Version 1.0, August 31, 2001, Copyright, Hugh Jack 1993-2001

35.6 GAUGE BLOCKS

 

· The purpose of gauge blocks are to provide linear dimensions known to within a given tolerance.

 

· The requirements of gauge blocks are,

  1. - the actual size must be known
  2. - the faces must be parallel
  3. - the surface must have a smooth finish
  4. - the surfaces must be flat

 

· most gauge blocks are made by normal techniques, but the high accuracy is obtained by a process called lapping (discussed later)

 

· The materials gauge blocks are made from are selected for,

  1. - hardness
  2. - temperature stability
  3. - corrosion resistance
  4. - high quality finish

 

· type of gauge blocks

  1. - rectangular
  2. - hoke (square)

 

· there are four grades of blocks,

  1. - reference (AAA) - high tolerance (± 0.00005mm or 0.000002")
  2. - calibration (AA) (tolerance +0.00010mm to -0.00005mm)
  3. - inspection (A) (tolerance +0.00015mm to -0.0005mm)
  4. - workshop (B) - low tolerance (tolerance +0.00025mm to -0.00015mm)

 

· Original gauge block sets had lower tolerances and had a total of 91 pieces with values,

  1. 0.010" to 0.100" in 0.001" steps

 

· An 81 piece set of gauge block was developed by Johansson(s??) and is capable of covering wider ranges of dimensions.

  1. 0.1001" to 0.1009" in 0.0001" steps
  2. 0.1010" to 0.1490" in 0.0010" steps
  3. 0.0500" to 0.9500" in 0.0500" steps
  4. 1.0000", 2.0000", 3.0000", 4.0000" blocks
  5. (2 wear blocks at 0.0500")

 

· An 83 piece set has also been developed and it has the values (in inches),

 

 

· The metric set has 88 gauge blocks (in mm),

 

 

 

 

· Most gauge block sets include thin wear blocks that should be included at the ends of a gauge block stack to protect the other gauge blocks.

 

· How to select gauge blocks for an application

 

 

· To assemble a gauge block stack,

  1. 1. remove the gauge blocks required from the protective case
  2. 2. clean of the oil that they have been coated in using a special cleaner. It is acceptable to handle the blocks, in fact the oil from your hands will help them stick together.
  3. 3. one at a time, hold the blocks so that the faces just overlap, push the blocks together, and slide them until the faces overlap together. This will create a vacuum between the blocks that makes them stick together (this process is known as wringing).
  4. 4. Make required measurements with the gauge blocks, being careful not to damage the faces
  5. 5. take the blocks apart, and apply the protective coating oil, and return them to their box.

 

· When using gauge blocks, minimze the number used. Each block will have tolerance errors, and as the stack of blocks becomes larger, so does the error.

 

· Do not leave gauge blocks wrung together for long periods of time.

 

 

35.6.1 Manufacturing Gauge Blocks

35.6.2 Compensating for Temperature Variations

35.6.3 Testing For Known Dimensions With Standards

35.6.4 Odd Topics

35.6.5 Practice Problems

35.6.6 Limit (GO & NO GO) Gauges

35.6.7 Sine Bars

35.6.8 Comparators

35.6.9 Autocollimators

35.6.10 Level Gauges

35.6.11 The Angle Dekkor