we don’t even want to know what a grade A set runs.

Gauge Block Set [Jack’s Tool Shed]
Via Amazon [What’s This?]


4 Responses to Precision Machinist’s Gauge Blocks

  1. fred says:

    I’m confused by the Grade A & B
    I thought that the NIST grades were : 0.5, 1, 2 and 3

  2. @fred:

    I did a little digging and found this article about grades of flatness:


  3. fred says:

    Here’s a link to NIST on gauge blocks


  4. wackyvorlon says:

    A high end set of Mitutoyo or Starett gauge blocks can run $3,000. The blocks are usually wrung together, you wipe them with your fingers and slide them together. They are flat enough that they can push the air out from between them. The hold can be very strong. The Grade A blocks can support up to three hundred pounds of weight once wrung together.

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