KEVOS® MAKEOS · Fasteners
Bolt Pattern Hole Plan (Layout, Clearance Holes, Position Tolerance)
For this bolt circle, where do the holes go, are the ligaments, edge distances and wrench clearance enough with the holes at their largest size, and what position tolerance can I allow on the holes?
Plan for a circular bolt pattern with clearance holes: hole coordinates, chord between adjacent holes, ligament, edge distances and wrench clearance with the holes at their largest (least-material) size (as the bolt circle layout tool), and the position tolerance at maximum material for floating or fixed fasteners with the bonus available at the largest hole (as the fastener position tolerance tool), checked against the least tolerance your shop can hold.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Bolt circle diameter | mm | Diameter of the bolt circle. |
| Number of holes | Number of equally spaced holes. | |
| Angle of the first hole | ° | Angle of the first hole from the X axis. |
| Fastener at MMC (largest fastener) | mm | Largest size of the fastener. |
| Clearance hole at MMC (smallest hole) | mm | Smallest size of the clearance hole. |
| Clearance hole at LMC (largest hole) | mm | Largest size of the clearance hole. |
| Fastener case | choice | Floating: clearance holes in both parts; fixed: one part is threaded or has pressed studs. |
| Share of total tolerance to the clearance-hole part (fixed) | % | For fixed fasteners, how the total tolerance is split between the clearance-hole part and the threaded part. |
| Flange and limits | ||
| Flange outside diameter | mm | Outside diameter of the flange. |
| Flange bore (0 = solid) | mm | Bore of the flange (0 for none). |
| Socket or wrench clearance diameter | mm | Diameter the socket or wrench needs around each fastener. |
| Least ligament between holes | mm | Least metal you accept between adjacent holes. |
| Least edge distance (hole edge to flange edge) | mm | Least metal from a hole to the flange edge or bore. |
| Least position tolerance the shop can hold | mm | Smallest position tolerance your drilling process holds reliably. |
Method and formulas
- Hole k at angle start + k × 360 ÷ n on radius BCD ÷ 2; chord = BCD sin(π ÷ n); ligament = chord − largest hole; edge distances to the outside and bore (as the bolt circle layout tool).
- Floating fasteners: T = H − F for each part; fixed: T = H − F shared between the parts (as the fastener position tolerance tool).
- Bonus at the largest hole = H_LMC − H_MMC; total allowed = T + bonus.
- Example: the clearance holes may be 1 mm out of position at MMC (1.3 mm at LMC); the ligament is 59.411 mm.
Limitations
- Equally spaced holes on one circle.
- Position tolerance from fastener clearance only; mating parts need the same datum scheme.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Lay out and tolerance a flange bolt pattern
- Check a pattern before drilling
- Decide whether fixed or floating fasteners work
Who it is for
- Design engineers
- Drafters
- CNC programmers
What you get
- Hole coordinates, chord and ligament
- Edge distances and wrench clearance
- Position tolerance and bonus
Interpreting the result
- If the tolerance is too tight to make, use larger clearance holes or floating rather than fixed fasteners.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 686, 615–627. Topic reference; no source tables or recommended settings are reproduced.
- ASME Y14.5-2018 Dimensioning and Tolerancing
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Open the Bolt Pattern Hole Plan (Layout, Clearance Holes, Position Tolerance) calculator
