KEVOS® MAKEOS · Quality
Bolt Circle Measurement over Pins
What is the distance across opposite holes of this bolt circle, measured over plugs?
Distance over plugs in opposite (or most widely spaced) holes of a bolt circle and the bolt circle diameter, from a measurement over adjacent or alternate plugs.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Number of holes | holes | Number of equally spaced holes. |
| Plug (hole) diameter | mm or in | Diameter of the plugs fitted in the holes. |
| Measured over | choice | Whether the reading is over alternate or adjacent plugs. |
| Measurement over the plugs | mm or in | Reading over the two plugs. |
Method and formulas
- θ = 360° ÷ n. Bolt circle diameter from adjacent plugs: (c − d) ÷ sin(θ/2); from alternate plugs: (y − d) ÷ sin θ.
- Even n: distance over opposite plugs x = PCD + d.
- Odd n: across the most widely spaced plugs x = (c − d) ÷ 2 sin(θ/4) + d = PCD cos(θ/4) + d.
- Example (handbook case): six 0.75 in holes 4.5 in over alternate plugs: x = 5.0801 in.
Limitations
- Equally spaced holes and plugs that fit the holes without play.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check large bolt circles with ordinary micrometers
- Find the PCD from a measurement over two plugs
- Inspect dies and flanges
Who it is for
- Quality inspectors
- Toolmakers
- Metrology technicians
What you get
- Bolt circle (pitch circle) diameter
- Distance over opposite (or most widely spaced) plugs
Interpreting the result
- Use plugs that fit the holes closely; plug clearance shows directly in the result.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 686. Topic reference; no source tables or recommended settings are reproduced.
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