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Proper way to check parallelism...

ChairsWithWheels
I have a part that needs to be parallel within .0008" to datum 'A'

We cannot fixture datum A to the granite as it has a boss, we use three ground blocks to fixture the part on three points, then sweep with an indicator.

Old timey engineer says that is the wrong way to check it, and throws a pair of micrometers on it and gets .0005".

He's checking thickness correct? Not parallelism. At this point I don't know how else to explain it to engineering...
Parents
  • The BEST way to check the parallelism is on a certified surface plate setting on blocks. If flatness of -A- is critical then use 4 blocks, set on -A- and indicate -A-. 3 blocks are "OK" for parallelism but not flatness.
    Think of it as a 3 legged chair which won't rock but seems flat and parallel, but can be much unparalleled. Hope it is being ground!
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  • The BEST way to check the parallelism is on a certified surface plate setting on blocks. If flatness of -A- is critical then use 4 blocks, set on -A- and indicate -A-. 3 blocks are "OK" for parallelism but not flatness.
    Think of it as a 3 legged chair which won't rock but seems flat and parallel, but can be much unparalleled. Hope it is being ground!
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