
My measuring and layout area...
 |
Bolt
Circles |
I have had particular
trouble accurately measuring bolt circles. An accurate method I discovered
involves measuring the Chords:

Measuring
a Chord
The two drill
bits are used to provide a reference that is easily accessed with your
calipers. Be sure the accurately fit the holes! The greatest accuracy
also comes of using the longest possible chord, so don't just pick two
adjacent holes. Here is the clever formula used to determine the bolt
circle diameter:
D = C / sin(180 M / N)
D: Bolt Circle Diameter
C: Measured Chord
M: Number of Holes Between The Two
Measured Holes
N: Total Number of Holes in the Bolt
Circle

For
this example M=2 and N=5
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Dovetails |
Dovetails are another slippery one to measure. The two
cylinder method is the preferred approach:


 |
Laser
Metrology: How NASA Measures Things! |
See my special page on
laser metrology.

Measuring Plate Flatness With A Laser Level...
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