Measuring Bolt Circle Geometry Equations and Calculators
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Tolerances, Engineering Design & Limits & Fits
Measuring Large Bolt Circle Geometry Equations Calculators
For bolt circles that are too large to measure using typical methods or the measuring tools. Measuring or determining distances for a bolt circle geometry can be facilitated using the following equations and methods.
Note: In general dimensional specification for circular pattern of features is best illustrated using cartesian (x and y) linear dimensional data rather radial and angle dimensional data (bolt circle). Current industry technologies enable or embrace measurement of linear dimensional data. Most most modern manufacturing equipment are equipped with linear displacement indicators or technology, as well, as coordinate measurement machines (CMM). All units shall be consistant and given in inches or mm. Angles (theta) are given in degrees.

Even Number of Holes Within Circle: Open: 

Illustration B 
Even Number of Holes Within Circle #2: Open: 
Illustration C 
Odd Number of Holes in Circle: Open: 
Related Resources:
 True Position GD&T Tolerance Calculator
 Tolerance Calculator Floating Fastener Condition
 Tolerance Calculator Fixed Fastener Condition
 Tolerance Calculator Projected Tolerance Zone
 Tolerance Calculator 2 Mating Features @ MMC
 Tolerance Calculator 3 Mating Features @MMC
 Tolerance Calculator  True Position
 Tolerance Calculator  Spherical True Position
 Hole / Feature Pattern Plot